2001 Cavalier 2.2 5-speed manual 2-door 251,500 miles.
Can I just say that these water leaks are getting really old. A couple of years ago I got back from a trip where it had rained like for 5 days and nights straight - opened up the trunk and the whole thing was a flooded mess with an ocean in the spare tire well. From that time on, I had to go without the padding/liners and stuff towels in each side - which helps a little, but when I wash the car or it rains heavy for a while - it still floods back in there. It is a real pain in the ass. I suspect that the water is coming in from the rear roof support that runs along the driver's side rear window but can't confirm this. I am at the point now where I am tempted to just put a big piece of duct tape or plastic wrap over the whole seam along that section of the roof and see if it helps.
The other place it leaks is whenever I wash the car through the blower motor / vent on the passenger side floor board. I have started to stuff a towel all up around where the bottom of the vents are along the top of the floor but that too is a half-ass attempt and doesn't really work.
Does anyone else have these problems or am I just alone in my water-logged misery?
Do you have a sunroof? If so, try covering it to see if the leaks stop.
You might have a rear leak and also another in the heater core.
Are you losing coolant?
No sun roof. No coolant loss.
Last summer during a particularly heavy rain storm, I was able to lay down with my head in the trunk and with the back seat down and the water wasn't coming through the main seal around the trunk, but instead, just mysteriously started to creep in from somewhere towards the front of the trunk on the drivers side near that roof support. Also, every time I rinse off the car while washing it - when the water stream hits the bottom of that support - a seemingly endless series of black crap.....little particles of something that I first assumed was just dirt or tree debris - keeps coming out of there so I think whatever rubber seal in way deep in there must have eroded but God knows how to even get to where I could replace it or patch it with something. I think for the forward / blower motor / vent leak I am just gonna have to come up with some kind of shield to lay over the outside of the vent under the windshield wipers. It has to be coming though there somehow.
Driver's side rear window seal? Driver door seal?
Re, the front leak,it probably isn't too hard to remove the wipers and the front plastic grille where the air comes into the heater etc.
I had the same issue with mine. Never did solve it. Had the rear window resealed and siliconed every nook and cranny. Also coated the entire trunk with undercoat and removed the air vent. Sealed the taillights. Fixed some rust, well alot of rust and around the latch. Also lowered the latch for a tighter seal. No dice. The water was leaking several places. Nailed it all down to one leak which was coming from what sounds like the same area as yours. Leaks in from behind the fender seam from upper area somewhere. Anyhow all i did was took a piece of aluminium and boxed in the gap from the fender lip to the quarter panel and sealed it with silicone. Drilled a hole in the center to allow water to escape. Not the perfect fix but least it's not all over the trunk.