My girlfriend has a 04 Monte Carlo LS. Her trunk has been leaking since she bought it. Just wondering what it could be? She has gotten in the truck while it was raining today and she said that the water is not coming throught anywhere she could see. The seals all seal up to the trunk fine. For some reason there is a lot of moisture build up on the truck lid, maybe it's just dripping down from there. Has anyone had this problem before? Any advice?

 

When I had that problem on my 91 Z24, people suggested getting in the trunk while someone used a garden hose to see where the leak was. Turned out to be coming from the mounting holes for the luggage rack on the trunk lid. If she has a spoiler, have you ruled that out?

 

Doesn't have a spoiler or anything on the trunk. I think it might have been the 3rd brake light seal. I took the 3rd brake light out it was a little loose on one side. So I took it out and put it back in, made it real tight. Then took a bucket of water with her in the trunk and went over every place it could leak and nothing, so hopefully that is it. Will see if that works.

 

When you water test a vehicle, a bucket of water is not going to give you results, unless there is a large gap somewhere. You need to recreate a rainstorm. When it rains, water is hitting the vehicle at different angles and with greater force. If you have stopped the leak, then congrats, but if not, you will need to use a hose witha nozzle, and you will need to sit there for a while to allow the water to find its way into the gap.. this time will be greater if it is a small gap, like an open seam.

 

A car wash is a good test for water leaks. Since they have pressure behind the water like you find witha rain storm.

Just another suggestion for possible source of the water. Check both rear wheel housings. See if you can locate any holes where water might be able to enter the trunk?

 

I know on some older cars has a drain plug in the bottom of the trunk under or somewhere around the spare tire. You might want to check