bolt breaking woes

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klerk

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so i went to both replace the thermostat and water pump (upgraded to 9 blade fan variety) on my fathers engine transplant (engine still on stand) and broke no less than 3 bolts. 2 on the thermostat housing and one of the water pump studs. in researching the best way to remove said metal my plan is to first try the reverse drill bit method...followed by the last ditch "easy out" scenario. final course will be to retap and helicoil. anyone have any advice? i read somewhere to heat up the metal (torch) a bit before my efforts. i'm hoping the fragile bolts are not a sign my donor engine was mistreated in its former life. anyone?

TIA
 
Those bolts/studs are probably the most common to break. 6mm is a small section, and a little corrosion can really lock them in.

Definitely apply some heat before you go at them with the back-out bit. It may take some time, but the odds of you prevailing over the bolts are good.
 
And when reinstalling the new bolts be sure to use some anti-sieze on the threads. It will save a lot of heart ache when you have to replace those parts again thirty years from now.
 
thanks guys. so can i pick up some new bolts from my local parts store...or is there any wisdom to ordering from a bmw supplier?
 
I have had good luck using white thread sealer so the bolts don't rust.
 
New bolts

I think your attack sequence is good. Save the easy-out for last. I have broken several of them, they are very brittle. A reverse handed drill bit only just smaller than the bolt is your best bet. First drill a small pilot hole, then the larger left-hand drill. The heat and vibration may well take it out.

Heat works because aluminum expands more quickly than steel when both are heated.

Wherever you source new bolts, make sure they are the same hardness grade. Low strength soft bolts will surely break next time too. They don't have to be from BMW, just make sure the hardness is up to snuff. Know how to read that from the bolt head markings, don't you?

On my second water pump job I was really happy that the antisieze from the first job had worked - out they came with no muss no fuss.
 
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