Freezing broken bolts

[greydog]

I have two broken head bolts on a 1600 block.
I made a drill jig and have a hole thru the center of each bolt.
Repeated soaking with WD 40 Penetrant have not loosened either bolt.
The engine is still in car so I hate to wave a torch around the engine compartment.
Wondering if anyone has tried freezing a stuck or broken bolt to loosen it. I see CRC has a "freeze spray" product that sounds a combination of penetrating oil and refridgerant.
Or, maybe a few bits of dry ice poked down the hole in the stud.

Anyone had luck with such a scheme?
Dan

[Curtis]

I bought some left hand taps with the thought that maybe I could drill and tap and possibly turn them out that way. I was thinking put a left hand bolt in and then tap on the head to hopefully loosen it. How about putting heat on it with a soldering iron? No flame.

I have yet to have an easy out work.

Since they are head bolts you would probably have to worry about metal shavings.

[autoairman]

try melting some wax on the bolt and let it work down the threads.a sharp rap on center of bolt might work also.both options have worked for me in the past.
just my 2 cents

[C.Costine]

Left hand drill bits have worked like magic for me.

[theunz]

I have had good luck with PB Blaster. Sometimes I have had to just keep drilling the hole bigger and bigger until you're almost touching the threads and then a punch usually makes quick work of it. You have to be very careful using this technique, especially if your hole is not dead center.

[greydog]

Thanks Mike. I'll get some PB Blaster (ran out) and try.
Dan