K series thermostat leak

[cj247]

Ever since new my K series has leaked coolant from where the thermostat housing fits into the water pump housing. O rings have been changed multiple times, thermostat housing changed & even sourced non Rover O ring as the OEM part is a loose fit.

 

If I drive the car more than once a week the leak is minimal on the garage floor & it doesn't leak when using the car. Any suggestions, other than drive the car more. Tempted to use silicone plumbing sealant as next step but wary of this getting into the engine & blocking coolant ways.

[Stationary M25 Traveller]

Have you got up close and looked at the bore where the thermostat pushes in to the engine ? Is it scratched ?

 

Assume you have fitted the retaining bolt that holds the diptube and thermostat housing to the side if the engine. If that is missing, it could cause problems.

 

Maybe the leak is from the water pump, and it just appears to be from the area of the thermostat. Easy enough to change .... and they do fail.

 

Are your hoses and hose clamps in good condition and done up tight ..... use a socket, not a screwdriver.

[Stationary M25 Traveller]

PS ...... don't consider using silicone sealant

[c7trp]

I've had a similar problem a couple of years ago.

 

In the end I fixed it by getting an o-ring of the same internal diameter but with a slightly thicker (larger diameter) rubber bit. This makes the overall diameter slightly larger and this improved the seal on mine.

 

I took the original o-ring to local bearing/engineers supply place and they helped measure and select a replacement. Cost was about 10p I think! I *might* have the size I used if that helps

 

Be careful fitting the housing into the water pump, as the o-ring may want to roll out of its grove. I used silicone lube and it went in OK.

 

You have checked the hole in the water pump is clean, circular, not scuffed, scratched or damaged?

 

 

[Steve-B]

Been there, done that, worked a treat

 

Quoting c7trp: 

I've had a similar problem a couple of 12 ago.

In the end I fixed it by getting an o-ring of the same internal diameter but with a slightly thicker (larger diameter) rubber bit. This makes the overall diameter slightly larger and this improved the seal on mine.

[cj247]

Thanks for all the suggestions.

 

It is definitely leaking from where the thermostat housing pushes into the waterpump, bolt is done up, bore in waterpump is not scratched & no obvious reason why it should leak, new hoses with all fastenings done up tight. Have fitted slightly oversized nitrile O ring using silicone lubricant. In short everything suggested.

 

I guess the next step, which is a bit radical given the engine has only done 4,500 miles, is to replace the waterpump housing but before I do that I'll try another O ring (that will be 5).