funny...it is stuck bleeder valve that prompted this post...so got it...heat the valve and not the caliper into which it is screwed...douse it with cold water...and then put a vice grip to it (rounded it several turns ago...)!!
Edl
There are actually two different techniques being talked about right now which is probably confusing at best to you:
1. Thermal expansion
2. Thermal 'shocking'
Thermal expansion is heating up an external piece to expand it away from an internal piece. eg a nut that is tight on a bolt would require you to heat the nut, to expand it from the bolt. Take that bolt and thread it into a housing and it would then be the housing that required heating to help get the bolt back out. In this case, your example would be the wrong way around. Having said this, I don't know how much heat you can safely put into the caliper due to the seals and stuff. They are obviously able to handle braking temps but a torch should run quite a lot hotter than that.
Thermal 'shocking' is putting the entire joint through a very rapid heat cycle. As said above, torching and then dousing with water is an effective way to do this. This rapid expansion and contraction basically shocks the whole joint and helps break the bond between the two pieces. This can also be achieved by hitting the work pieces with a hammer and/or punch. It's amazing how much difference some vibration makes to any tight fitting, whether it's threaded or press fit.
In this case I would go with the heat shocking process. Also, penetrating oil does not usually make much difference on pipe thread fittings anyway. The threads are too tightly engaged for the solvents to break anything down or the lubricants to lubricate anything (if it is pipe thread anyways).
Also, if you have or can borrow a pipe wrench or some Knipex Cobras, I find both work much better than vise-grips.
