WD40 is a decent cleaner and short term lubricant, but it is not too good for loosening rusted bolts. It was originally used to repel water on rocket fuel tanks to prevent rust and corrosion. The name stands for water displacement 40th attempt.
PB blaster is designed to be used for rust penetration. It is a catalyst that will dissolve rust, and it does have some lubrication properties. SO, if the bolt is rusted in or corroded in, the PB blaster will do a lot more. It will actually eat the rust and dissolve its way in to the threads where WD40 will just sit on the outside and clean off the loose bits of rust.
There are other chemicals that work to dislodge rust like liquid wrench and some others. I personally have had better luck with PB. Might have to spray it and let it soak, re-applying for several hours or even overnight.

 

I have used a heat gun to heat up old O2 sensors that were stuck to red hot, worked like a charm. I'm sure it would work here too, a more centralized heat unlike a torch.

 

Good info!

The WD thing I (partially) knew the story but knowing the rest is good.

I bought a can of liquid wrench as my local shop didnt have PB so ill give that a go

 

I actually do have a heat gun (somewhere...) - I'll try to give this a try this weekend.

Thanks!

 

If it's on the caliper aka caliper pin and not the caliper bracket bolt, you can take the brake hose off caliper, flip it up, use a air hammer or rivet gun with a flat set in it and drive it out. Had to do that on the rears for my grand prix. I prefer the seamfoam penetrating oil and got best results with it, not cheap. Aerokroil works wonders too, not not cheap. Before using any extractors once it starts rounding use standard socket and beat it on there and try again as last effort. Once you go
the route of extractor if that rounds it out your screwed. Another thing make sure you use a 6 point socket and not 12pt