Rusty pipe flange. Need to separate

[7018fiend]

I'm trying to redo the pipe on my exhaust for my truck. In order to take only the section off I need welded, there's a flange right after the catalytic converter that I should be able to unbolt. Only problem is it is so rusted that I can't get it to come apart. Any ideas?

[elvis]

Pb blaster or wd40 and let it sit? How fast does it need to come off? Can you heat up some part of it to break it loose?

[backhoe1]

BFH---works every time.

[Helios]

Heat wrench...BFH...hacksaw...O/A torch

[MMW]

If your just talking about the bolts then get new ones & cut off the old ones. If you have already done that & the flanges still won't seperate then you can try heating them with a torch & hitting with a hammer. Also maybe there is a spot you can get a chisel started between the flanges to force them apart.

[7018fiend]

Ok. I think I'm gonna try the chisel since I cut the bolts and it's still attached. I don't really have access to a hot enough torch so thats out the window.

[wrench3047]

If inner pipe is trash denting it inwards will help breaking the rust. Heat from a propane torch would be a big help. Either way wd-40 and tapping it with a hammer will help too. If you spray it before heating it watch you eyebrows.

[Wheelchair]

Kroil

[Rezeppa]

Invest in some Kroil Oil and O&A torch. Do you have an air hammer? cut off a bit or buy a hammer bit and vibrate it off

[mikesystem]

I do lot of custom exhaust work please post what year model motor and ect ect ect i can tell you a easy way to fix it u might not need to worrie about the flange behind the cat post it up and will advise