I'm not sure which ones are leaking yet, but from what I've read searching this too-common problem, I want to try using those sealers you dump into the radiator before tearing into the motor again. Someone suggested pellets that you crush and dump into the cooling system, GM part # 3634621. I figure if GM uses it, it must be the best stuff.

My question is, what's the exact procedure to use this stuff properly. Do you first drain the coolant, fill it with water, dump in the pellets, then circulate the fluid and drain it again?

Who's used a sealer like this successfully and how much do the GM pellets cost?