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MG MGB Technical - Thermostat Housing stuck

Hi,
Just got the magb 1969 running after 5 year of rebuilding the body. Cannot get the thermostat housing free from the engine. I've tried lost of penetrating oil, heating and cooling the housing and lots of gentle hammering but it's still stuck to the engine. I'm afraid to hit it too hard incase I crack the housing or snapping one of the studs. Does anyone have any ideas please?

REgards
Derek
D Beardsmore

Derek - A putty knife with the blade sharpened at a 45° or less bevel can be very carefully tapped onto the joint between the housing and head. Work your way around the housing until the entire housing is raised a small amount. From that point carefully working the housing up and back down repeatedly will loosen the rust around the studs. You are probably going to want to replace the studs (or at least remove them so they can be cleaned). If they won't come out with a couple of nuts jammed together at the top of the stud to turn the stud, then try heating the joint between the stud and the head as hot as you can get it with a propane torch (or better and welding torch) then touching the joint with a candle. Let everything cool to ambient temperature and try backing the stud out. Cheers - Dave
David DuBois

David,
Expound on the candle part if you don't mind. Does the wax penetrate the joint and in some way lubricate the threads or what is its purpose? Thanks,
Frank
Frank

Crud and corrosion forms around studs, and the corrosion at least expands to wedge itself between the stud and the housing. The same thing happens on heads (with studs instead of bolts) and front covers like on my V8 - that took a lot of wiggling and penetrating fluid before I could get it off. Why they put one long stud in there when the rest are bolts I have no idea. Heating a stud will expand it and so compress the corrosion, and when the stud cools and contracts a little it is supposed leave a gap to make things easier to remove/undo, which is why heat on its own is the first recourse (or 2nd after penetrating fluid). Candle wax will be very runny on a hot stud and so penetrate, then cool to a more lubricating grease. Although penetrating fluids on their own *should* work if the candle is going to work. Double-nuts on the stud just enough to get the stud turning may also be enough, as long as they *are* being turned and not twisted, as too much of the latter will weaken them if not snap them off. Many years ago I used a combination of Diesel and colloidal oil, in graphite - the former for penetration and the latter for lubrication. Shifting stuck/rusted things is a matter of using progressively more agressive techniques until it comes apart - or snaps off requiring replacement or drilling-out and retapping.
Paul Hunt 2

The melted candle wax is supposedly drawn down along the threads as the joint cools. I have had good results using it where plain penetrating oil has not worked. I suspect that the candle wax on a hot joint woks quicker than just soaking with penetrating oils do and being basically an impatient individual, I have twisted off fewer studs using the hot wax method. Perhaps if the penetrating oil were to be applied to a hot joint it would work as well. Cheers - Dave
David DuBois

This tip is no use to you at this point - but when you refit the housing put some thread sealant on the studs before you screw them in. On my engine they appeared to enter the water jacket itself and putting sealant on meant that next time I wanted to remove them there was no corrosion at all.
Miles Banister


I've got the same problem. Though on my 1980 car I blame it on the filler for the cooling system being incorporated in the housing as much as anything.

Heat etc was totally ineffective; so decided to take a long term approach, made a tubular drill and relieved the housing around the studs to about 50% of the depth to act as a reservoir for penetrating oil. After several months housing and studs are still solid, so may have to resort to trying to split at the joint.

I brought a set of zinc plated studs from Chris at Octarine Services - he also recommends painting them before re-assembly to reduce corrosion.

Vic
V Todman

This thread was discussed between 23/12/2007 and 30/12/2007

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