Thermostat housing leak / seal

Does the GTA turbo thermostat provide a mechanical seal for the housing when assembled?

I have a slight leak from the housing but currently running sans thermostat so wondered if this is why? If anyone knows torque values for housing bolts that would be useful too.

Does the GTA turbo thermostat provides a mechanical seal for the housing when assembled?

The seal for the thermostat housing is the neoprene grommet that sits around the rim of the thermostat. It will only be effective when fitted to the stat.
As you are going to have to remove the top, just refit the thermostat you got from Simon Auto's with the grommet fitted (see old stat) and give it a go.
If you have not drilled a small hole in the stat, just go for a short run to get the temperature to normal, allow to cool and top up if necessary.
As there is a grommet gasket fitted, you do not need to torque the bolts, just tighten up normally, the grommet will seal the joint.

Do you know if it was the stat yet or insufficient bleeding? If it's the former then buy a new stat and fit, if it's the latter then pop the old one back in and give it a try. Should be easier now to diagnose.

And yes as John said, it's the rubber grommet that forms the seal. So you really need the stat in there to hold it in the correct shape. Does that make sense?

Thank you guys, that makes perfect sense. I was glad to find this was the source of the new leak.

I still haven't fully tested the stat, but now have a thermometer to do so. Boiling pan on stove, here I come. Should it begin to open at it's rated 88 C or be fully open by then?

If it tests ok, I will drill the jiggle hole before refitting.
Cheers

Ok, so I've done the boiling pan test on the thermostat, still not entirely sure it's behaving as it should.

Not much happens at 88C. Heating slowly, and around 92C first crack appears to open in the stat. Prob only about a mm or so gap though. Needed to be held at 92 for a little time for this to happen.

Keep heating to nearer 98C and eventually the crack opens up to about 10mm.

So the stat does open, but is it late and slow or does this sound normal? Anyone got a known working one to compare it to?

Sounds like it's a bit lazy to me. I've got a known working one but no thermometer to test with but it's best to put two alongside each other and compare.

They're only 20 quid or so new.

I can put it in a pan and take some pics if it helps though.

Sounds like it's a bit lazy to me. I've got a known working one but no thermometer to test with but it's best to put two alongside each other and compare.

They're only 20 quid or so new.

I can put it in a pan and take some pics if it helps though.

Well, if you get the chance and can be ar$ed, would be good to see how far it is supposed to open.

Where's another source apart from Simon Auto.... no point buying from same batch I suppose. Renault dealers?

#WARNING# possibly the dullest video ever....

https://youtu.be/WkbVthvXohM

Look ..... if you are thinking of sending it back to Simon Auto's, you will have to know if it is really faulty or not, and as we have ascertained that the system was not bleed properly, it would be wise to try it again having bleed the system to prove that it is actually faulty. As the stat is not in place at the moment, the stat housing will be full of coolant. Remove the stat top and fill to the brim with coolant ( the hole is not necessary as the housing is full) then put the stat in place with its sealing grommet and replace the housing top. Top up the reservoir and go for a run.
Only then will you really know if the stat is faulty or not. The job should only take you 15 mins or so ....... much less time than messing around with pans of hot water and thermometers.
If it is faulty then you can send it back for another one ...... I have a Simon Auto's one in my Alp and it works perfectly.

Greg, I think John's right in that you haven't answered the first question in the puzzle As I said previously:

Do you know if it was the stat yet or insufficient bleeding? If it's the former then buy a new stat and fit, if it's the latter then pop the old one back in and give it a try.

If you know it wasn't properly bled before then we have to eliminate that as much as any issue with the stat, and logically it's an easy first test.

Having said all that, here's some pics of my old (good) stat:

20151020_201621.jpg

20151020_201641.jpg

20151020_201701.jpg

Even before it's boiling you can see it will start to open, and should be cranked pretty open by the time it's simmering in the last pic.

However, you can't qualify that the stat works from pictures (or even a video really) unless it's totally gone. It's only when you know that the system is bled that you can move onto the next step - and then really only when you put a good working one directly alongside the one you suspect of being faulty.

This one has the jiggle valve by the way, so goes some way in mitigating against the bleed problem.

And Simon Auto ones are fine I'm sure. If you do trace the fault to the stat then it's more likely to simply be a duff example than any actual quality problem. It does happen occasionally, but pop it in and try it with a bled system first.

Look ..... if you are thinking of sending it back to Simon Auto's, you will have to know if it is really faulty or not, and as we have ascertained that the system was not bleed properly, it would be wise to try it again having bleed the system to prove that it is actually faulty. As the stat is not in place at the moment, the stat housing will be full of coolant. Remove the stat top and fill to the brim with coolant ( the hole is not necessary as the housing is full) then put the stat in place with its sealing grommet and replace the housing top. Top up the reservoir and go for a run.
Only then will you really know if the stat is faulty or not. The job should only take you 15 mins or so ....... much less time than messing around with pans of hot water and thermometers.
If it is faulty then you can send it back for another one ...... I have a Simon Auto's one in my Alp and it works perfectly.

I tend to agree with you, although I don't think it's quite as black and white as knowing that the system wasn't bled correctly last time. Bleeding does not appear to be an exact science. I did follow the instructions in the workshop manual and take things very slowly (bar the 5L container). Several test drives and bleeds, warm ups and downs were completed before using in anger and I still had a blow out of a hose.

