Trunk Area Waterleaks
2000-02 Pontiac Bonneville

Condition
Some customers may comment that water leaks from the deck lid when it is opened.

Cause #1

The CHMSL lamp gasket may not be seated correctly. Refer to the illustration above.

Correction

Important
If any part of the CHMSL lamp gasket is cut, torn, or folded over, the gasket may become unseated and a water leak may occur. Water will run down the edge of the decklid and leak into the decklid, past an unseated CHMSL lamp gasket.

1.Remove the CHMSL lamp assembly.
2.Inspect the gasket for damage. If the gasket is damaged, replace the lamp assembly.

3.If the gasket is not damaged, run a small bead of silicone sealer around the perimeter. Refer to the illustration above.
4.Reinstall the CHMSL lamp assembly and tighten the fasteners securely.
Cause #2

The decklid rear applique may not be completely seated. Refer to the illustration above.

Correction

Important
If the decklid applique is not properly seated, up to 3.8 L (1 gal) of water can run down and collect in the decklid. When the decklid is opened, the water will pour out of the five drain holes. Three of the holes will drain water onto the rear glass and the other two holes will drain the water into the trunk.

1. Use sufficient force to press the applique into the decklid completely.
2. Securely tighten the applique retaining nuts from inside the decklid and re-test.
3. If the leak persists, remove the nut(*) and apply a thumb grade sealer to the applique retaining studs. Reinstall the nuts securely.
Cause #3



The rear spoiler retaining nut(*) may be loose or missing. Refer to the illustration above.

Correction

Important
If any of the six rear spoiler retaining nuts are loose or missing, a potential water leak condition may exist. If the water leaks through a loose spoiler fastener, water will fill the decklid overhang and enter the trunk when the decklid is opened.


Tighten the six retaining nuts securely and re-test.
If the leak persists, remove the nut(*) and apply thumb grade sealer. Reinstall the nuts securely.
Cause #4
The sheet metal may leak water through welds behind the rear body applique.

Correction
Remove the rear applique.
Clean the sheet metal with one of the cleaners listed below.

Apply seam sealer to the sheet metal weld area. Refer to the illustration above.
Reinstall the applique securely.
Parts Information
3MŽ General Purpose Adhesive Cleaner, P/N 08984
Dominion Sure Seal, Sure Solve Stock BSS
Kent Acrosol™
3MŽ Strip-Caulk-Black
3MŽ Clear Auto Sealer, P/N 08551
Silicone Rubber Sealant (Black), P/N 12345739 (in Canada, use P/N 10953541)

Made STICKY by your friendly neighborhood Administrator. As the rainy season descends upon us, this will be invaluable info for our owners.

Thanks again, to PontiacDad.

The first time my wifes trunk leaked was because the sunroof was improperly adjusted which caused it to leak and the drain lines came undone.

Hey, thanks for the info and diagrams! Even though I can do this on my own I may have my dealer do it because I'm under warranty. Either way, If it happens again I'll be able to fix it.

this happens to me all the time after it has rained, yet for some reason it had never occured to me to get it checked out. Thanks for the info

Thanks PDad. Although mine is not a problem at the moment, I will keep this in mind. I have been told that this is a problem on our cars.

Thanks again...and your nic rocks!

:( I have found that my leaks were (are) coming from the weld in the trunk itself. It did leak in the side area of the truck lid, but I sealed that. There is a weld on either side of my trunk where the water could pass through. I was able to seal the passenger side, but the other side did not set up before it got wet again. If you look next to the rubber seal around the trunk you find the welds on either side 10" down from the rear window. Once it is dry I will try to put some silicone. FYI

Had a really bad trunk leak while my 2000 SLE was still under warrantry. The spoiler was the problem, the dealer reseated it and sealed it. Now, three years later, I am starting to get another small leak, not near as bad as before, but annoying. I am going to try the leak stop methods above, but my first stop will be the spoiler again.

If you have water in the driver’* side floor of your trunk and/or in your wheel well you might want to check the drain rail from your moonroof. (I didn't believe it either.) The easy way to check is to run water all over your trunk lid, spoiler and lights - then check for water. If the trunk is dry, run water over your moonroof. Then check it again. It might save you a lot of time and $$ versus changing seals. It worked for me....

This would be another area to look for source of trunk leak on the newer Bonnevilles.

This is a shot looking out of trunk towards area of right rear tail light. There is body seam material to seal the interior sheet metal seams. I temporarily used plumbers putty to stop the leak. My spare tire well had like 4" water in it after heavy rain & the trunk mat was soaked. The drain rails on the deck lid (either side of deck lid) should end up draining down through bumper area, but some drainage would find its way into trunk via the bad seam right side only. Left side appears to be sealed correctly.