Hi all....I'm new to the list. I've wanted to own a Bonneville GXP since they came out, but couldn't afford one new. Even knowing about their typical problems after 4/5 years of reading about them, I was finally able to get my hands on one WITH a full warranty. I bought an 04' Diamond White GXP with 34K miles on it. I love this car!!!
Even though I have a warranty, I'm a hands on kind of guy and at least want to investigate my antifreeze leak problem before I take it to a dealership and blindly trust what they tell me is the problem.
Description of problem: Before I purchased the car, I placed it on a rack and checked the underside for leaks of any type. The car was bone dry. I checked all fluid levels EXCEPT the coolant level before the car went up on the rack. The car was hot and I didn't want to mess with the coolant cap and the pressure. When I got the car home and cooled, I filled up a coolant reservoir that was about a 1/3 of a gallon low. The next day I see a puddle of antifreeze under the car, almost center, favoring the drivers side by about 10" past center.
The car DOESN'T leak while running. It doesn't leak while hot and parked. It only leaks after I have parked the car for the evening and it has been allowed to get bone cold.

Am I looking at a water pump issue or a water pump gasket issue? I'm thinking gasket issue. If that'* the case, can I simply try tightening the bolts to rid my leak, or can I even get to the bolts?

Thanks,
Gary

The engine is so new to us here, and me as a GXP owner, very little has been done mechanically. And as you mentioned, most of us have the full/extended warranty. That makes you a pioneer! LOL (Doesnt help,..... did it.) Some users have mentioned an erratic coolant light (including me) but when checked(always later for me), nothing is wrong/low. I suspect enough is going into the coolant bottle at might to trigger the alarm and it returns as the engine warms. But you say coolant is on the drive. Did you fill the Bottle beyond the mark? One member reported a crossover leak in the rear of his enginem but had it fixed by Dealer Service. Havent had a report of the waterpump housing leak, but it'* always a possibility. And can be checked without a big hassle. Pleased keep us informed, as I mentioned, most of our engines are still under warranty, and the way they crammed this V8 in there, not alot of actually owner service for us to refer to yet. If you have the chance to get the GMPP extended warranty, It'* a good idea and more than half here have it. Aftermarket warranty'* are nothing but trouble.

Try filling the overflow again. Then at night, stick a few paper towels around where you think it'* leaking. Then in the morning pull them back out and make a note of any coolant on the towels. This will at least give you a much better idea where it'* leaking.

I did have a coolant leak. The problem turned out to be my water pump. Since it was replaced, I haven't had a single problem (I estimate about a year ago). Of course there are any number of different possibilities. If you have a full warranty, a dealer visit may be in order (even if you'd like to know ahead of time). Keep in mind that "blindly" trusting the dealer isn't as bad with a warranty as without. I'm sure you know this already, but the water pump is on the driver side. This of course doesn't mean that'* the side the leak is actually on. I've had several cars in the past that have had antifreeze leak, drip down onto other parts to be carried to a completely unrelated area before dropping to the ground.

Thanks for the input guys. I'll be taking it to the dealer and find out what they say. Like you mentioned, the warranty will pay for the replacement of the pump or whatever it may be.
I'm sure I'll be back with many other questions related to this car and it'* goofy traits
Gary

I have this same leak/symptoms. Hopefully it is the water pump so my extended warranty,(not GMPP) will pay. Please post when you find out.

me to these cars have many problems

Yes they do. I must have a factory freak for sure. I have the extended GMPP but haven't had to use it for anything. (Knock on wood). 38k miles, WOT all the time, nitrous injected, and yet not a problem so far other than the IM shaft. My warranties up @ 70,000 miles and I have a feeling the engine will fall off it'* cradle at 70,001.

Well, I had the leak diagnosed and it'* the crossover pipe. This is the gasket between the water pump housing plate and the block. My extended warranty IS going to cover job. Estimate was for $595. My car now just turned over 29K in mileage. This is a disgrace that at this mileage, I've had almost $2K in repairs done. 80% of it under warranty. My last Poncho, '95 Grand AM GT, was nowhere near this unreliable. I really like the car, but am uncertain if I can continue with these headaches. GM has basically said F U to all my inquires [sic]. All these problems don't give me a warm feeling inside about doing business with GM in the future.

GM has told me to screw myself over enough times already. I bought an aftermarket warranty (Nissan Quality Guard Plus Deluxe), which has covered everything so far. Here'* a short list to give you an idea of what you should expect. I now have nearly 60k miles.

- Front left and right wheel hubs
- Coolant crossover pipe
- Water pump housing gasket
- Steering shaft (typical)
- Gauge cluster (temp gauge fell)
- Front engine mount
- Fog light wiring harness (ended up installing HIDs)
- Steering gear (expensive as hell job)
- Ignition coil assembly (blown while WOT from 0-50)

I'm going to assume for now that the owner who had the car before me abused the hell out of it. Serviced at a Chevy and Cadillac dealership, my warranty has forked over $5400 in repairs so far, and I still need to spend $65 to replace the oil cooler lines.