PEUGEOT BOXER 1.9Ltr Diesel Engine Page 2


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These pages are dedicated to my experiences of the Peugeot Boxer, 1.9Ltr Turbo Diesel engine and not definitive advise. 

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1. Radiator Modification Control Switch for Radiator Fans. 

2.  Removing the Loudspeaker Panel to enable the modification. 

3. Email from: INTERCHANGE Motorcaravan Motorhome Monthly Magazine. [MMM]

4. Email Messages  Ref. overheating.

5. Radiator Over Heating    

6.  Antifreeze Change

7. Changing Cooling Thermostat.

10.  How to change the Heater Matrix 

11. The Blower Heating System    

8. Radiator and Water temperature  switch on  Radiator

9. Changing the Water Temperature    Fan Switch




Regarding my experiences of over heating, described below. I received this email from Jarle in Norway [May 2005]:

Hallo there !

I have appreciated reading about the cooling modifications in your web site.

This is because our 97 Peugeot Boxer 1,9 TD has had overheating problems since we bought it in 2003, especially in long uphills.

After having tried just about everything and even consulted our Peugeot dealer, things were beginning to look dark, but then I called at an old radiator garage, and they said that many of the new aluminium radiators can deteriorate very fast!

So I took it off, Wow! much part of the radiator was corroded and smuldred if I touched it !

After installing a new radiator, it has yet to exceed 90 degrees, and even when pulling  horse/trailer (1350 KG) upphill!

Jarle Halvorsen


I have since replaced the radiator as suggested by Jarle. The radiator on my Boxer is 90% plastic. This year we experienced no problems.
 [ June 2006 ]

See here for useful tips on vehicle maintenance:-


         In May of 2002 we travelled to Spain.  Whilst our Motorhome performed impeccably, it was inclined to over heat on the long inclines, at least this is what the indicator gauge was showing, a gradual increase of temperature.  I was worried that the fans were not cutting in soon enough or perhaps one fan was not working.

         On the Peugeot van, it has two fans operated by a three terminal thermostat at the bottom of the radiator.  The cables are then taken to a black plastic container located at the top of the radiator.   There you will find two relays inside this box.   These relays operate the fans. 

           I checked the thermostat contacts and found each terminal would operate an individual fan, and both fans were operating.  Checking these terminals is easy, Just short out one terminal to the other and a fan will come on. You will find the terminals are in a 'T' arrangement. the bottom of the 'T' is common.

           I then modified the relays to enable switch control. See the drawing below.

Drawing of Modified Fan Circuit which include LED's fitted.
The green wires and the components inside the green block is the modification.
If you have good hearing then it is not necessary to incorporate the LEDs. 

Peugeot Boxer Fan Wiring

           I decide to produce this modification to ensure I could operate the fans before the temperature got too high.

           Another concern was; The fans also cut out before the radiator temperature gauge had reduced to an acceptable level.  It is possible the thermostat on the radiator is faulty and this is to be checked. [See Changing Cooling Thermostat Mar 2004] I have since found the gauge shows a temperature greater than that at the radiator fan switch.

May 2002 the Cooling Thermostat [The garage describe it as the "Radiator Switch"] was changed without the hoped for results!

           This modification was introduced to give peace of mind while travelling in foreign lands.

           Since carrying out this modification I have received an email and drawings from Steve,, who has taken up the modification, but prefers to fit the LED's to pin 30 of the relays. This will  indicate whether the relay contacts are doing it's work. This does mean taking two cables from the relays. Pin 30 for the LED's and Pin 86 for the switch.

           You will note in the drawing, I have incorporated two diodes.  These are sometimes called steering diodes.  When the switch is turned in the up position, one fan is turned on, when the switch is turned to lower position the two diodes ensure two fans are turned on.   This arrangement was used as I was not able to work out how the manufacturer designed the relays to operate. They are located in a container, on the radiator top. 

             In the Haynes Peugeot handbook for cars and Diesel engines, the drawings show three relays to do this function!  Only two are in the Boxer relay container box.

            It would appear that the three terminal thermostat located on the radiator base, has a piston mode of operating, as the temperature increases, one fan turns on then the other, at a greater temperature.


Boxer Radiator Fans, Thermostat Switch, and Relay Container.

      Feb. 2010.

      During our tours in France Sept. 2009, the water Temperature gauge was starting to creep up again.
      So I have decided, before changing the radiator, to replace the radiator water temperature switch, which controls the radiator fans. If this makes no change, then I must consider a radiator change as they are prone to blocking up.

Radiator Water Temperature Switch

Radiator Temperature Switch, fitted into the Rad.

View of the Radiator Temperature Switch plug.
Which is fitted into the Rad. and controls the fans.
Seen bottom left of the radiator. It contains the spades which are not shown very well [Passenger side view]

Radiator Temperature Switch, cable and cocket.

View of the Radiator Temperature Switch
cable and socket which fits into the plug seen on the left.
bottom left of the radiator. [Passenger side view]

View of the new Radiator Temperature Switch ready for fitting

View of the new Radiator Temperature Switch ready for fitting

     Fitting the new Radiator switch is quite easy.  I unscrewed the radiator cap at the expansion tank. To ensure there was no pressure in the system. I then clamped the three pipes going to the radiator, to reduced any pressure at the switch location. Using a set spanner of approximately 30mm across. I unscrewed the switch device and promptly inserted the new switch. The lost of antifreeze was a few dropplets, and no air bubbles!

