2001 Xsara overheating

[sanlo]

So, i´ve had my Citroen Xsara 1.6 2001 (TU5JP4) for about 4 years and I always had some issue related to the temp. It got worse last year when it reached 108C (failed thermostatic valve) and i had to stop and *fix* it in the middle of the road. After that, its not straight overheating, but hovering between 95 and 102ºc after 20 minutes of driving. I can lower the temp by revving the engine with the car stopped.

Here are some thing that i´ve done to try to fix this issue:

• I´ve checked the fan and it seems to work correctly
• Replaced the radiator
• Replaced the radiator cap
• Replaced the water pump
• Removed and cleaned every single hose i could find. Replaced the ones that were stating to crack
• Replaced the temperature sensor, along with the thermostat and its housing
• Did a cylinder pressure test (205-215 on all cylinders)
• Replaced the head gasket (I wasn't able to see any failure point on the old one)
• Checked for leaks (found none)

With the engine hot, i tried to bleed the system and it always seems to have air (or water vapor?). bleeding it or not, the car always overheats at the same rate.
The engine doesn't smoke, there are no bubbles coming from the coolant reservoir, no oil/coolant mixing. Using Diagbox, there are no error messages related to the cooling system.

What else should I check to find the root cause of this annoying overheating issue? Thanks.

[MattBLancs]

Sorry if being daft, but just checking as is not mentioned in the bullet point list - thermostat has been replaced?

[CitroJim]

Further to Matt's question, when you replaced the thermostat, did you replace it with exactly the right type? These engines require the 'top hat's style with the plate to shut off the bypass port when the thermostat is open. Use one without and the coolant will largely 'short circuit' through the bypass port whether the thermostat is open or not, leading to overheating.

Also, what temperature is the new thermostat? at very 'hot' one (88-90 degrees - intended for very cold places) might give the impression of overheating.

It is my experience of these engines, and PSA engine is general, is that they must be bled very carefully and precisely to the letter of the procedure...

An extension on top to the header tank to temporarily raise the level of coolant is often essential and one can be made easily from a 2 litre fizzy drinks bottle and a bit of BluTak to effect a seal.

A couple of bleed sessions are often necessary.

A quick test to ensue all is bled - heater works very well and the radiator is hot all over once the thermostat opens...

If you keep on finding air at every bleed attempt then it may indicate the start of a failing head gasket. I've seen this same set of issues on other vehicles in the early stages of gasket failure...

[sanlo]

Hey there,
I´ve spent some time driving and observing this issue and still haven't found any reason for it.
One thing that I didn't mention was that I had to bypass the heater a few months ago. Maybe some air bubbles and the constant 100ºc temp caused it to fail.
Maybe the cooling system expect some flow resistance from the heater matrix?

I drove it for about 2 hours last week on a hot weather (car´s computer said it was 46ºc outside) and the temp fluctuated between 92º - 102º. revving the engine always reduced the temp almost instantly.
I'm going to try messing with the radiator fan´s resistor and relays to check if its running slower that its supposed to.

Sorry if being daft, but just checking as is not mentioned in the bullet point list - thermostat has been replaced?

Yep, a couple of times actually. I drilled a small hole on the first replacement, to help bleed the system. I replaced with another one just to be sure.

Further to Matt's question, when you replaced the thermostat, did you replace it with exactly the right type? These engines require the 'top hat's style with the plate to shut off the bypass port when the thermostat is open. Use one without and the coolant will largely 'short circuit' through the bypass port whether the thermostat is open or not, leading to overheating.

Also, what temperature is the new thermostat? at very 'hot' one (88-90 degrees - intended for very cold places) might give the impression of overheating.

It is my experience of these engines, and PSA engine is general, is that they must be bled very carefully and precisely to the letter of the procedure...

An extension on top to the header tank to temporarily raise the level of coolant is often essential and one can be made easily from a 2 litre fizzy drinks bottle and a bit of BluTak to effect a seal.

A couple of bleed sessions are often necessary.

A quick test to ensue all is bled - heater works very well and the radiator is hot all over once the thermostat opens...

If you keep on finding air at every bleed attempt then it may indicate the start of a failing head gasket. I've seen this same set of issues on other vehicles in the early stages of gasket failure...

I believe it was the right type. I bought the first one on a store and the second one online with the right partnumber. I'm also not sure about the temp specification, but i might put it on a boiling pot to be sure.
I did try to bleed the system a few times, but im probably going to try that method with the bottle and blutak just to be sure.
Last month i replaced the headgasket (found no sign of coolant leak) and really hope its not the issue.

