Changed my thermostat today.  Brought a genuine thermostat and O ring from TL Darby VW. 

Took me about an hour to sort it all out.  Old thermostat out.  New one in and then new O Ring in place.  Fitted the housing and bolted it up tight.

Then the nightmare.  Starts the engine up and there is coolant coming from somewhere!   Thought it was just excess dripping from the engine so drove a little while.  Then coolant light came on!  Pulled up and it was dripping consistently.  I felt around the thermostat housing and it was weeping from the bottom of the housing! 

So I took it off.  Repositioned thermostat and put O Ring back on again.  Thought I would try tightening bottom bolt before top bolt this time.  Both hand tight.

Damn thing leaking again!!!

So now I`m stumped as to what the hell is going on.  I have looked at the housing and there are no cracks or anything obvious and the O ring looks in good condition.

 

Anyone know what might be causing the weep from the bottom of the thermostat housing.  Anyone had this problem before??  A simple hours job has turned into a nightmare.  My dad had a look and he reckons the housing might be out of shape or distorted because of previous over tightening possibly.  I don`t know.

:(

 

Sam

Stupid question. but you did make sure the old O ring was removed didn't you?

Thermostat housings are known to crack, you haven't over tightened it have you?

Yes the old O ring was removed.  I did it hand tight.  But I didn`t go crazy with it.  I should have really searched first because I noticed on Briskoda someone else had a similar problem and he ended up using gasket sealer on the housing to seal it.  I`m wondering whether I might have to do the same...

I`ve looked all over the housing and it looks in real good condition with no cracks or any obvious signs of damage.

it could be that each time you put it on the o ring slips out of place and when you say you have checked the housing are you checking the engine side or pipe side as either could be cracked just a idea/suggestion

O ring not in place properly is my guess

Have you cleaned the surface engine side I had a drip wen I did mine there was a bit of crap causing the surface to not sit quite right give it all a good clean

tbh I haven't cleaned the engine side. 

You need to make sure all surfaces are clean, the O ring is positioned correctly, and you tighten it evenly. I can't remember the last time I done a thermostat on one of these, but from memory the thermostat housing is plastic isn't it? If it is, it could be distorted. Seen this problem with many plastic housings. It might be worth seeing how much a new one is. Shouldn't be too dear at a guess?

I think they are about a fiver at ecp if it helps

Usually when thermostat is changed, housing is also changed because it can deform.  

Sorted ????

Used fine steel wool to clean down the engine side and put some lithium grease on the O ring and all is fine now!

Weird thing is genuine thermostat and my temp still only gets to 70.  Must be CTS I'm guessing now?

And that's after a run? Is the stat the right was around, no trapped air in the system?

Edited 1 January, 201412 yr by Liverpool-Lad

I fit it so the spring side was facing towards the engine.

I didn't take it for a run, I let it idle on the drive.

Give it a good run m8 and see if its still the same after that.

As above

Take it for half hour run try get on a long straight road stick to 60 if it drops below 90 then replace cts

It never got to 90, the max it got was a touch below 80, then it dropped down to 70 quite quickly, then it tried to edge over 70.

Cts needs changing

I wish I knew this before I went through the nightmare of the thermostat lol, oh well.