   I did some calibration checks of my new Temperature switch, before fitting. I have found the 1st switch comes on at 90degrees C, the 2nd switch comes on at 95degrees C. Which is close to the specification by Peugeot. This might not equate to those readings on the temperature gauge as the sensor is located at a different location. The Haynes manual claims it is fitted into the thermostat housing. See thermostat housing

     Having fitted the new Radiator Temperature Switch, I found that the Dash panel gauge showed the 1st fan coming in at 94Degrees C. So the gauge shows 4 degrees C higher than the temperature at the fan switch.

Engine Thermostat
The Engine thermostat's main job, located on the engine block,  is to allow the engine to heat up quickly, and then to keep the engine at a constant temperature. It does this by regulating the amount of water that goes through the radiator. At low temperatures, the outlet to the radiator is completely blocked; all of the coolant is re-circulated back through the engine. This can be seen in the expansion tank very soon after the engine starts.     Once the temperature of the coolant rises to between 180 and 195 F (82 - 91 C), the thermostat starts to open, allowing fluid to flow through the radiator. By the time the coolant reaches 200 to 218 F (93 - 103 C), the thermostat is open all the way.     The thermostat lies in the small cylinder located alongside of the engine oil dip stick container. This cylinder is filled with a wax that begins to melt at around 180 F (different thermostats open at different temperatures, but 180 F is a common one). A rod connected to the valve presses into this wax. When the wax melts it expands significantly, pushing the rod out of the cylinder & opening the valve.

Final Modification of Fan Switch shown below fitted to dashboard.

[Click for larger images]

Fan Switch Modification before LED's were fitted

Fan Switch Modification before LED's were fitted

Fan Switch plus LED indicators

Fan Switch LED indicators in place

Drawing with LED Lamps fitted.
[Interior Drawing of the Fan Relay Container can be seen above.]
The completed modification is seen inside the GREEN box below. So the only connection to the Fan Relay panel is to pin 86 on each relay.

Modified Drawing of Radiator Swithch

       Due to vehicle noise it is not possible to hear the fans operating.  This can be very disconcerting when the temperature gauge is creeping up.  So I decided to fit two LED lamps which will illuminate when fans cut in.  They will operate on the modified switch function and when the Thermostat Switch on the radiator cuts in.

     If they don't cut in!  Then the switch can be used.  See the above modified drawing.

    Since the modification I have found the fans do not operate until the temperature gauge is well over the half mark on the gauge, and then only one fan cuts in.  The second fan probably cuts in at the 75% mark.

     I have come to the conclusion that the gauge sender, which is located inside the thermostat housing, and the hottest part of the engine, will be of a different temperature from that of the fan operating rad. thermostat switch, which is located at the bottom of the radiator.  With an air flow through the radiator, by the time the water reaches the lowest part of the radiator it is not hot enough to operate the thermostat switch and turn on the fans. This difference delays any fan operation and the temperature will then fluctuate on the gauge. 

       Close to the Gauge Sender there is a 'Boiling Water' sender. I have not experienced the 'Boiling water' light coming on.

See this web site for explanation of the fans. While applying to the Peugeot 306 car. The explanation can apply to the Boxer. See;  There is reference to the airconditioning, ignore this. You will see the circuits are similar to the Boxer.

June 2005 The above web site is not responding!
I received an email from Richard Fenton, 14th Jan. 2008, who has been kind enough to give me information on the correct link to the Peugeot 306 car, to which I refer to above.
His input is much appreciated:

Brian - just found your site, and a great help with a couple of problems I have - many thanks

In the interests of returning the favour, I can offer the following link to replace the one you say doesn't work on the page about cooling fans.
 ( See above:

You may know this, if so please ignore - sometimes pages display the URL of a master page, rather than the actual page, which is annoying if you want to link to the subpage. A trick for getting the 'real' url for a page is to right-click the link, then open in new page or tab/. The 'real' url is then displayed in the address bar.

For further information have a look at steve's web site who had a similar problem to me:

Removing the Loudspeaker Panel.

           To carry out modifications, as above, requires removing the lower panel. This panel also secured the radio Loudspeaker.

            The three screws were removed, see the locations in the picture.  Then the panel was eased out and off.  This manoeuvre was due to the push fit pillars used on the panel, to hold the upper edge in place. [By levering it out, instead of pulling it out square, I damaged the pillar securing holders.]

See my page on installation instructions for electric windows, click here

See image page about panel removal reference, click here

Driver Side Loud Speaker Panel Removed
[Click for larger image]

Passenger Side Loud Speaker Panel

Driver Side Loud Speaker Panel

     While testing it was not possible to increase temperature for a check on Fan Number 2, although the modified switch will operate it.

Temperature Gauge Drawing

     Even though the 2nd fan cuts in at 105 degrees the temperature will increase until the radiator water cools.

The colours in the drawing are included as a reminder for myself, and not found on the gauge.
     Peugeot Specification:
Electric Cooling Fans:
Fan A;
Cutting in at 88Degrees Centigrade.
Cutting out at 83Degrees Centigrade.

Fan B;
Cutting in at 92Degrees Centigrade.
Cutting out at 87Degrees Centigrade.

As the radiator thermostat switch, at the base of the rad,  has been replaced, and the gauge does not indicate the temperatures as the specification above, when fan A cuts in, I must assume the gauge is reading HIGH or the specs. are different for the 1.9Ltr turbo engine.

