broken thermostat stud !

[rolando38]

hello

as my thermostat (Otter switch) was not working I decided to change it
when I unscrew the first nut, the stud broke right away



I didn't previously spray WD40 as the apparent part of the stud coming out of the nut was "clean" (see right part of the pic)

but alas the internal part of the stud (see left side of pic) was badly rusted


I have since then generously sprayed WD40 but I'm hesitating to go further and unscrew the 2 remaining ones; better 1 permanetly on thermostat than a permanently leaking radiator

what would you suggest ? any way to replace the stud ? need to weld a new oene ? (I hate welding)

[christopher storey]

Soak all 3 studs in penetrating oil or even better a 50/50 mix of acetone and auto transmission fluid , and keep applying regularly over the next 3 days or so. Then undo , without applying too much force, the other 2 nuts. Apply more penetrant to the broken stud , and preferably some heat with a heat gun, and try and grip the broken off bit with mole grips so that you can unscrew it.

[rolando38]

thanks Chris
will do
I can save the nut , but the stud is gone
the plate on which studs are attached (brass ?) does not come as a spare part at Barrat, although it seems to be separate from the rad itself; should I braze thz broken part of the stud on the plate ? or a new one ?

[christopher storey]

Rolando : I think I have misunderstood your picture . I thought that what you were showing was the temperature transmitter attached to the manifold/thermostat housing. If that were the case , then as far as I know , the studs themselves should go right through the plate and fasten into the top surface of the manifold . Now I look more closely I see that it is in fact the otter switch ( which if I had read your post more closely I would have realised ) so I do apologise for giving misleading advice

I think I would take the whole radiator out and take it to a radiator workshop who will be far better at dealing with this problem on a copper/brass radiator , although my advice on penetrating fluids still stands

[JagWaugh]

Soak the other two fasteners in ATF/Aceton and get them out. If you have the patience you could drill through the centers of the studs, then boil what is left out with a saturated Alum solution. I boiled a broken Otter stud out of the cooling manifold on my S... it too about 7 hours, but I did have a broken bolt extractor stuck in the hole for the first 4 hours until the Alum dissolved enough of it so that I could pull it out with tweezers.

As long as you have a ferrous bit stuck in a non ferrous part, you can always boil the ferrous part out with Alum without ANY damage whatsoever to the non ferrous part.

But it does take a bit of imagination to get the problem area immersed in a bath at a slow rolling boil, not to mention some patience.

Andrew

[rolando38]

Thanks Andrew

if I understand correctly, your proposal of Alum baking is in case I cannot remove the nuts without damaging the studs , right ?
I hope with sufficient ATF/Aceton mixture they will come out

but to "recreate" the mising stud, I might have to hand it over to a rad specialist as suggested by Chris

[JagWaugh]

Rolando,

No, soak them in ATF/Aceton and remove the nuts. Once the nuts and Otter are off, Soak again with ATF/Aceton, try a bit of heat, and vice grips to remove the studs... these may break.

To get the broken steek studs out of the brass, boil in Alum. This will dissolve the steel chemically, without touching the brass/copper/Aluminum. This is an old watchmakers trick - but there I am only dealing with screws less than 2mm dia stuck in rather small brass plates ... the #10 studs will take a bit longer, but they will be dissolved.

Andrew

[rolando38]

OK, got it
I thought the studs were in brass too
Being in steel inserted in brass, if I heat the brass the faulty one should be freed; if not sufficient, i'll try your trick
thanks for helping !

[paulsco]

It is always worth tightening up seized nuts/bolt a little before attempting to remove them; this breaks the seal between the treads and they are far easier to remove.

Paul

[rolando38]

True, good advice !