3 replies to this topic

[tarris850]

'79 City 850

Tried to change the thermostat at the weekend and got very annoyed!

I managed to get all the nuts off without a problem, everything has been removed so in theory the housing should just lift off. it almost seems as though its been welded on!

I can only find threads on stuck nuts and snapped bolts. Am i missing something or it just being stubborn?

Any help appreciated :)

[samsfern]

Unwind the studs out the head, be careful and dont force them if they dont want to go though, last thing you want to do is snap them, failing that, try a bit of heat (with a blowtorch) on the thermostat housing, and gentle use of a hammer, with a bit of wood to soften the blow.

[dklawson]

Consider yourself fortunate that you did not find yourself reading those threads for how to remove broken studs. Having the housing stuck to the studs is probably equally as common as having the broken studs but no one bothers to talk about it because dealing with the broken studs is so much worse.

There are several possibilities to remove the housing. There are quick destructive ways and more patient ways. Which you pursue depends on your schedule and budget.
To quickly remove the housing, find a replacement (first) then use a hammer to shatter the one that is stuck on the car. Not glamorous and rather crude but effective.
To get your original housing off, soak the area where the studs pass through the housing using penetrating oil (not WD-40, penetrating oil). You can apply heat to the housing using a torch and then quench the area where the studs pass through with more penetrating oil. Once wet with the oil and a few temperature cycles, tap the housing GENTLY with a hammer focusing your blows at the thick sections around the studs (sideways). Then apply more oil and wait. The next day, use a sharp, thin, putty knife as a wedge and drive it into the joint between the head and housing. With GENTLE prying and more gentle hammer blows you should be able to get it off. Whatever you do, if you want to use the housing again, do NOT pry on the hose nipple as it will simply crack apart.

[tiger99]

All the above is good advice. I would only add that to get the studs out, try turning them both ways, i.e. looser and tighter, back and forwards gently, until they loosen. Doesn't always work, but often does.

I strongly recommend filling the holes in the housing with anti-sieze compound, copper grease or at a pinch ordinary grease, before refitting it. As you will have seen or guessed, water tends to accumulate in the space around the stud, causing oxidation, and both aluminium and iron oxides take up more space than the original metals, which is why it jams tight. Put some gasket compound on the stud threads too, as they do tend to leak, mostly being drilled right through the head into the water space. The less water that gets into the stud area in future, the better.