     Since the check above, I have found the dashboard gauge does not equate to the readings above. The gauge does read higher. Due to the locations of the radiator switch and the gauge monitor.

Carrying out a test at the thermostat location sender, for the temperature gauge, I found the following:
@60 degrees a voltage reading of 5.20 Volts
@70 degrees a voltage reading of 5.50 Volts
@80 degrees a voltage reading of 5.90 Volts
@85 degrees a voltage reading of 6.80 Volts
[This is the stable position during normal driving.]
@ 90 degrees a voltage reading of 7.70 Volts
@ 98 degrees a voltage reading of 7.96 Volts 
The voltage readings are not normally required for van servicing, they are given as advice only.

     Travelling through France, Spain and Portugal in the summer of 2003 the fault was still apparent. This fault, while controlled by the above modification, is not satisfactory. I must follow through with Peugeot for a cure!

    Since Changing the engine thermostat, Mar. 2004, this has improved the cooling. I must assume the thermostat was not functioning as intended.

    I have changed the radiator, [ 2005 ] I experienced no problems during Jun 2006 while driving France & Italy, although the gauge did reach the 110 position on one occasion.

    In May 2014, overheating problems caused a failure in France and the cylinder head gasket had to be replaced. So I think all my engine heating problems stems from that source.

Date: 19 Jan 03

Hi George,

Engine Temperature.  Peugeot U25 Turbo-Diesel 

I was particularly interested in the letter by Anthony Vaughan, Hereford in the MMM Jan. 2003. His description of the temperature fault is exactly mine experienced on my Autohomes Wanderer based on the Peugeot Boxer 1.9Ltr Diesel engine.

Last June in a hot Spanish Summer the only respite was to turn on the heater and use the heater blower.   The navigator was not amused.

On my return I too went through all the possible solutions and fitted a three way switch to operate the fans. I also fitted LED indicators to show when the fans were operating.  I also had a new radiator thermostat switch fitted by a local Peugeot dealer.

On our next outing with the Mods fitted I found the fans never came on, only when we were stationary.  This was due to no cool flow through the radiators, and only then did the thermostat operate fan number one.  Fan number 2 checked out OK.

While I agree with the replies of GC and DN,  my conclusion is that as the temperature sender/monitor is located at the top of the engine circulating radiator circuit, it responds very quickly and gives the wild fluctuating indication as experienced by Anthony Vaughan and myself.   By the time the water in the radiator reaches the thermostat, located at the base of the radiator it is too cool to turn on the thermostat function, therefore the fans do not turn on.

My vehicle was 5 years old and had 30,000 miles on the clock when I purchased it, and does not seem to have had any major work,  so I must assume this is normal, but disconcerting all the same.

I am at the moment working on a circuit drawing that will monitor the gauge sensor and then operate the fans, as I found when driving in Continental long tunnels, it is not possible to monitor the gauge all the time, to enable me to use my override switch.

Best Regards,


George and Val Collings,
Interchange MMM

Hello Brian.
Thanks for the Email.

I rather wonder if you really have problem at all, could it be a case of your temperature gauge speaking if not with a forked tongue at least before your engine was actually overheating. The real test is are you loosing coolant. If the answer is yes, there is something wrong but if no, I may be right.

As I understand the coolant thermostat system the one in the cylinder head restricts coolant flow to the head itself to get the combustion chambers up to temperature as soon as possible (for improved emissions and smoother running) and give prompt operation of the heater. Once the head is up to temperature, coolant can also flow through the cylinder block. The second thermostat is the one at the base of the radiator and that opens when the water passing through the radiator passes above its specified temperature. Stepped thermostats control the two cooling fans with the second only operating at higher temperature. The purpose of thermostatic control of the cooling system is to keep it running within very close limits, not as cool as possible. That is why the main thermostat is at the bottom of the radiator controlling the temperature of the coolant returning to the engine.

What you have to remember is that the amount of fuel burnt by a modern diesel varies a great deal. At tick-over in freezing temperatures there is so little burnt you could probably drain the coolant and not do any harm (dont try this at home, viewers). At the other extreme a turbo diesel developing full power can generate a huge quantity of waste heat that has to be disposed of through the cooling system no matter how hot the air passing through the radiator. If the system cannot cope with this waste heat the coolant temperature rises high enough to boil and is blown off as steam via the pressure cap on the expansion tank. If you never have to top up then you have not actually overheated.

Although it is reassuring to have gauges to watch and manual control of fans, as you have found, the places they need most attention such as at the top of a mountain pass is just where you most need to keep your eyes on the road. My advice is always to get the vehicle working as the makers intended. Lets face it, that is what you have paid for.


George Collings

----- Original Message ----- 
From: Brian B. Walters 
To: Steve
Sent: Wednesday, August 20, 2003 7:27 AM
Subject: Peugeot Boxer 1.9Ltr Turbo diesel

Hi Steve,

My apologies for hijacking your Email address from the network54 forum.
From the forum it would appear you have experience of diesel engines. Can you help!

My Peugeot Boxer 1.9Ltr diesel will run normally at a temperature gauge reading just below half. On a long incline the gauge will creep up until it reaches almost the red portion of the meter. Over the top of the incline then down hill the meter reduces to the almost half position.
All this time the fans do not kick in.
Would you expect a diesel engine to show such a wide fluctuation on the meter. This wide fluctuation is worrying me. I have no experience of driving diesels before.
Incidentally the 'boiling' light never comes on.

