207 1.4 coolant overflowing

[balo0]

Hello all,

I have a problem on my 2007 Peugeot 207(VIN:VF3**************[VIN obfuscated, can be read by forum staff]): the coolant is overflowing from the expansion tank even when the cap is tightly screwed.
It all started a few days ago when I noticed some fluctuations in the temperature gauge. Thought that maybe there was not enough coolant and topped it up to max.
Drove the car and it heated pretty quickly(blowing hot air inside) but the gauge was still fluctuating. After driving for some time I stopped and opened the hood. Then I noticed that the level of coolant in the expansion tank was slowly rising and it started overflowing. Checked the cap and it was tight.
Checked with Diagbox if there were any fault codes and found a P0598 "Controlled thermostat signal" fault. So I started suspecting the thermostat.
But it's strange. The car starts blowing warm air in about 3-4 minutes after starting to drive from cold and it does not overheat. I thought that if the thermostat would fail in the open or closed position, the car would either overheat or get warm slower.

Today I cleared the fault, topped the coolant halfway between min and max levels and drove on the highway for about 40 min with diagbox recording the coolant temp. oil temp, piloted thermostat reference level and measured fan speed. While driving, the fan did not start and the temp of the coolant was maximum 96 degC while the oil temp was maximum 95 degC. All while driving the thermostat reference level was set to 99% which i found strange(but i'm not sure if this is normal?). When i stopped and left the engine idling, coolant temp went up to 103 degC, but the fan did not start. In the meantime, the coolant level started increasing as well and overflowing.

Did a test on the fan and it only works on high speed. If I test it on low speed, it does not spin at all.

Do you know what it might be? I don't want to start swapping parts without a possible cause.

Your help would be greatly appreciated.
Thank you!

[ozvtr]

All those temperatures are fairly normal for the situations that you describe, however;
At 103' the expansion tank shouldn't overflow.
At 103' the radiator fan should be running.

I know that in PP the "low speed fan test" doesn't work on some car models, but I don't know if it should work on yours.

So, on the surface I would guess that you have a combination of a bad expansion tank cap and a failure of the radiator fan to run at low speed.

I don't know about the P0598 error. It could be that the engine ECU is whinging that the coolant temperature is not tracking the thermostat position. If the radiator fan is not running in low speed, the engine ECU may be commanding the thermostat open (further) but the coolant temp is not going down?
If you clear that fault does it immediately come back? If so, I would say that the thermostat is faulty. If it only pops back up after running the car for a while, then I would say it's the other factors.

[SwissTony]

Sounds like the cylinder head gasket has failed to me. Can you get a compression or sniff rest done? It's not unheard of on these engines - happened to both my 1.4 ZX and 207!

[wheeler]

If you dont have anything to test the cap release pressure with might first be worth just replacing it anyway, there is a modified cap & it's less than £7 from the dealers in the UK.

[balo0]

Thank you for your replies. I'm starting to suspect the headgasket might be the culprit.
Today i had more time to investigate the issue. First of all i changed the expansion tank cap with a new one and it's still overflowing.
I started the car and waited to warm up. I let it warm while the engine was at idle, did not touch the accelerator. In the meantime i checked the radiator inlet and outlet hoses and noticed that they were warming. The inlet somewhat warmer than the outlet, as expected. Car heat up in a few minutes and was blowing hot air as expected. The car heat up and it got up to 108 degC and this is when the radiator fan kicked in at high speed, bringing the temperature down to about 105 degC. The fan only ran for 10-20 seconds. In the meantime, the expansion tank was almost full, after the coolant level was at the min mark while the engine was cold. I also noticed bubbles and coolant flowing on the inside of the tank. Inside the car i could hear gurgling noises, faint but noticeable. Then i pressed on the accelerator and kept the engine at 2000 rpm for 10-15 seconds, after which the fan kicked in on high speed and brought the temperature to 80 degC. While the fan was running, the coolant level in the expansion tank went down back to somewhere above minimum.
After i shut the engine off, i removed the cap on the expansion tank and smelled what was coming out. It did not smell as exhaust gases, but rather like hot coolant.
The thermostat error did not pop up again after driving over the weekend.

Does this look like a blown headgasket or just trapped air inside the cooling system?

[myglaren]

Just taken my daughters car in, similar symptoms, I noticed the gurgling some months ago when I was driving it. There was a leak though and a new thermostat housing fitted.
It carried on gurgling though but she never said, I don't drive her car often.
Then it was losing coolant again, she kept it topped up but then said last week that the bonnet catch was broken, so couldn't top it up.

