Hello all,

I have an 86 IROC Z28 with an 87 350 installed, with tpi. It's my son's car. While he was driving, the car overheated due to a faulty fan relay, which has since been replaced. Since the car overheated, it has been leaking from about the rear part of the engine, about the middle. Basically around the flywheel. The car only leaks when the car is first started after being parked over night, or after the car has been driven but after it has cooled off. Once warm, there is no leak.

I suspected it was the intake gasket on the passenger side, so I pulled everything off and replaced all the gaskets and replaced. After installation, I started the car and it immediately leaked again. After the car warmed up, no leak.

I am now suspecting a freeze plug is the cause of the leak, from up behind the flywheel, but cannot see to make sure. I did verify that it is not leaking from the heater core or the hoses leading to the heater core. I was able to check those with a mirror.

So, if anyone has any suggestions I would greatly appreciate it. I just didn't want to have to pull the engine if it's not the freeze plugs.

Thanks guys,

Pat

 

You can pull out your thermostat, then hook up a cooling system pressure tester to your rad. This way you can pressurize the whole system, and not just the rad.
Then get the car up in the air (jack it up), and lie underneath, oh, have your raincoat on Then get someone to hook up the tester, and pump up the pressure to ~15psi. You'll be able to watch it leak and pinpoint it easily.

#2 - or you can spray down the car and get it nice and clean, then add some dye to your cooling system, then fire it up and let it leak, then peek under and find that dye. I think this is more annoying though.

 

You dont have to pull the thermostat to pressurize the block, besides their being a small bypass hole in the t-stat you still have the lower rad hose

It definately could be a freeze plug or it could be something not so good, like a warped head or cracked block.

Ill throw in a vote for the dye, give that a shot. You should be able to pinpoint exactly where its coming from.

 

Thanks guys for the suggestions and replies! I'm not sure if it's the head or not. The exhaust isn't indicative of water getting into the exhaust and there is plenty of power and the engine idles just fine, nice steady idle. Fantastic throttle response and no loss of power. I haven't taken a compression test as that is pretty much impossible while the engine is installed! :-) I was also able to use an inspection mirror to see the back side of both heads and could not see any indication of a leak.

I believe I will try the dye and see how that goes and see if I can spot it any further. I don't know why I didn't think of the dye a bit sooner. I may have to also try the pressurization tactic and hopefully that too will help shed light on the situation.

Thanks again guys for the suggestions and I will repost my findings. It may be a few days possibly even a couple weeks, but I will definitely get a posting here of the outcome.

Thanks,

Pat