Best Regards,


Reply from Steve:

Hi, Been there, several tee shirts.
You didn't say where your from, I'm based near the M50.

When I bought mine the temp was always high, and too high if I tried to cruise on a motorway at more than 70mph (speed limiter!)
I discovered the one electric fan wasn't working. Had a job to find out where they were controlled from. Eventually found them behind a cover which was built in to the plastic cowling on the radiator which surrounds the fans. after testing, I found a duff relay to cure that problem.
Whilst the van was running on tick over the fans were always cutting in and out which indicated poor cooling. I could have run some radiator cleaner through the rad, but on inspecting the rad I found the wavy fins on the radiator where falling away which indicates the radiator is rotten and likely to spring a leak.  Rather than risk a problem out on the road I replaced the radiator. Purchased it from at £139.99 + £10 delivery . they delivered overnight, even though I asked for normal delivery and ordered it at about 4.00pm.
Europarts were the cheapest around, and about half price of Peugeot!!!! 

Presently the fans don't work on mine. I haven't got round to investigating why as the temperature runs at normal, occasionally it rises on very steep long hills, 1st gear stuff, but I switch the heater on full blast. Basically with a good radiator (even in the hot weather we have had recently) there is little need for the fans.

You may find your 1.9ltr does run a little hotter than my 2.5 because its having to work so much harder.

I found some useful circuits etc here which may be of help:

Best regards


Hi Brian,

 Regarding the overheating problem we both seem to have with the Peugeot 1.9TD, I promised to get back to you if I found the answer - no luck yet unfortunately.

 I have had two radiator thermostat switches and one engine thermostat fitted, by three different garages, one in France and two garages over here, with no improvement, switching the fans on manually is the only way I can overcome the overheating at the moment.

 While returning home from a long journey today, I decided to have a good look around the cooling system to see if I could find some clues/causes for this malady. I noticed that after stopping and cooling the engine to lukewarm, starting the engine and noting how the coolant was circulating, the following was found ;-

 1. Water from the thermostat housing through hose to top of radiator(the flow) was very hot.

2. Water from bottom of radiator through hose (the return), to a midway point of the rubber hose was tepid.

3. Water from the engine lower hose (including 90deg metal pipe), to a midway point of the rubber hose was very hot.

The water is hot from the engine thermostat and rubber hose, as expected. Cool at the bottom of the radiator but does not get warmer (for maybe 15mins), however the other end of the pipe gets as hot as the hose from the engine thermostat. It seems there is a reverse heating from the engine on the lower pipe.

 The only things I can think of that may cause this fault is a flow restriction in the radiator or lower return pipe, can you check yours for similar symptoms?

 Regards Terry

Hi Brian, 

The info. in the last Email to you regarding my observations to the temp differential in the flow and return pipes, to and from the radiator are not very accurate. These observations were carried out immediately the engine was stopped and the bonnet opened, using my hand as a temperature gauge!!

I carried out a further test the next day (ambient temp 76f), after a run and whilst the engine was idling, using an electronic thermometer and found the following ;- (all temps in centigrade)

     After 7 miles.

1. Temp gauge         = Normal

    Temp on sender   = 71

    Temp on top hose at rad = 65.2

    Temp on bottom hose at rad = 51.7

    Temp on 90deg metal pipe flow to engine = 68.3

     After 12 miles.

2. Temp gauge         = Normal + 1.75 blobs

    Temp on sender   = 88.7

    Temp on top hose at rad  = 67.5

    Temp on bottom hose at rad  = 57.3

    Temp on 90deg metal pipe flow to engine = 63.5

    Fan automatically switched on for a few seconds whilst carrying out test.

     After 22 miles

3. Temp gauge         = Normal + 2 blobs

    Temp on sender   = 89

    Temp on top hose at rad  = 56

    Temp on bottom hose at rad  = 53.5

    Temp on 90deg metal pipe flow to engine = 80.4 (might indicate cool flow is not going to engine)

    Fan automatically switched on for a few seconds whilst carrying out test. 

On the lower hose (return cool flow to engine) about the midway point, there is a welded joint with a small hose, maybe a take off pipe going somewhere. I do wonder if there is a second thermostat somewhere in the lower hose, or some sort of device which may restrict the cooled water flow back to the engine, if so, this would account for the increase in engine temperature we are both experiencing.

George Collings refers in the Email to you "The second thermostat is the one at the base of the radiator and that opens when the water passing through the radiator passes above its specified temperature. Stepped thermostats control the two cooling fans with the second only operating at higher temperature. "

If what he is eluding to is true, then this second thermostat could be the problem.

I have a normal line and blobs on my instrument temp gauge, normal indicating (I think) 70,  N+1 blob = 80, N+2 blobs = 90 and the N+3 blobs (red) = 100, which seems different to your illustration of normal equal to 90.

My first fan switches on at 88.7 on the thermostat/sender housing around two blobs above normal on my instrument panel, seems about right and would indicate an engine temp of 85 to 90, the second fan has never switched on to my knowledge, but checks out OK.

I have a feeling the engine thermostat should open at 70 which appears to correspond with the normal reading on my instrument temp gauge, as the temp moves up to around two blobs above normal, approx 85 to 90 on the thermostat/sender housing, the first fan switches on. [ The thermostat in the engine is specified at 83C]

The engine has never boiled and it doesn't use water, but it would be nice to be able to find out why the engine temp appears to fluctuate so much.