Since removing the thermostat, things have gone (mainly) well. Temperature has never risen above the 90 more than momentarily. I just need to do a bit more testing without the thermostat and that's why, even if this one might be OK, I haven't rushed to put it back. The £20 return value of the thermostat is negligible so I will drill the jiggle and try the valve now that I'm happy it is opening. Although we can't see temperature, Darren's thermostat appears to open a similar amount so that was very useful to know. What I didn't want to risk, was any further avoidable hose bursts that might have been due to a thermostat fault. So far, I've been lucky in that I was able to repair / replace burst hoses with my modest skills. Next one might be a pig to reach without transporting the car to someone else.

I'm attempting a logical approach to understanding this car and its idiosyncrasies; trying to discover cause and effect by only changing one variable at a time and hopefully learn some solid facts. The way I see it at the moment is, the overheat / blow out events may have been due to the following:

1) Root cause = Incorrect bleeding, therefore airlocks, therefore overheat, therefore too high pressure therefore weakest component in coolant system fails

2) Root cause = Slow / failed thermostat, therefore overheat, therefore boiling, therefore pressure, therefore weakest component in coolant system fails

3) Root cause = Old hoses / pipes not up to the job of normal operating temperature / pressure, therefore leak / loss of pressure, therefore boiling / airlocks, therefore overheat.

4) Blow by issues in engine, therefore cooling system overpressure, therefore weakest component in cooling system fails.

Or a combination of some or all of the above!!

By leaving the thermostat out, I was hoping to rule out 2) above. Of course, I might also be ruling out 1) at same time, especially as there was no jiggle in thermostat.

Having replaced a few hoses and finding cooling system reliability on the road, things were looking up... until I went to track. The good news is that temperatures were controlled well during track driving time, never saw any overheating whilst driving. Sadly, as I pulled in from the 1st session, the replacement header tank sprung a leak from its seam (I risk I knew about - but stupidly forgot to pack the original, a mistake for which I'm still kicking myself!). So 15 minutes of constant 4-6k revs and things were OK. As soon as I stopped, the latent heat build up caused pressure enough to break the header tank. I'm hoping the tank was really substandard and failed at pressures less than the normal cooling system can handle but don' have any way to measure this. During cooling down, my main hoses are pretty solid. Have to squeeze pretty hard for any deflection. Is this normal?

Road driving cannot re-produce that level of work (safely) so unfortunately I'm only a little further forward in figuring the root cause of previous issues. The original header is back and I want to do a bit more testing without the thermostat to make sure temperature is still under control. Once I'm happy, will use your idea of placing the stat in the housing to keep the top hoses full and test again.

Meanwhile, new style wiper arms just arrived from Simon (had one snap on way home, luckily passenger side) along with a new V6 turbo window sticker to replace the near side one which was looking a little tatty. Apparently it might not rain tomorrow so perhaps a few more test miles then.

Having said all that, here's some pics of my old (good) stat:

Thanks Darren, seems to open a similar amount to mine so very useful.

[Alpineandy]

Some years back I changed the thermostat in one of the A310s (senility's getting the better of me as I can't remember which one, but not relevant to this thread!!!). I went to the local motor factor and said 'I want another one of those' whilst plonking the old stat down. 2 minutes later the guy came back with a new one saying 'It's from a Granada, isn't it'.
Can't tell you which model but it fitted and I haven't had a problem since (although it could be in the Spanish car and they're chasing their tails trying to sort it like you are..... but if it was that one, it wasn't a problem for 5+ years with me).

Having said all that, here's some pics of my old (good) stat:

Thanks Darren, seems to open a similar amount to mine so very useful.

I've watched your video and to be honest I don't think it opens quite as much, and does appear to be slower. In my first pic it's already open 1mm and there's almost no bubbling in the pan, yours appears to need more heat to start opening.

I'm not saying for sure that it is that, but I think if you can first rule out that the system is bled fully, then if you're still seeing issues I'd move back to the stat being the probable cause. I mentioned before that I had a similar issue years ago buy hey, it worked when tested in a pan; it was only when I put another alongside it that you immediately spot the difference and resolve the problem.

Keep plugging away, I'm sure you'll crack it. All part of the challenge!

..... 4) Blow by issues in engine, therefore cooling system overpressure, therefore weakest component in cooling system fails.

It might be worth having a Gas Test done on a sample of your coolant ....... now, I have no experience of this test, but it has been mentioned before on this forum. My understanding of this test is that it can prove that there is what you call, Blow by, as gasses are absorbed into the coolant which the test can confirm or otherwise. Other members should be able to tell you where or how this test can be done.
The other thing you can try is to suspend your original stat and your new stat in water and heat, that way you can see if they open together.
BTW, if you do the "boil water" test on stats, they must not be sitting on the pan base as direct heat will conduct into the stat body and affect the test, hence my mention of suspending the stats. Secondly, you should stir the water with a wooden spoon so hot spots in the pan are eliminated .... especially if you are using gas as your heat source. If you have a ceramic, halogen or electric spiral or flat plate hob where the heat is equally distributed over the pan base, so much the better.
Also, if you do do this stat test and want to use your thermometer, do not allow it to touch the metal bodies of the stats ..... just in the water but keep stirring

I've watched your video and to be honest I don't think it opens quite as much, and does appear to be slower. In my first pic it's already open 1mm and there's almost no bubbling in the pan, yours appears to need more heat to start opening.

Darren ..... the stat in your pictures you say, has a jiggle valve, also the lower disc is smaller than the GTA original stat, It looks very much like a 610 stat with the jiggle valve and smaller disc ......... and temperature rating of 86 degrees.
Can you put my mind at rest please.