[MattBLancs]

Last month i replaced the headgasket (found no sign of coolant leak) and really hope its not the issue.

Tell me more about the head gasket replacement:

What was changed?
What was checked? (e.g. head for flatness, and/or pressure tested?)
Symptoms leading to gasket replacement?

Hope it's not the issue too, but keen to know more to hopefully rule it out

[sanlo]

I did a compression test prior the head gasket job, with similar result on all cylinder (with the engine cold and hot).
I replaced the head gasket and I am no professional, but tried to follow the procedure by the letter. I replaced only the gasket and bolts (viewtopic.php?t=73358).
After scraping old oil and gasket material, the flatness (head and block) was checked with a feeler gauge and a metal ruler (real sketchy, but against a straight piece of glass seemed straight).

After months of trying to deal with the overheating symptoms, I was out of options and too many people said it was "definitely" the issue. The head gasket replacement was done out of "desperation" and personal curiosity.

After the head gasket replacement (and before I replaced the radiator), the heating issue was exactly the same as before. Replacing the radiator mitigated the issue and the temp never went past 102ºc.
BTW, Im using the FAP app on my phone (along with a BT OBD2 scanner) to check for these temperatures.

[MattBLancs]

Was going to ask about temperature sensor, but read first post and have seen that's already been swapped - just to check, some have multiple temperature sensors and others a single one (old version was one sensor fed temperature gauge, another sensor told the ECU, and a temperature sensor or switch drive the radiator fan. Later version is temperature information fed to ECU then from ECU to gauge and turning on radiator fan is another ECU output. From age of yours I guess it could be either method, so just to check if there is more than one?

Head gasket replacement and your method of checking seems ok given what you have available. And you've clearly not made it worse as it's no different than before!

I think I'd be removing thermostat, check what opening temperature is specified on it (the ones I've seen have it etched on) and thermometer and thermostat in a pan of water slowly brought up to the boil to see if opens when it should.

Water pump changed, not sure if there are any variants but wondering if wrong one fitted could be poor flow (thinking aloud, it may be there is only one option that fits. This is a TU series engine, don't know if alloy block and steel block versions have similar but not the same pumps?? "Reving the engine almost instantly reduced it" is what has me wondering. Never seen temperature fluctuate with engine speed like that, so suspect something about the pump functionality. Normally only thing giving rapid temperature drop is flow over the radiator, either moving again if stationary or radiator fan kicking in.


Heater matrix: on a 2001 car I'd have said it's done ok and probably could have failed regardless at that age.
Does your bypassing exclude the normal bleed points on the pipes to/from the matrix? (Tyre valve cap type normally)


Sorry, I've never driven a car in 46°C heat, not much chance of that in the "frozen north" here! So not too sure what engine temperatures would expect in such ambient conditions.

Matt

[CitroJim]

There are indeed at least two different TU water pumps but the ones I've seen are obviously non-interchangable they have different sized sprockets.

I've known the impellors come loose on the shafts and that usually causes quite severe overheating..

However, having excluded so much it may be worth revisiting the pump as the impeller could be a little loose and slipping under heavy load... That the temperature immediately reduces on revving the engine may support this thought...

I've also seen some after-market water pumps with what appear to be quite small impellers compared to the old one, maybe built down to a price and just being big enough to 'get away with it' - that could cause it too. I'm wondering if the iron an alloy blocked TU pumps are similar but have different sized impellers?

46 degrees is quite a test of any cooling system!

This is quite a puzzle.

Lastly, has the temperatures being seen on diagnostics and (assumed to be) the temperature gauge been confirmed by the use of an IR temperature sensor pointing at the top hose/top of the rad or other means of independently confirming the temperature? It's not unknown for a sensor to lie... Good point Matt on the number of sensors

[Jaf]

46 is very, very hot. I've driven my diesel xantia in that. Had to stop as the engine was at 110, poor thing. (there were 5 people in the car, with air con off to try to save the engine. Scary hot) Usually when driving at around 38/40 the engine gets to 100, which is a bit worrying but seems normal.

I don't know your engine, but are you sure it's actually getting hotter than it should? Do you know anyone with the same engine so you can compare?