I am fairly sure that when we went to Germany at the end of August 2001, the ambient temp was equal to our experiences just recently, the vehicle being new, the temp gauge stayed on normal the whole trip (70 degC ?).

Regards Terry


Hi Terry,

Today I was talking to my Brother who has spent all his life in the Motor Trade, now retired. He now spends most of his time delivering and returning leased vehicles back to his employer.

His opinion is we haven't a problem, as long as the gauge does not go into the red, and the boiling light does not come on. His opinions are based on the same as George Collins of MMM fame.

Best Regards.


Some more advice from someone who's Email address I've lost!

Until very recently I had an Auto Sleeper Harmony Boxer and still have two Citroen cars all fitted with the Peugeot/Citroen 1.9TD engine.

The indicated running temperature for all three was/is fairly constant (a little above 80 deg C) even when driven hard on the open road. In slower traffic the fan usually comes on at about 5 deg above the normal temp and always long before the red zone is reached.

So compared with my vehicles yours appears to be behaving slightly abnormally. I say "appears" because your problem may be just a faulty temperature sender and you don't say if you are loosing engine coolant.

Access to a digital thermometer with a small thermocouple probe, capable of 100degrees C,  will allow you to check your system out by monitoring actual fan switching temperatures whilst the engine is idling.
 (Noting the obligatory caution about moving parts and hot surfaces if you DIY)

Workshop Manual data for my cars suggests that the fan should switch on at 90-95 deg with the second stage switching at just over 100 deg for a two speed unit. Anything higher than this may indicate a faulty switch or connection in the fan electrical circuit.

I'm not sure, and can't now check, if the Boxer has a single or two speed fan. If the latter, and yours is not switching until 100 deg or higher, then the problem may be due to either a faulty two-speed thermal switch or its terminals are corroded causing incorrect/intermittent operation. Such switches, located as they are close to the front of the vehicle are not well protected from the elements. I have had connector problems on an earlier non diesel vehicle which was cured by cleaning and then protecting the terminals with a little silicone grease. Hope this helps.

Regarding the above, I have since found the terminals as quoted to be corroded with blue gunge, and have cleaned them with improved running conditions.

Radiator Over Heating

Below is some correspondence I had from Ken, who had problems with his Renault Trafic.

 I have included my reply to him as I feel many of the points could apply to the Peugeot Boxer!

----- Original Message -----

From: bowker[at]hesquarecottage[dot]com
To: brian
Subject: T1400 overheating problems, again ...

Hi Brian,

Ken Bowker here.

I've had endless overheating problems with my T1400 and I wonder if you can help.

Changed so far, after three expensive incidents, are the radiator, water pump, thermostat (twice), thermal switch and the two main rad. hoses, and I've fitted your switch mod to the fan, which was the only thing that got me home today (see below), because the fan wasn't working to order - thank you for that.

After the rad. change we did a few hundred miles including a fair bit of city driving without incident but then returned home and the van has been sitting idle for ten weeks or so.  Today I decided to give it a bit of a blow - and it overheated in four miles of open road.

The radiator is not becoming hot - practically everything else is, however.  I didn't check coolant level before I set off, but there's not too much in there now!

The Russek manual is a vague on the bleeding procedure for the T1400, and indeed if you look at the instructions for the smaller petrol engine they contradict each other - do you still have a copy of the detailed procedure available, and if so, would it be possible for me to get hold of a copy ?

Amongst other things Russek tells you to 'fill the radiator' - and in places mentions a radiator cap - but apart from the expansion bottle my Renault doesn't have a conventional cap, so how is the rad. initially filled?

One Renault mechanic on one of our many callouts said that if the van wasn't used for a couple of months then airlocks were likely to form because (I quote) the 'cooling system is a crap design' ... is this true (about the airlocks, not his opinion of the cooling system)? Surely if there are no leaks the coolant should stay in place in  a pressurised system - so if there were air locks, would this suggest a slight leak - and if so from where, since there's no sign of leakage under the van ?

I do hope you can help - I've been ranting about Ford Transits today ...

Kind regards

Ken Bowker

Hi Ken,

I've followed you concerns via the rtmr[] emails, regarding overheating.

I am sorry to hear about your problems. I know how frustrating it is as I have had a problem with my recent acquisition.

My first reaction was to say you have a water pump problem, but you say this has been changed recently!

My experience has been that the thermostatically controlled fan very rarely turns on, perhaps when you stop for awhile with the engine running and no air through the fins. It is because of this that I introduced the switch to make sure I had the facility to override the thermostat switch. I was pleased to see it helped you.

Back to your problem, if the radiator is staying cool then it is doing it's job, even though the fan is not turning on. To check; does the top hose get hot and the bottom hose is cool? That is OK, then the fan will not turn on.
[ Regarding my last comment; this could be wrong! If the radiator is blocked then with no circulation the radiator fan switches would remain cold and not turn on the fans!. This is because they are located at the bottom of the radiator. A engine with no circulation would heat up
[ naturally] and show as a overheating engine light. This can easily be missed if the engine panel meter is not working correctly.]

OK about the only access to the rad is by the expansion tank, that is normal. It's the same on my Peugeot diesel van.

