Ok is I have some history with this history on two different MK3. A year ago I've noticed overcooling - the coolant temperature went down whenever I was driving at highway speeds and/or on a cool day and/or with the air conditioning on. So I've replaced the thermostat with an cheap Chinese one which fixed the problem completely...for about 6 months. I've attached the photo of the two and you can see the old one was broken where the plastic encapsulates the rubber seal.

So yesterday I bought another thermostat, this time from Europe (made by Topran) and replaced it again but this time it did not fix the problem at all. The old thermostat that I took out did have some melted plastic but it still seems operational so I have no idea where to look for the problem now

 

And this is the thermostat I took out yesterday. It is the same one as the top one in the picture attached in my first post above

Edited 13 March, 20233 yr by PIXIP

Solved! I took the housing out and the thermostat was not in its place. One of the plastic brackets broke off (the one on the right in the second picture)

Hi,

 

Thanks for making this post. My car overheated and thermostat is toast and maybe other things.

 

Did you get away with reinserting the thermostat or did you get a whole new housing.

 

To be honest the "plastic bracket" you show as broken off on yours looks like it was never existent on mine anyway. But both the other (I'll call them protrusions) on mine are completely snapped off too or maybe were never there if you look at the photo.

 

 

 

In the above image the centre two rings form a cup that the thermostat will actually sit in but I'm wondering if it's enough on its own without the protrusions. I'm wondering if the protrusions are just for ease of assembly or maybe they were never there on this engine.

 

The pictures below I've put the broken base of the old thermostat in place (green rings) and indicated how the protrusions (red rings) would hold the thermostat directly if they were there.

 

 

Anybody know of a decent brand to purchase a copy thermostat housing off Autodoc or similar.

 

I have a new Contitech Thermostat and end piece and an OEM stat and Topran end piece too. Yes the end piece did have a hole straight through it.

 

Question is though: what other bits could be missing in the thermostat housing.

Edited 3 December, 20241 yr by cosaw

Very quick update. I've found a used thermostat housing in very good condition. So those plastic "protrusions" on the thermostat housing are definitely supposed to be there (on this version at least). And they do a good job of holding the thermostat in place while it's being reassembled. The third picture down in the thread does show it best. And I'll also say that the third protrusion (which is shorter and attached to the sidewall of the the thermostat) does seem like it's supposed to be short as I've seen it the same in 3 thermostat housings now one of which was a very cheap non-oem version I bought.

No offence to the original poster is meant but I would say that the situation in picture five in the thread is an installation error which those protrusions are actually there to try and prevent (at least in part and to some degree - they will also keep it aligned when the thermostat opens and all the pressure is on the end pin of the thermostat). I've tried - and putting the housing back together on my broken housing (without the protrusions) is a lot more tricky. Just my thoughts on it - not saying I'm 100% correct and it would certainly seem that the failed (non-oem) thermostats in the original post were probably pretty poor.

Edited 6 March, 20251 yr by cosaw