21 replies to this topic

[BenSwan]

Are all thermostat housing bolt threads removable? I attempted to remove them from this 12g940 with a blow torch and mole grips but they don't seem to want to move. The housing broke in the process which I read that's common so not an issue replacing it. The threads where already stripped beforehand with the nuts missing.

Would I be best repairing the existing threads? Or will they come out if I cut them down, weld a nut and use a breaker bar? Or any other suggestion?

Thanks all

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[nicklouse]

First off of those are studs. Bolts have also been used on some later cars.

 

yes they are all removable.

 

soaking with a good release agent (not WD40) for some time in advance helps.

 

but for the really stuck ones you need to break out the Oxy and get it cherry red.

 

bits that break off don’t make the head scrap as they can be fixed by brazing and drilling and re taping. 

[Magneto]

Propane will never do it, like Nick says you need Oxy acetylene to get it hot enough - only heat the stud, not the head itself. 

 

I have had a few over the years that just wouldn't come out with out breaking out the torch, but on these - maybe just clean up the threads and use them as they are? 

[BenSwan]

Thanks both.

Is there a recommended release agent to use?

I was considering renewing the threads with a tap and die but is that cheating? Haha.

[cal844]

I have used Plus Gas with good success

[greenwheels]

in cases like this I tear off a piece of rag about one inch wide, wrap it around the base of the stud and soak it in a good penetrating oil (not WD40 - that's a water dispersant fluid), and leave it overnight to soak. Good luck

[Midas Mk1]

Plus gas or pb blaster (even better), honestly it works.

[Maccmike8]

Another vote for plus gas.

[gazza82]

I've had reasonable success with Screwfix penetrating fluid when stripping down my Austin ...

[Magneto]

These studs don't look bad in the pic (it's a little blurry tho) so yes, I would run a die down them and call it good. It's only holding the thermostat housing on, with a good proper gasket it doesn't need that much tension to seal it up.

[jaysmini1983]

this stuff works really well

 

https://www.ebay.co....O4aAuGxEALw_wcB

[T.Harper]

AC Dodd has put a video out on just the issue:

 

 

[T.Harper]

Propane will never do it, like Nick says you need Oxy acetylene to get it hot enough - only heat the stud, not the head itself. 

 

I have had a few over the years that just wouldn't come out with out breaking out the torch, but on these - maybe just clean up the threads and use them as they are? 

I think you mean heat the head around the stud?  Heating stud will just make it expand in the thread.

[Johnmar]

 

Propane will never do it, like Nick says you need Oxy acetylene to get it hot enough - only heat the stud, not the head itself. 

 

I have had a few over the years that just wouldn't come out with out breaking out the torch, but on these - maybe just clean up the threads and use them as they are? 

I think you mean heat the head around the stud?  Heating stud will just make it expand in the thread.

 

what would expand if you just heat the head? The material arround the stud, so that will tighten aswell.

If you heat up the stud, it will expand in the thread and that is what you want:

To my understanding: one heats up a part to break the holding force of the corrosion. So if you heat up a bolt, it will try to expand, and doing so will forcing the corrosion to break (hopefully). I would heat up a bolt and then see if it comes loose. I would not heat up the head if possible to prevent any warping of misforming that coudl lead to a gasket not sealing (very slim change, but why take the change here if one had the choice).

If heating up the bolt does not help, one can always try to step it up and heat the surrounding head material and try then.

I

[T.Harper]

 

 

Propane will never do it, like Nick says you need Oxy acetylene to get it hot enough - only heat the stud, not the head itself. 

 

I have had a few over the years that just wouldn't come out with out breaking out the torch, but on these - maybe just clean up the threads and use them as they are? 

I think you mean heat the head around the stud?  Heating stud will just make it expand in the thread.

 

what would expand if you just heat the head? The material arround the stud, so that will tighten aswell.

If you heat up the stud, it will expand in the thread and that is what you want:

To my understanding: one heats up a part to break the holding force of the corrosion. So if you heat up a bolt, it will try to expand, and doing so will forcing the corrosion to break (hopefully). I would heat up a bolt and then see if it comes loose. I would not heat up the head if possible to prevent any warping of misforming that coudl lead to a gasket not sealing (very slim change, but why take the change here if one had the choice).

If heating up the bolt does not help, one can always try to step it up and heat the surrounding head material and try then.

I

 

Convention is the latter - i.e. get the hole to expand around the stud as much as possible.