diesel thermostat housing leak

[ewenmaclean]

Hello,

have searched but not found a similar problem - apologies if this has been discussed lots before.

I've replaced the thermostat and water pump on my tdi - much the same as for any other diesel. The problem I have is a slow leak coming from the thermostat cover - I replaced the o-ring and everything's in the right way.

I don't want to put hylomar all over it as it'll break off and end up in the cooling system - no sure if a new cover would solve the problem. Does anyone have any tips on how to stop this slow leak? Any advice or help much appreciated.

Ewen

[Oldiebut goodie]

I may have the answer or I may not - I have just had exactly the same problem. (After a nice refreshment of the anti-freeze of course)
Firstly the new o-ring that was supposed to fit was slightly loose on the flange - different o-ring sorted that.... but still a weepage was evident.
Next, closer examination of the thermostat housing revealed that the flange had become oval..... new housing used and problem solved.
It appears that the plastic can become deformed with the heat thus creating a weakness in the o-rings seal. I am reasonably confident that you have exactly the same problem.

[ewenmaclean]

Thanks a lot for the reply - just what I wanted to hear! The old cover doesn't sit perfectly flat on the water pump housing so I suspect deformation, but wasn't sure - so good to know you suspect the same. First time I've had this problem - will replace the cover and report back - will also get an oring just in case....

Thanks again

[pauly8888]

My thermostat housing was also deformed. Not obvious at first sight, but when placed on a flat surface it 'wobbled' quite a bit! The 'o' ring was squashed almost flat too.

[ewenmaclean]

thanks - mine's got that wobble - good to get confidence that's what the problem is... I'll report back when new one's fitted to confirm that is the problem..

Ewen

[Oldiebut goodie]

If it has gone oval rather than just wobbly it will affect it more as you will have the o-ring not making a complete seal inside the circular housing. The ovality on mine was over 4mm so there was no chance of a good seal.

[ewenmaclean]

All sorted,

it had indeed gone oval - will try and post a pic soon.

Thanks Oldie and Pauly for the info and help

Ewen

[weldore]

its a bit of a common fault with this type pf engine..even the petrol ones.my old agg had done the same..a new one is better than messing around with sealant