Hey guys, me again. As some of you know, my g/f bought a 2002 Grand Prix SE over the summer. When it came home I checked everything as usual and found brown sledge in the radiator and it was very low. So i flushed it and filled it and replaced the cap. The thing still is losing an above average amount of coolant, and the odd thing is, the resiviore stays full, or at the full mark, but the level in the radiator seems to get lower and lower every time. There is no air left over in the system from when I bled it, and no evidence of leaks on the driveway or into the crankcase. Her low coolant light came on the other day, so now its getting me worried as a car "in theory" should never loose that much coolant between august and now. We have even quite frequently been filling it assuming the air in the radiator has just worked itself out of the system (or so I've been telling her to not get her worried).
My next step was going to be to borrow a pressure tester and pressureize the system to 20psi and find the leak. However no one around here has the coolant pressure tester except for Checkers about two towns over, and every time I have called, they said "its out already".
To verify the problem isnt a cracked head/block or blown head gaslet, I was going to do a compression test on each cylinder and watch the numbers to see if they drop, and listen for air escaping the radiator cap. However if the problem is a cracked head, it may not leak unless warm.
Any ideas how i should go about this? How likely is it for a grand prix to crack a head or block? What do you guy's think I should expect? Btw, 2002 GP se 3100 V6 with 69,xxx miles to date.
Thank you for the valuable insight. If nothing else, I will thouroughly check it out, and get back to all of you soon.