[Vwdiesel] Broken headbolt

[Roger Brown]

Val Christian wrote:
> On the headbolt.  This should be real easy.  With an oxyacetylene torch,
> heat the bolt to a dull cherry, right down to the casting.  Don't heat the
> block (or you may have more serious problems!).  The idea is to expand the
> bolt, crushing the rust matrix, which is helping to hold it in place.
> Rust is not strong, and the heat is enough to compress it, breaking up
> the structure.  Then, as it cools, dribble some penetrant on it (to help
> lube all those crushed rust particles), and turn the shaft with a
> vicegrip, stud remover, or whatever.  You can wait until everything is
> cold, or you can start trying to turn things while it's getting cooler
> (500F?).
>
> Castings (the block), don't take well to heating and you could end up
> with irrepairable damage.
>
> FWIW, every time when I have stuck nuts, bolts, etc. I always try penetrant,
> impact, and messing with it for a long time.  The torch is nearby, but I
> somehow hate to use it, because that usually means I replace the fastener.
> I'm learning slowly that the best approach is to transition to the torch
> sooner than I do.  The other day I beat on brake rotors for 5 minutes.
> My son, who is smarter than I, handed me the torch.  Both rotors got free
> from their hubs before the front wheel bearings even got too hot to touch.
>
> Heat can help you damage things less, and get the job done faster.
> Just do so carefully.

Welding a nut on the top of the broken bolt will also heat it up, I've used this on other fasteners that were broken or stripped
and the heat of welding can loosen them right up, too.  Had a drain plug once that was in very tight and the head was stripped,
welded on a short bolt w/ head and it hardly took any force on the wrench to back it out. Another trick is to heat up the bolt
enough to melt paraffin wax and let some of that wick down along the threads.  It seems to penetrate the rust matrix very well
and makes a good lubricant for removing the stuck bolt.

--
    Roger