We are trying to fix a running hot water faucet in an old apartment. We got the hot water turned off (with much difficulty) behind the tub, but no matter what we do (wrench, WD40, trying to scrape away the residue of years), we can not get the faucet to loosen up to replace the washer or the whole faucet.

Plan B was to also turn off the cold water behind the tub, remove the entire unit and replace it, but the cold water turnoff is so "frozen" together that it won't turn off.

It's not our property, but (long story we won't bore you with) we need to fix this faucet. Does anyone know any cool tricks for getting these old fixtures to "turn loose" so we can fix them?

Thanks in advance.

Nothing beats heating it up with a torch and quenching it. Many times a torch in a tight place creates other problems. Vibration often works better. Maybe slip a short length of pipe over the stem and hammer on it. You don't want to bend or bust stuff, just stress the corrosion holding the nut from turning. Many light blows are better than heavy ones. It also helps the penetrating oil wick in.