Are you using a good coolant as that helps by a few degrees. Also wondering if petrol fuel timing can affect engine temperature? (It does on my diesel)

[sanlo]

Was going to ask about temperature sensor, but read first post and have seen that's already been swapped - just to check, some have multiple temperature sensors and others a single one (old version was one sensor fed temperature gauge, another sensor told the ECU, and a temperature sensor or switch drive the radiator fan. Later version is temperature information fed to ECU then from ECU to gauge and turning on radiator fan is another ECU output. From age of yours I guess it could be either method, so just to check if there is more than one?

Lastly, has the temperatures being seen on diagnostics and (assumed to be) the temperature gauge been confirmed by the use of an IR temperature sensor pointing at the top hose/top of the rad or other means of independently confirming the temperature? It's not unknown for a sensor to lie... Good point Matt on the number of sensors

It seems that this engine only have a couple of temp sensors, one that feed data to the ECU (and the ECU controls the temp gauge and fan) and one that activates at 108c and lights up a warning on the dash.
I mentioned that I replaced the thermostat and its housing but I didn't mentioned that i replaced it with the one used on a later revision. The temp sensors are a bit different, but I did test both on a pot with hot water and measured the resistance on both of them. Im probably going to install the old one and see if the issue persists.

Spoiler: show

the original one


The replacement

Water pump changed, not sure if there are any variants but wondering if wrong one fitted could be poor flow (thinking aloud, it may be there is only one option that fits. This is a TU series engine, don't know if alloy block and steel block versions have similar but not the same pumps?? "Reving the engine almost instantly reduced it" is what has me wondering. Never seen temperature fluctuate with engine speed like that, so suspect something about the pump functionality. Normally only thing giving rapid temperature drop is flow over the radiator, either moving again if stationary or radiator fan kicking in.

There are indeed at least two different TU water pumps but the ones I've seen are obviously non-interchangable they have different sized sprockets.

I've known the impellors come loose on the shafts and that usually causes quite severe overheating..

However, having excluded so much it may be worth revisiting the pump as the impeller could be a little loose and slipping under heavy load... That the temperature immediately reduces on revving the engine may support this thought...

The waterpump was replaced a few years ago and worked fine before the overheating issue. When i was replacing the headgasket, i removed the water pump to see if it was in good condition (it was, only had some light surface rust on the impellers). I didnt check if the impellers were loose, but it does have some water pressure (Before the headgasket job, I removed the thermostat and the upper hose and the engine spat coolant right as I turned the engine). If push comes to shove, I might get a new pump just to be sure.

Heater matrix: on a 2001 car I'd have said it's done ok and probably could have failed regardless at that age.
Does your bypassing exclude the normal bleed points on the pipes to/from the matrix? (Tyre valve cap type normally)

I bought the car with the heater matrix already bypassed. TBH, there is no need for a heater where I live, but I replaced the old one with a cheap unit last year. Dont know if this new one failed due to the high temp or if it was a low quality unit.

Lastly, has the temperatures being seen on diagnostics and (assumed to be) the temperature gauge been confirmed by the use of an IR temperature sensor pointing at the top hose/top of the rad or other means of independently confirming the temperature? It's not unknown for a sensor to lie... Good point Matt on the number of sensors

Yeah, I keep forgetting to bring the IR thermometer with me when I go for i drive. I'm gong to try that next time I have some time for more troubleshooting.
In any case, the intense heat that radiates from the engine bay when I open the hood tells me its a bit to hot than its supposed to be

Also, some updates:
Yesterday i did a quick check at the cooling fan and relays and it was fine. found no issue and using Lexia I was able to activate the fan's slow and fast speeds.
Today I had to drive it for about 2 hours with some heavy traffic. For the first 20 minutes the temp stayed at 90-92ºc, after that slowly rose to 101-104ºc and never went past . My "technique" of revving the engine stopped working after a while.
When I got home, I tried to open the expansion tank (with the engine still running) and it barely had any pressure on it. As soon as I stopped the engine, coolant came pouring out of the expansion tank.
I stopped and started the engine a couple of times and very quickly the temp gauge was at 90º.

Maybe it is some water bubble that is still stuck somewhere on the system? Im going to spend some more time trying to purge the cooling system just to be sure.

46 is very, very hot. I've driven my diesel xantia in that. Had to stop as the engine was at 110, poor thing. (there were 5 people in the car, with air con off to try to save the engine. Scary hot) Usually when driving at around 38/40 the engine gets to 100, which is a bit worrying but seems normal.