That bit about after a 'long stay over' [Storage?] causing it to boil! I never had that problem with my Eclipse, although I used to run it every fortnight during the winter layover. Ten weeks seems a long time not to run the van, Ken!

Next drive down to a local garage, and ask them to check if they can detect any exhaust gasses in the rad expansion tank. This is to check if you have a gasket 'Blown' problem. As this is the next step to take.

I did read somewhere that the Renault van engine rad must be drained in a certain order and filled in a certain order, but I can't find it amongst my info. Sorry, Ken.

So to recap, the water pump must be checked and ensure the pump drive belt is taut, and no exhaust gasses in the rad expansion tank.

I'm surprised, John has not come up with something for you as he has spent a long time on the Renault vehicle.

Regarding the procedure for draining and filling, I'm afraid the handbook went with the van and I have no other information.

I recently purchased from a boot sale a renault 25 hand book, it applies in many ways to the renault trafic van engine.

I shall send a copy of the cooling system.

Looking at it I would say the procedure to fill the system would be.

1. Remove the expansion bottle cap. Drain down the system first.  You could take off the bottom hose to do this. Then replace it when empty. Save the fluid for further use if you know it is OK.

Note: In the renault handbook I have, it says;

If the coolant has been neglected, remove the cylinder block drain plug and place a cold water hose in the radiator top hose.

Flush the system through until the water comes out clear from the drain plug hole and the radiator hose.  If contamination is severe, the radiator may have to removed and cleaned out.

2. Reconnect the radiator hose and secure the jubilee clip.

3. Take off the top hose.

4. Fill the system via the Expansion bottle, take off bracket and hold as high as possible, fill slowly to ensure any air has a chance to expel.

5. When water is seen at the drain plug screw up tight.

6. When the water is seen coming from the top hose, connect to the radiator and secure jubilee clip, continue to fill slowly, giving any air a chance to bubble out as the expansion bottle is reached.

7. Fill expansion bottle to max. mark.

8. Fit expansion bottle to it's bracket.

9. Start and run engine for 15mins or more at fast idle, until cooling fan cuts in.

10. Switch off engine and allow to cool, preferably overnight.

11. Next [day] top up expansion bottle with coolant and run engine with fast idle and ensure the fan cuts in and remains at cool level.

I assume all the time that the filled liquid is the correct antifreeze. It is essential that an approved type of antifreeze is used. to ensure the antifreeze and lubricating properties are maintained. Also use antifreeze which will protect aluminium engines from corrosion. This should be done every two years or every 40,000 miles.

Fault Diagnosis:

'Cooling' Overheating:

1. Insufficient Cooling in System.

2. Pump ineffective due to slack drive belt

3. Radiator blocked either internally or externally.

4. Kinked or collapsed hose causing coolant flow restriction

5.Thermostat not working properly.

6. Engine out of tune.

7. Ignition timing retarded or auto advance malfunction.

8. Cylinder head gasket blown.

9. Exhaust system partially blocked.

10. Engine oil level too low

11. Brakes binding.

12. Loose hose clips.

13. Hoses perished blocking flow or leaking.

14. Expansion Tank pressure cap defective.

15. Cracked cylinder head or block.


Block Rad Drain image:

Me again!  Airlocks are funny creatures, they have a head for heights, but they can't climb down from them and can therefore remain trapped.  To demonstrate this, find a piece of clear plastic tube part fill it with water, seal the ends- then hold it with the closed ends downwards in the shape of a horseshoe, the top of the inverted "U" is empty.  Imagine this in a closed cooling system, air expands at a different rate to water when heated so the airlock expands pushes heated water out usually in the form of vapour, hence loss of water, but the crucial point is the airlock remains and when you replace the water, the airlock is still at the high point(s) and so the cycle continues.  Therefore, all air must be vented from the highest point in the cooling system

Just a thought from Technical 2.  Almost all overheating problems, given that all the component parts of the cooling system are in good condition, are due to airlocks.  These are difficult to avoid if the wrong technique is used to refill the cooling system.

First of all, the front of the vehicle must be raised, either on ramps or jacks and axle stands so that the engine is tilted back, then the header bottle is unclipped and raised as high as the connecting hose(s) will allow and secured in place then the system can be refilled.

There should be a bleed screw on the higher of the two heater hoses next to the heater box, and this should be released, as the fluid goes in air can be heard hissing out.  When fluid bubbles out of this bleed valve it should be closed off.  This valve is quite often a casualty of hamfisted servicing, and as it is plastic can be broken, and therefore removed and not replaced, if this is the case the heater hose should be slackened and eased off of the radiator spigot when fluid appears, pushed back on again.  Needless to say, this is usually a two man job.  Hope this helps,

Doug. Meatcher from

Subject: Peugeot Diesel Engine - Antifreeze Change

  Hi Robert, I have a 1.9Ltr diesel in a Boxer Van. [A Motorhome] The instructions say to undo the drain hole in the side of the engine, for antifreeze change. I can't find it. Have you any ideas. I have had the antifreeze changed by a local garage but am not confident. When I drove the vehicle home the low level coolant light came on and I had to top up!

Hi Brian,

My apologies for the delay in replying to this message as I thought you had sent it to the wrong person. There is usually a drain plug on the rear of the engine at the flywheel/clutch end which is used to drain the block.

There is also a plug or tap at the LH Side base of the radiator or you could remove the bottom RH Side hose from the radiator. [ This is looking at the front of the vehicle. I found removing the bottom rad. pipe the easiest. ]

[ I have since found a flat head plug on the drivers side of the radiator, but it is difficult to get at for draining purposes.]

