Thermostat housing

[Unimatrix1066]

I ve just renewed the thermostat as it failed , however after refitting the housing with a new gasket and tightening to the correct torque it leaks nd ideas or experience of this would be welcomed

[philthehill]

There can only be four problems as regards the thermostat housing

1. The gasket surface of the thermostat housing is not flat or the gasket surface has corroded.

2. The gasket surface of the head is not flat or the gasket surface has corroded.

3. The gasket has failed or is incorrect.

4. The hose outlet is corroded and it allows the coolant to leak past the hose.

Check for the above.
If the gasket face of the thermostat housing not flat put a piece of medium wet and dry on a piece of glass and slowly work the gasket housing over the glass to improve the surface, use WD40 to lubricate the wet and dry. A bit more difficult with the head but clean up the gasket face with a piece of medium wet and dry.
Make sure that the hose outlet surface is not corroded and clean up again with wet and dry.
If any of the above are too corroded replacement may be the only option.
Make sure that you clean up all wet and dry paste from the head and thermostat housing before re-assembly and use.

[mogbob]

Phil has cracked the issues for you to look at.
If the surfaces are suspect. you can get away with some form of chemical metal filler.beware of slapping too much on...
otherwise you'll spend ages sanding off.Best remove the thermostat housing from the engine if that is the offending bit.
Its easier to rub it smooth on a flat piece of glass as Phil has suggested.My repair is still watertight after 10 years.

Replacement is the quick fix if there are sufficient pennies left after Christmas, if you don't want the hassle.
Bob

[simmitc]

Did the cover go one square? If it's tight on the studs then it might have jammed at a slight angle, remove and re-fit with new gasket.

[bmcecosse]

Unusual for a thermostat to fail - was it stuck open ? The others have covered the repairs - try to avoid any use of 'gasket goo'......

[beero]

Did you nenew the studs? If so you need to seal the threads where they screw in the head with some hylomar or similar as you can get water seeping up the threads. I had this, but can't remember whether it was on my Minor or MGB.

[Unimatrix1066]

I will have a look when I get a chance it's the end of the tax year so busy, the thermostat failed as it was getting cold driving at the weekends

[bmcecosse]

And you found it lying open when you took the cover off? I ask just because I have never seen one failed open !

[Declan_Burns]

Never had one fail open on the Moggy but here's a photo of a failed open MG TD thermostat-the black one.
Regards
Declan[frame][/frame]

[bmcecosse]

That's an odd one! Is there anything trapped in it ?

[Declan_Burns]

No Roy,
Just seized solid. Those thermostats are sealed units with an integrated sleeve that opens and closes the bypass.
Regards
Declan[frame][/frame]

[bmcecosse]

Crikey....so what do you do now....I doubt these are 'off the shelf' items.... ? Can you clean out the old stat and somehow modify the housing to take a modern stat?

[Declan_Burns]

They are readily available and some of the repros are fitted with a replaceable modern thermostat with a hole instead of the original sleeve. Expensive though! I was lucky to pick up an original-(the maroon coloured one) locally on fleabay.
Regards
Declan

[bmcecosse]

Lucky indeed...so now you can modify the original one !