Last post on Feb 29, 2012 at 10:48 AM
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Pontiac Bonneville, Sedan
#145 of 146 Areas where your Bonneville will be leaking
Feb 29, 2012 (10:46 am)
I had an 02 Bonneville that had almost all the leaks. Here is the most likely culprits:
1) Sunroof Drain Tubes: There are four drain tubes running down the four corners of the cabin. They block up and then water overflows the drip pan under the sunroof and flows down the pillars to the floor. DON'T Attempt to blow them out with an air hose. They consist of several sections friction fitted together and the air pressure will just cause the sections to separate and then it's a big problem, requiring a whole lot of trim to be removed to join them back together again. The source of the blockage appears to be small molded nipples at the very ends of the tubes. These nipples are like lips that are designed to be normally shut to prevent insects from creeping up the tubes. They are supposed to open with water pressure buildup. But like all things rubber, after several years, they become either brittle or sticky and then they don't open anymore. The solution I applied was to simply trim them with a scissors. Sounds easy right? Not so, they are in very awkward positions. To access the two front lips, remove the plastic inner fender by pulling out three plastic pins. Remove the inner fender briefly and you will see a black rubber fitting on the rear side of the fender, exiting out of the firewall/cockpit sheet metal. You can trim the lips from under the fender. Water might even rush out as you are trimming. The rear drains are accessed from the trunk, by removing the side inner trunk liners. You will see a tube coming down over the rear fender wells, and terminating in a large black plug right behind and at the bottom of the fender wells. Pull the plug towards you into the trunk, and on the exterior side you will find the offending lips. Trim them off, replace the plug and you are in business. The sun roof leak should be fixed, unless you have disconnected the tubes somehow during your tweeking. If you still have problems, you will have to drop the headliner and pillar trims to inspect for separation problems.
2) Door Trim Leaks: Water flowing down the window channel will actually flow into the passenger compartment instead of through openings at the bottom of the door, due to the slope of the door. To prevent this, Pontiac sticks a plastic sheet over the door inner to trap the water inside the door and force it to exit out the openings. Over years, the mastic sticking the plastic sheet to the door inner metal releases, and water flows freely into the cabin. Remove the door trim panel, and apply fresh sealant to the plastic sheet to cause it to adhere to the metal. Don't use epoxy, the sheet may have to be removed in future. Use mastic, and perhaps some gasket sealant.
3) Backed up condensate tube from the AC: Just like the sunroof drains, the air conditioner has a tube that vents condensate water just in front of the firewall. It also has lips that seal and they can get blocked, which causes the condensate to back up and flow into the passenger compartment. This can usually be cleared from the underside when the car is on a hoist.
Be sure to clear up your leaks. Beyond being annoying, there is a lot of electrical stuff under the floor mats, and when it gets wet and rusts, you start to experience a host of electrical problems like windows not working, seats not adjusting, etc.
Hope this helps. There are great tutorial videos on this site and on a related site www.PontiacBonnevilleClub.com that can help you with details and photos of the process for removing door trim, etc.
Updated to correct the URL for Pontiac Bonneville Club.