2002 Grd Prix Coolant loss question

In July my coolant light came on, I put coolant in the car, then in about Sept I had to put more in...then when I had an oil change done in Nov. They said I needed a new radiator cap because they said there wasn't any leaks...and well there wasn't any coolant under my car or lying on the ground...then we replaced the cap to discover that is not it either, I needed to put more coolant in my car yesterday the light came on again and the car is dragging, once it gets warm I guess it drives better...it seems like a it drags and drives like its a 4 cylinder verses a 6 cylinder. Any way the car has 129,000 miles on it I drive it 122 miles a day. So I thought I was just eating up coolant because of the miles etc....I want to know if anyone knows whats happening with the coolant..by the way, when I get out of my car I can smell the sweetness of coolant but don't see a leak, but it has to be going tosomewhere....a mechanic I called said its probably going into the engine>????? Please advise, thank you.

Depending on what engine you have, you have one of two problems. If you have a 3800 engine, you have a cracked plastic upper plenum or a bad water pump. If you have the 3100 engine, you have a lower intake gasket failure or a bad water pump. Water pumps will usually start to leak worse and worse until finally they either seize up or are throwing coolant all over under the hood. The two intake problems will result in coolant loss through the engine. The 3800 engines suck the coolant into the cylinders and out the tailpipe. The 3100 engine sucks the coolant into the oil, and will turn the oil milky and leave "butterscotch pudding-like" deposits on the pcv valve, oil cap and underside of the intake.

Depending on what engine you have, you have one of two problems. If you have a 3800 engine, you have a cracked plastic upper plenum or a bad water pump. If you have the 3100 engine, you have a lower intake gasket failure or a bad water pump. Water pumps will usually start to leak worse and worse until finally they either seize up or are throwing coolant all over under the hood. The two intake problems will result in coolant loss through the engine. The 3800 engines suck the coolant into the cylinders and out the tailpipe. The 3100 engine sucks the coolant into the oil, and will turn the oil milky and leave "butterscotch pudding-like" deposits on the pcv valve, oil cap and underside of the intake.


Thanks for the info richtazz,

I believe my car has the 3100 engine. Question though, if that is the case and that is the engine in my car, wouldn't the people changing my oil see the milky color?...When they showed my the oil it looked its normal dark brown color.

Plus I forgot to say in my original email my car is eating more oil lately, that is why I didn't think much of the coolant loss either, I just thought since I have put soo many miles on such a young car that I was just getting to the point where the car needed things more often ie running harder, needing more oil, coolant etc to keep the poor thing going. So we were checking the oil quite often since it nearly sucked itself dry of oil one time not too long ago about 4,000miles after the last oil change.

The place that the intake gasket fails is between the coolant transfer passage and the intake port on cylinder 5. Your gasket may have failed in such a way that instead of the coolant getting into the oil, both oil and coolant are being sucked into teh cylinder and burned out the exhaust. Does your exhaust have a sweet smell to it, or is it puffing out bluish smoke? If so, then that is your problem.

The place that the intake gasket fails is between the coolant transfer passage and the intake port on cylinder 5. Your gasket may have failed in such a way that instead of the coolant getting into the oil, both oil and coolant are being sucked into teh cylinder and burned out the exhaust. Does your exhaust have a sweet smell to it, or is it puffing out bluish smoke? If so, then that is your problem.


Yes, I would have to say that my car has a sweet smell to it. I noticed it yesterday when I got home from the grocery store...that is exactly what I smelled.

What do you think the financial damage will be...maybe that might be too hard to be determined, I live in Michigan and the cost might be different in other states....thanks for the info.

I live in Flint, MI and the going rate around here is $650-$800. Make sure that when they do the job, they clean the sludge out of the valve cover baffels and change the thermostat. Also, there is an o-ring that is famous for leaking oil that is easy to get to while the intake is off, it's for the oil pump drive shaft. Have them change that too while they have it apart, it's one more bolt and about 10 extra minutes, so don't let them charge you too much extra to do it. Just for educating purposes, they may tell you that replacing that o-ring is a 2 hour job, but that's only if that's all they are doing.

I live in Flint, MI and the going rate around here is $650-$800. Make sure that when they do the job, they clean the sludge out of the valve cover baffels and change the thermostat. Also, there is an o-ring that is famous for leaking oil that is easy to get to while the intake is off, it's for the oil pump drive shaft. Have them change that too while they have it apart, it's one more bolt and about 10 extra minutes, so don't let them charge you too much extra to do it. Just for educating purposes, they may tell you that replacing that o-ring is a 2 hour job, but that's only if that's all they are doing.


Hi Richtazz,

Thanks for the information...I guess my issue was the intake manifold? I just posted another issue they are having trouble with regarding my car, it is running sluggish, its a 6 cylinder but it takes off like a 4 cylinder, like its pulling a heavy trailer...do you know what that could be, they tried replacing a coil of some sort and I believe they tried ignition moduler or something like that and that is not it...by they way, they did replace my thermostat, I am not sure if they did the other things you mentioned because I did not read your other response until it was already completed, thats my bad.

Hi, boy richtazz I hope this is your full-time job...you are very active in this.
I have a 02 GT with the 3.8, there is the odor of coolant at times, I checked and seen some anti freeze below the plenum/intake. I cleaned it pretty well and am waiting to see it were it is coming from. Is there a common area if it is the plenum gasket? Also is it difficult to replace this? my car is not Supercharged.

If the coolant leak you had was severe, you may have a plugged up catalytic converter. Antifreeze sticks to the grid in the convertor and can plug them up, resulting in sluggish performance.

HDL, got your PM. My suggestion is to have engine vacuum tested with an automotive vacuum gauge (0 - 30Hg). There are plenty of tap off or tee in points on the intake manifold and throttle body. Good engine vacuum is nothing less than 15 inches. If your engine is running that poorly the test may reveal a lot without guessing or wasting money on parts that may not fix the problem.

A vacuum test may reveal whether you have a leaking intake manifold gasket, other engine issues and even whether the CAT convertor is clogged.

I have a procedure to test the CAT and exhaust backpressure with a vacuum gauge. Most auto mechanics have one and they are available at places like Autozone for around $25.00 - $30.00.