This is a reposted subject, but I just wanted to add my name to the list of people who have used stop leak to fix a water seal that is leaking into the rotor. I bought a 86 GXL the other day because the car would start, and when it did, it would puff white smoke for a minute. The dealers mechanics didn't know how to fix it, and the local Mazda place doesn't work on them because there aren't enough RX-7s around here. I got the car from them for mad cheap cause I told them I could fix it and they had it for a while and nobody would buy it cause nobody can fix it. I drained the coolant, put so stop leak in there (3/4 of the bottle) and started it up and slowly added coolant. I shut it off after before it got too hot, added some more coolant until the add coolant light stay off when I turned the key forward, then I started it and let it run until it got up to normal temp. I shut it down and let it sit 24 hours, and now it starts without having to be unflooded first.