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If you see no visible leak and it is losing coolant, you may have a blown head gasket. Serious engine damage will occur if it is not repaired ASAP.


The previous answer is exactly correct. This happened to me on my Grand Prix and I had to replace the entire engine because they couldn't find the problem in time. This will continue to get worse and worse until it finally overheats the engine from the compression leaking into the radiator and the coolant will leak into the oil and the engine will seize up. Get it fixed now!


I just want to add, that I had a 97 Firebird Formula that would leak anti-freeze, but nobody could find leak, including me. It took a dealership 2 days to discover that the water pump had an intermittent leak and would leak out of weep hole in casting, had to be parked with pump rotated to just the right spot to see it leak. They had never seen that before. Probably head gasket, but this might help someone with similar problem.


Park in on a steep incline. Nose up. I had a leak, but it collected in the suspension. It only dripped when parked on an incline.

Tom McD


Had that problem on a 97 Grand Prix. Turned out it was the water pump. The weep hole leaked onto the hot engine and would evaporate all evidence. It would not leak when parked and cooling system was not under pressure. Happened to see a little discoloration directly under pump, decided that must be it and replaced the water pump - problem was fixed.


I had a leak like this and it turned out to be the lower intake to head gasket. I have spoke to several mechanics in my area and this seems to be a common problem. The plastic ring that holds the rubber seal in place in the gasket deteriorates and allows the seal to collapse. I had an internal coolant leak for almost a month before my engine hydraulic locked (luckily while it was parked and not being driven). Changing the gasket is not incredibly difficult if you have had previous experience with working on engines. Everything is fairly accessible, but the upper plenum (black plastic portion of the intake manifold) must be separated from the lower plenum (aluminum piece). There are two bolts hidden underneath it and it cannot be removed as a whole. One thing to be careful for is not to over torque the upper plenum (black plastic upper portion of the intake) when you reinstall it, it can easily crack and lead to more coolant leaks.

I have a 1995 Grand Prix SE and this one is right on. The lower intake gaskets are plastic and junk. Make sure you have put on (or if doing yourself) metal gaskets or you will regret it. I did my own and she runs great. The metal ones are a little more $ but will last. Make sure you flush system a couple of times depending on what the oil looks like coming out of the pan and in valve train.

I have an 06 grand prix that was losing water. Only water dripping was from evaporator drain which turned out to be hot water coming from leaking heater core. Nothing leaked into the carpet area just ran out the drain.
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โˆ™ 2013-08-13 17:22:41
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Q: How do you fix a coolant system leak in a 1998 grand prix SE Doesn't seem to be leaking anywhere that it is parked?
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