I've got a 87 IROC 5.7 TPI. My coolant level in the reservoir is slowly going down. I had a leaky water pump and replaced it, but I'm still seeing the level drop. No puddles under the car. No obvious signs of leaks. I've checked the oil for coolant and it's just plain old motor oil. No bubbles or different odor. Could it just be air in the system from replacing the water pump that's working it's way out? I drained the radiator and replaced the hoses while I was at it. Car isn't overheating at all. Runs great. Any ideas?

Steve

 

Welcome to the club. I have the same issue I can't seem to find the leak.

 

same problem in my 80 buick. lol I know its not a third gen but I was hoping I could get some help on this one. Anyone figure it out yet? I got a couple ideas. maybe old radiator cap, or a leaky overflow tank? havent checked these yet. Also, and this is something I have only heard about once, it was called a "vortec crack" i believe. don't quote me on this, but what I think happens is the head itself cracks somehow, and the coolant hits the exhaust and evaporates. I dont know if its only on vortec heads, or if any heads can do this. maybe something to look into.