Hey guys,

First off I would like to start by saying Happy Holidays.

My dad was running his 87 Corvette in the driveway the other day when it sprung a leak. A pretty big leak as a matter of fact. He couldn't figure out where it was leaking from so he gave me a call. I decided to take a look tonight and i can't seem to figure it out either. Added about a 1/2 gallon of antifreeze... ran the car about 10 minutes. Shut it. No leak visible. Did this about 3 more times, still no leak?????? There is some dampness towards the front of the engine on the passenger side below the a/c compressor. The front leaf spring is saturated, but other than that the engine is dry. Any ideas????

DG

Well... A couple of places to look.

1987 Vettes have this so-called oil cooler. I think it's more of an oil heater, but, it has a bunch of hoses that run under the front of the engine, out of the block (think knock sensor boss) into the oil filter housing and back into the block. Or something like that. Regardless, it is a piece of shit design and is prone to multiple leak points.

Check for that.

Or, you have blown the head gasket.

10 minutes isn't enough. Run it all the way hot, until the fan is about to kick on, then shut it off. Then after 5-10 minutes you'll find the leak. This is when system pressure peaks at the 16 psi on the suction side of the system. Hopefully just an oil cooler hose, lower radiator hose, or heater hose leak.

A punctured lower radiator hose will barely even leak when the car is running because the waterpump is drawing the pressure down.

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That's pretty much what I did... 226*F the fans came on. Ran it about a minute more and then shut it. No leak. What can I do to help induce the leak? I am thinking it could be the lower hose... its wet around that area.

DG

All I can suggest to find the leak would be to add dye to the radiator... see where it comes out.

Another option, let it keep running... it's bound to expose the leak at some point. I mean, how long was Dad driving it when it started to leak on him?

Bad radiator cap?

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Interesting you should say that. Just last week I had that issue. The water was blowing by the cap and into the overflow. From the overflow it overflowed across the the air dam and down. Yep , possible. Cheap fix too.

Could just be the lower hose clamp needs tightened up. I've had that happen, when it is just a little loose it seems to leak at peak pressure, as CC explained.

Just pressurize the cooling system with a pressure tester. Some leaks won't reveal themselves until they are under sufficient pressure. With the system pressurized you'll be able to either see or hear the leak(s) and have the engine off. And you can verify the pressure holds steady and no additional leaks are present elsewhere afterwards.

I have found waterpumps that will only leak when you wobble the pulley by hand with the belt off.

When using a pressure tester don't exceed the radiator cap's psi rating to be safe. In this case that's about 16 psi.

If you don't own one places like Advanced Auto, Oreilly, and Autozone rent them with refundable deposits which makes it ideal for seldom use. You can also buy the tools outright. The Autozone unit comes with an adapter to also pressure test the radiator cap itself. I bought my own pressure tester since I find myself using it rather often. Great tool for finding coolant leaks.

Thats what I used to find a water leak I had. Couldnt figure out where it was coming from. With the pressure tester, and the engine being cool, I could stick my hands everywhere to find the leak. Ended up being the metal plate on the back of the water pump that sprung a little hole in it.

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That's one of the great aspects about it. Another is the fact that the motor is off so you can hear any hissing from other small leaks you would not have found otherwise. If the pressure needle does not stay rock steady, you know you're not done and have not found all of the leaks.