Normally draining of the system is done via the radiator for adding or changing of antifreeze only. Not many people bother with undoing plug and draining the block but you should, to do the job properly.

The common mistake on refilling the engine is not removing the air as you fill. You should undo the bleed screws slightly and let the water flow out until no air bubbles visible then shut that bleed screw.

Bleed screw for anti-freeze change

There is/should be a bleed screw on a pipe at rear of engine where it goes through bulkhead to the heater. If original hose has been replaced with none Peugeot hose, as it is a straight hose, this bleed screw may not be present.

There are usually two bleed screws on the thermostat housing, one at back and one in the middle of housing, [ I have found removing bolt No. 13 in the picture above was enough to remove the airlocks ]   again water should be allowed to escape from these until no air bubbles visible. There is also a bleed screw at the top RH Side of the radiator, again dependant on existing or replacement radiator whether fitted.

The problem with not bleeding the system properly is that the system looks full but when engine heats up the air expands much more than the water and the air is pushed out of the system or to the highest point as the coolant circulates.

Then when system cools down your coolant level is lower due to the air loss from lower down in the system.


Fill and bleed system as above.

Start engine and run until hot enough to have the cooling fans cut in and then off.

Switch off engine and allow engine to cool sufficiently for you to undo the radiator cap with care. Use a rag wrapped around cap and undo very slowly.

Check water level and top up with correct antifreeze mixture. [  I used a 50% mix.  If the thermostat is working correctly,  the radiator will not fill until the thermostat opens up when engine is hot.  If the radiator fills up during anti-freeze change, it means the thermostat is open, then consider it faulty, as it should only open and flow when engine/anti-freeze is hot.]

If you have a model vehicle with expansion tank fitted to radiator obviously the coolant level is checked there and not at radiator.

Hope this long explanation helps to fix your problem.

Your vehicle was OK before the coolant change so correct bleeding should fix this problem.

Do not drive with low coolant in a diesel engine as this can be a very expensive mistake.


7. Changing the Cooling Thermostat.

Engine Thermostat
The Engine thermostat's main job, located on the engine block,  is to allow the engine to heat up quickly, and then to keep the engine at a constant temperature. It does this by regulating the amount of water that goes through the radiator. At low temperatures, the outlet to the radiator is completely blocked; all of the coolant is recirculated back through the engine.
   Once the temperature of the coolant rises to between 180 and 195 F (82 - 91 C), the thermostat starts to open, allowing fluid to flow through the radiator. By the time the coolant reaches 200 to 218 F (93 - 103 C), the thermostat is open all the way.     
The thermostat lies in the small cylinder located on the engine-side of the device. This cylinder is filled with a wax that begins to melt at around 180 F (different thermostats open at different temperatures, but 180 F is a common one). A rod connected to the valve presses into this wax. When the wax melts it expands significantly , pushing the rod out of the cylinder & opening the valve.

After cooling problems it was decided to change the Thermostat in the engine block. See the photo for location of the Thermostat.

Thermostat location and housing cover.

Thermostat Location and housing

Click on picture for detailed information

Method of removal:

Drain coolant into a container for use again. [ As there is no draining point on the Boxer, I removed the bottom hose from the radiator. ]

Unscrew the three bolts on the thermostat housing cover.

Take out thermostat and fit new one. I found I was sold an incorrect type, so I suggest it be removed and then compared at the suppliers before purchase.

Replace the antifreeze coolant. [ See emails received above for recommended method.]

The above is the simple method, on my engine the bolts could not be removed. To ensure they did not snap, a new housing cover had to purchased, as the original was removed the hard way. i.e. hacking it of, gently, to work on the bolts.

In fact due to the bolt problem we had to remove the complete housing assembly off the engine block, behind the thermostat housing cover,  and work on it at the bench. Only then could the thermostat and the antifreeze coolant be replaced.

I have been advised to slacken off the securing bolts occasionally, to ensure any future repair can be done more easily. Or, ensure the bolts are secured with a Torque spanner at the correct reading.


How to remove the HEATER MATRIX

[ Information as supplied by FRANK of fame  who has a Petrol Boxer]

I recently had to replace the heater matrix on the Boxer's heater, I was a bit reluctant to do this job as I had heard tales of having to remove the whole of  the dash in order to access the heater.
I came across a posting on an internet forum which gave me a enough encouragement to tackle the job, The poster was working on a diesel Ducato which was a bit younger than my Boxer so there are some differences.

Anyway, I am indebted to MYTHING on the Fiat forum, who unknowingly gave me the confidence to tackle the job and whose words are included below in blue italics:

Open bonnet and remove two hoses to the heater,

The hose clips on mine were the original crimp on type and were removed by twisting the tag end back on itself with long nosed pliers. These were replaced with worm drive clips on re-installation.

and three 10mm nuts, this will allow a triangular plastic retaining plate (10" x 8") to be removed.

I would not call the shape of this plate triangular and mine isn't plastic but you can't miss it as you've just disconnected the pipes going in to it. There is a sponge "gasket" behind this, around the two pipes from the matrix, I am not sure what this is supposed to do as it is too slack to do any sealing? remove this and keep safe with the plastic plate for replacement later.

I also removed the wipers and the grille to allow access to the air intake so I could jiggle it from that side if need be.

