While removing the thermostat housing and sandwich plate on a stored core engine, I was surprised how easily one of the bolts broke.
The bolt has broken below the head surface.

Is helicoil a viable fix for this problem once the bolt remnants are removed through drilling or milling?

Is the bolt of such hard material that its removal requires super hard material in the drill bit or end mill?

I have installed helicoils in aluminum very easily. How easy is it to install them in cast iron? Do you use different helicoil kits for cast iron?

Whomever installed the bolts last time obviously didn't use any type of anti-seize or otherwise this problem could have been prevented. Just goes to show that we should all use ant-seize in all blind holes where
corrosion is possible(like rear subframe trunnion bolt holes in the shell).

Other places where anti-seize can be used to prevent seized bolts are: caliper bolts, bleeder screws, plumbing fitting holes in calipers and block.
If this had been an expensive prepared head(Longman, Swiftune, Calver, MED,etc.), broken thermostat bolts could be a major teardrop that could easily have been prevented with anti-seize.

Carpe diem(seize the day). Use anti-seize or be seized. Don't have a seizure, use antiseize.

These studs or bolts are only grade 5, nothing special.
I mark and drill them ON CENTRE, then screw a 5/16/UNC tap in to remove the remnants.
It's not too hard, easier than removing S/S studs from alloy outboard motors...
I like using bolts, with Loctite #3 gasket cement on the threads. it keeps the water out...
Bolts are better because they don't seize solid in the alloy thermo housing like studs do.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

A good way to remove broken bolts/studs that i have used for many years is to weld a nut on to the top of the broken part with a mig welder. You pool the weld up inside the nut untill flush with the top and while its all still hot use a spanner to remove the stud. Works very well on broken head studs, exhaust studs & thermostat housing bolts/studs.

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Have a Nice Day.
If already having a nice day please disregard.

thanks for the tips !

Same method, same kits, no problem to fit.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Now thats a nice solution! Beats the hell out of drilling and busting ezyouts!

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Ezyouts are a waste of time in this application. If the stud is so tight that it broke when undoing, no way will an ezyout remove it. It'll probably break first, then you have a REAL problem, as they are hard as buggery.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I Love Copper Coat

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

probably Copaslip by a different name.

Caltex call it Kopr Kote if you see it for sale in a servo. Magic stuff

[quote="drmini in aust"]These studs or bolts are only grade 5,
It's not too hard, easier than removing S/S studs from alloy outboard motorsquote]

Or jet skiis which is what i spent my weekend doing.

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