Hi guys,

I'm in a real bind. I've got a 1996 Vortech Supercharged Z28 M6 with 46k. I've had the car for a little over a year now, right after I bought it the car was getting hot and losing coolant. There was no visible leak, so we changed out the radiator cap. It seemed to fix the problem for a short period of time and then it came back. Took it too a friends shop, he pressure tested the cooling system, found no leaks, held pressure good. Said that the radiator had some debris that was causing the overheating but couldn't explain the coolant loss. I'm not gaining oil and oil viscosity feels good. We changed the cap again and it again seemed to fix the problem.

Two months later...

Driving home from school, car started to overheat so I pulled over. The radiator sounded like it was boiling over. My dad came out and looked at the car and filled the radiator with coolant. We bled the system as best as we could on the side of the road. Started the car up with the radiator cap off and it was pushing the coolant right out of the top of the radiator. We put a pressure tester on it and it was dumping fluid out of the front of the block. We instantly assumed it was a blown head gasket.

We pulled everything off the front of the motor including the supercharger (except the water pump), so we could get a better look at it. We put the radiator back in and pressure tested it, fluid and air is gushing from between the water pump and block on the driver side (Getting wet on the passenger side).

My question is, with this bad of a leak on the water pump, can that cause the gushing that we had coming out of the radiator?

Thanks for any input! We just don't want to rip this thing apart if we don't have to, or put a new water pump on and find out its still a head gasket.

 

First - these cars are tricky to bleed off all the air out of the system and it takes a few tries to get it all or they overheat - I assume you did all that, but it is hard to do on the side of the road when it is all hot. It needs to cool down, then do it. Since water pump gaskets and seals are cheap, you might want to try fixing that before pulling it all apart, since that is a big job. Only thing is that if the water pump leak was at fault, wouldn't you have noticed the big leak before? Also check the freeze plugs.

But it also sounds like a head gasket to me - pressurizing the cooling system, but check the water pump first since it is easier and would have to come off anyway. It might be both. If they overheat a couple times that can happen. The head gaskets can also seem to seal back up for a while after overheating and cooling back down, so be wary of it. You should take a look at the #1 cyl spark plug and see what it looks like. If it is too clean, or it is wet, you probably need a head gasket. If it looks OK, check #7.You might want to also check the oil for antifreeze - see if it is milky looking and off color. All signs of a head gasket problem.

I hope you don't have anything else wrong, but these engines, if they have stock pistons and a blower usually break the piston ring lands after a while, and you can tell that when you take the oil filler cap off and it puffs smoke out of the hole. It might also crank unevenly when you go to start it - you can tell if it varies cranking speed that one cylinder isn't making the same compression as the others. It sill still run like crazy at higher rpms but worse at slow or idle. But if it is puffing and doing like I described, it needs a rebuild.

Let us know what you find.