I don't know your engine, but are you sure it's actually getting hotter than it should? Do you know anyone with the same engine so you can compare?

Are you using a good coolant as that helps by a few degrees. Also wondering if petrol fuel timing can affect engine temperature? (It does on my diesel)

Before, the needle stayed a bit below 90º at all times before the overheating incident. I talked to some people on a Facebook group and apparently above 95º on our weather is "abnormal". The ECU doesn't have any error codes that can point at some issue with fuel delivery (TBH, I have no idea how to change it since its all electronic)

BTW, i really appreciate the help and suggestions that you are all giving me.

[MattBLancs]

Today I had to drive it for about 2 hours with some heavy traffic. For the first 20 minutes the temp stayed at 90-92ºc, after that slowly rose to 101-104ºc and never went past . My "technique" of revving the engine stopped working after a while.
When I got home, I tried to open the expansion tank (with the engine still running) and it barely had any pressure on it. As soon as I stopped the engine, coolant came pouring out of the expansion tank.
I stopped and started the engine a couple of times and very quickly the temp gauge was at 90º.

BTW, i really appreciate the help and suggestions that you are all giving me.

Few thoughts (long day and brain already gone to sleep!)

90°C normal then 100-105 in heavy traffic= sounds normal to me.

Taking expansion tank cap off with hot engine definitely not recommended! Very odd no pressure built up - would expect considerable pressure build up with engine up to temperature (and risk of scalding as a result hence not recommended!)

The high pressure helps the coolant stay liquid (effectively raises boiling point above 100°C) so is also risk of "flash boiling" if suddenly drop pressure.

That lack of pressure makes me suspect the expansion cap to an extent.

Glad suggestion and thoughts are appreciated and looking forward to getting it fixed

[CitroJim]

That lack of pressure makes me suspect the expansion cap to an extent.

Yes, good thought Matt. And if you remove the cap with the engine running and hot with the coolant just below boiling point then what happened is likely what would be seen if the cap was a bit 'iffy' or for some other reason the system is not holding full pressure.

As soon as the engine stops and the coolant stops circulating it will very quickly boil and spill out of the expansion tank once the cap is removed...

<Granny Suck Eggs Warning> The reason the system is pressurised is to stop the coolant boiling and bubbling under normal service and especially when the engine is first stopped but has no effect on the absolute temperature of the coolant. If an engine boiled every time the engine was stopped after a hot run it would be both noisy and lots of coolant would be lost each time... </Granny Suck Eggs Warning>

How often does the coolant require topping up? And how often do the fans run? How much on low speed and on top speed. Does your car have aircon and is it in regular use? Do you notice any difference with aircon on and off?

[MattBLancs]

I'm wondering if the iron an alloy blocked TU pumps are similar but have different sized impellers?

Same wondering I was having.

https://www.205gtidrivers.com/forums/to ... ter-pumps/
This suggests some alloy block TU are different to some steel block TU. Not found anything definitive yet.


(Still favour the expansion cap theory at moment, but the revving dropping the temperature thing still niggles!)

[CitroJim]

https://www.205gtidrivers.com/forums/to ... ter-pumps/
This suggests some alloy block TU are different to some steel block TU. Not found anything definitive yet.

The TU, in its long life, evolved quite significantly Matt so anything is possible After all, it's both French and a product of PSA

(Still favour the expansion cap theory at moment, but the revving dropping the temperature thing still niggles!)

Yes, I'm with you on both points... This really is quite the mystery...

[sanlo]

So, today I had some time off and didn't really wanted to drive around to do some tests.
On my garage, I planned on doing some simple stuff like jacking the driver side and letting the engine reach the operating temp. I also brought the IR thermometer to check if the sensor is working correctly like it was suggested.

Looking at the dashboard and the FAP app, the car reached 87º and the rad fan turned on. Thing is, the IR thermometer (pointed at the upper radiator hose and thermostat housing) read 74cº. Assuming that the sensor always reads 13ºc higher, it explains the car staying at 103-104 at all times on my last drive. It may be and issue with the incorrect sensor (that its also used on the Xsara Picasso) on something on the wiring.

So, im probably going to reinstall the original housing/thermostat, replace the sensor and its connector and try these tests again.

Just to make sure my IR therm. isn't reporting the wrong temp, I put a thermostat (with "89º" written on it) on boiling water and checked the temp. It opened exactly at 89º and at 100º the water boiled.

...I really should have tried this before