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Thermostat Housing Stud Threads

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#1 sam138


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Posted 24 May 2019 - 06:30 AM

Just wondering if someone can help please, I’ve fitted up a new thermostat on a new cylinder head but it keeps leaking through one of the stud it’s self.

I’m finding the stud very tight to fit in and was going to clean out the threads and maybe try some ptfe on the thread ? Or some Loctite.

Any ideas please ?

Edited by sam138, 24 May 2019 - 06:31 AM.

#2 Curley


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Posted 24 May 2019 - 08:47 AM

I've never seen them leak via the stub hole before, I suspect it's the thermostat housing gasket that's weeping. Make sure both the mating surfaces are clean and reasonably flat. If needed buy a new gasket.


Running a 5/16 UNC bottom tap through the holes in the head & re-assemble with a new gasket before even considering PTFE or loctite

#3 nicklouse


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Posted 24 May 2019 - 09:04 AM

leaks up the studs is usually damage. either to the gasket, head or housing.


pull it and check the gasket and the housing.

#4 Ethel


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Posted 24 May 2019 - 09:06 AM

If the hole goes through to the water jacket they can leak up the threads. Loctite would be my preferred fix.

#5 Readers14


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Posted 24 May 2019 - 03:34 PM

Yeah, Loctite thread sealant fixed mine.

#6 Moke Spider

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Posted 24 May 2019 - 07:55 PM

It maybe leaking up the thread, but more usually, I find it's across the gasket here. There's only a small profile of gasket material between the T'stat and the stud and being what it is, that mating faces are seldom ideal. I find some RTV sealant usually works, but you'll also want to be sure the faces of the head and housing and flat and clean.

#7 sam138


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Posted 24 May 2019 - 08:33 PM

Thanks for the reply’s, I’ve ordered this Tap set and will run these through each thread with a new gasket and see how it fairs.

#8 DeadSquare


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Posted 24 May 2019 - 09:50 PM

The three holes in minispares thermostat housings are almost 3/8" and get very close to the edge of the thermostat.


I have found that, having inserted the thermostat, I need to put a wodge of sealant on top of the gasket, round the bottom of the studs before fitting the housing and squidging sealant up the studs.

#9 RooBoonix


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Posted 25 May 2019 - 06:39 AM

I have billet thermostat housing and sandwich plate, new gaskets and fibre washers under the bolts. Doesn't leak a drip

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