She has been twice to Oxford Uni and back, round trip approx 500 miles, also uses it a lot to ferry her friend to hospital, around thirty miles a day.

They just phoned and confirmed it is the head gasket

Hopefully yours will just need bleeding thoroughly.

[ozvtr]

First of all i changed the expansion tank cap with a new one and it's still overflowing.

I also noticed bubbles and coolant flowing on the inside of the tank.

If you have bubbles in the tank when the engine heats up and the coolant "disappears" when the engine cools down, then you probably have a head gasket seal issue.
Unfortunately it may be a bigger problem than just the gasket.
While a damaged head gasket may be the problem, it also could be corrosion on the face of the head "eating" under the gasket. So it may need work done to the head or the head replaced!

[balo0]

Just did a sniff test on the cooland system. Used one of those kits with blue liquid that you put in a small reservoir in the coolant tank. Idled the car from cold up to operating temperature for about 90 min and some bubbles were coming out. The only thing is that the liquid did not change color. This to me indicates that there were no exhaust gases in the coolant.

I also tested the liquid by blowing air into it and it changes color, so the liquid works as intended.

At this point i have no clue on what's happening and what the problem is. Probably i will change the thermostat and do a coolant system refil and see where that leaves me.

If you have any other ideas, i would be glad to hear them....

[Huskyxantia]

Get the head skimmed new head gasket to your find it will be that thats giving the issues. Loads of us on here have had almost the same or known someone with what your posting about, find a friendly mobile mechanic who's good at his job and won't empty your bank accont, & get it done before winter.

[myglaren]

If the kit is showing no exhaust in the coolant and there is no oil/water contamination then it may be that the system is incompletely bled, can be an issue with some.
Park facing uphill to bleed, so that the radiator is as high as possible with respect to the engine.
Some have made a separate 'header tank' from a 2L pop bottle, bottom cut off and inverted in the mouth of the expansion tank, some method of sealing may be required. Plasticine may work, can't remember what others have used, possibly just lots of tape.

Apart from that, only an experienced mechanic could say, even then they can be wrong.

[moizeau]

Get the head skimmed new head gasket to your find it will be that thats giving the issues. Loads of us on here have had almost the same or known someone with what your posting about, find a friendly mobile mechanic who's good at his job and won't empty your bank accont, & get it done before winter.

No, don't for for the moment. I've had 4 XUD's that had the 'common' problem of headgasket failures, never had one and have put massive miles on them all, the BX19RD, 450K miles.
Keep it simple. Follow the advice on bleeding. Make sure you turn the heater on hot because air could be trapped in the matrix. Thermostat could be an issue but wouldn't cause the influx of air. Are there any bleeds high up near the scuttle?
It may be the head but eliminate everything else first.

[ozvtr]

Well, it doesn’t seem to be a head gasket problem.

I find it hard to believe that there is so much air in the system that it causes a CONSTANT overflow of coolant. Also, the engine remains fairly cool. It’s not over heating? According to my calculations, the expansion tank shouldn’t overflow (coolant boiling) until the coolant reaches about 125’C! The pressure in the system should rise to about 20psi before the cap opens. It’s overflowing at about the boiling point of water at sea level (100’C). Meaning the system pressure is not rising. Leading me to believe there is a leak in the cooling system. But the coolant is only coming out of the expansion tank cap!

Do you have a way of pressure testing the system? I still don’t think the expansion tank cap is forming a proper seal. If the new cap is serviceable what about the expansion tank itself? The cap forms a seal via the oring around the edge. Damage to the inner part of the expansion tank neck?
I could understand the engine overheating with the system not purged correctly but the engine is not overheating! At least not according to the posts so far. 90'C when running and 100'C when idling is not overheating.

[gwest]

If it like my 207 VTI then it will have a bleed cap near the bulkhead for the heater and one on the thermostat which is somewhat inaccessible and as I have found, easy to strip if you tighten it too much. And it doesn't need to be tight- it has a small O-ring that does the sealing. A new expansion tank might not be a bad investment as would a close inspection of the O-ring in the cap. As ozvtr sais you have a pressurisation, not over-heating problem.
As for the 99% signal to the heater in the thermostat that could be normal but you would only expect it for a short time if my experience was anything to go by- see below