Remove two screws holding hazard warning panel and lift panel on to dash. 
Open glovebox and remove two screws just inside the lid facing down

There is also an allen headed screw on the end of the upper dash to remove, you can't see it unless you open the passenger door.

Starting on the nearside, remove screws holding lower dash, four in total. 
Go to drivers side and remove screw from lower dash three in total,

The lower panels on my van are in two parts, I didn't remove the driver's side lower panel.

remove the radio and ashtray, remove two small phillips screws and remove ashtray holder.

Go to the gear lever, prise the bottom of the gaiter away (it has a large square sprung retaining clip) then remove the screw immediately behind the gaiter, once this screw is removed the plastic gear lever surround can be lifted off.

On the floor under the gearlever is a kick panel in front of an ECU, remove 4 x torx screws holding kick panel,

My van just has a guard  around the gearchange cables where they go though the floor, I left this in place when I was removing the heater as I didn't think it would be in the way, but it was! I managed to fiddle the heater around it but I slackened it off and swung it to one side before replacing the heater to make life a little easier.

and three 10mm nuts holding ecu, move ecu to under the clutch pedal (do not unplug it), under the glovebox is a little flat electrical box, remove small bolt and clip out of the way.

The ECU on my van is under the bonnet and I did not disturb the flat plastic box or any of the fusebox connections. I did unplug the various components, switches, etc as I removed them after taking a photo to show which wires went where.

Remove 4 x 10mm nuts and lower the gear lever to the floor (leave the cables attached). Unclip the wiring loom and all the connections under the glovebox, and tuck it out of the way, remove 10mm bolt on nearside wheelarch, 10mm bolt set back in the centre and 10 mm bolt under the gear lever position,

There was also a 10mm nut on a captive stud at the bottom centre of the heater, and the bolt near the nearside wheel arch had a nut behind the bracket.

Remove the two screws holding the heater panel to the dash, 

Pulling the heater control knobs off revels a small screw under a bit of sponge under each one. Remove these three and the two mentioned above to allow the front of the central portion of the facia to be removed. The heater control panel can now be removed from its bracket by removing two screws on the left side and two from underneath. Then you can unscrew the bracket from the heater box.
I disconnected the heater control cables at the panel end at this stage. 

pull the now loose heater box forward and manoeuvre it left. 

Drop the heater box out, just took you 25 minutes and a real struggle, refitting is just as bad, take photos as you strip it and make notes, otherwise you will forget something and have to remove parts again.

I have to say that if MYTHING thought that was a real struggle then he hasn't done some of the jobs on vehicles that I have :. I found it much easier than I had psyched myself up for and quite an easy task really.
I agree about the photos though, digital cameras are marvellous for this kind of work and I took loads of photos as reminders of how things go back together. 

Ever since I've had the van, it has lost a little coolant over the course of a few weeks, I never figured out where it was going until now as I could not find any leaks, and it didn't lose enough to cause concern. I removed the heater as it had developed a serious leak, not only could you smell the antifreeze inside the van, but the demister actually made the windscreen mistier. There was about ¾" of water in the bottom of the heater casing, I removed the blower to make drying the casing easier and found that the heater was much lighter and easier to handle with it out. I decided to leave it out until I had replaced the heater in the van.

I have never been impressed with the heating / demisting performance of the van and there was always an untraceable draught in the front of the cab, but it seems like everyone else had these problems so I put it down to a design "feature".

Once the heater was out, I could see that the air intake has never been properly sealed to the firewall. Although there is a channel on the flange which looks like it is supposed to take a seal, no seal was fitted. Perhaps this is where the draught came from?  Time will tell as I made and fitted a sponge seal to go around the flange in this channel.

Below the outlet to the demister ducts is an open "port", going by its position, its only function appears to be to blow air behind the pedal box? It looked like it should have been blocked off but was a faulty moulding. I covered this with duct tape to increase pressure to the demister vents, it can be removed if required.

Heating to the passenger footwell  has always verged on non-existent but OK  for the drivers side. I found that 4" below the open port mentioned above (driver's side), there was a 2" square hole cut in the casing, 3" below this was another 1 ½" square moulded port, 2" further was another moulded port and finally, after another ½" was the last and largest outlet, pointing towards the passenger footwell but had a "barrier" of plastic impeding the flow of air.

I decided to make a couple of modifications to try and get some heat to Dot's side. 

I taped over the 2" square hole ( which looked like it had been cut out with a Stanley knife) and opened up the next one to 1½" x 2" (with a Stanley knife). I then taped over the next port which I assume is meant to direct air down the middle of the van and cut away the "barrier" to hopefully give an unimpeded airflow across to the passenger footwell. If this doesn't work, I'll try to get some suitable ducting rigged up and duct the air across to her footwell.

The blower heating system

The blower heating system is controlled by a relay, which can be seen below the fuse panel. This does mean taking off the front/loudspeaker panel to get at them. I'm afraid I don't know the exact position of the relay. [ Must do that one day  ]

The heater controls etc, are controlled by fuse 13.
The heater Panel indicator lamp is controlled by fuse 1. Check these first.

To Fault find a particular relay: Identify one black relay type. Purchase that relay. Then fit it into different positions one by one, checking the heater functions when fitted.

You will find that a couple are of different colours. Worry about those if my suggestions don't work.

I have enclosed/attached drawings to give you some idea on the functions.

The description of numbers can be found here:


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