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Pontiac Bonneville Water Leaks



  • I have a 1999 Pontiac Bonneville SLE I have replaced this past year due to problems with charging system a rebuilt GM Alternator, and a brand new 72 Month Delco battery and the charging rate was fine it has dropped some but not enough not to worry.

    I did last summer do a complete renovation to my AC system as I did have a leak where it would not stay charged so I did go ahead and get a new Aftermarket AC Clutch and compressor, a new GM AC Condenser, New AC Lines, and a new AC Acumulator tank and recharged the system and it has stayed charged and is sitill very cold. I did not have problems with the charging system last summer after replacing the entire AC.

    However now that the warmer weather is here and I have been using the AC more often there is a drop in the voltage meter that is at about either 11.5 or 12 volt line and it does go back up to about maybe 13 when accelerating or raising the idle with foot on the gas but when you take away the RPMs it drops?

    Does anyone know what may be causing this drop? Could it be a bad switch on the AC?

    I have also got this lousy squeal that sounds like a bad bearing some where in the front of the engine? I have replaced the AC compressor and clutch and also replaced the alternator my only other items that still would need to be replaced to try to figure out where and what the squealing is are the Belt tensioner, the Power steering pump?

  • It took me forever to try to find the leak from my 1999 Bonneville SLE which does have a power moon roof, and the leak was in the trunk the entire time and it leaked so bad that it had soaked thru all 4 sections on the rugs and the passenger side and rear passenger side were the worst of them. It appeared that the entire rear wheelwell on the passenger side was rotted out and thru as you could see clear as day and I did repair the holes and sealed it up good and wha la complete satisfaction and no leaks and dry floors after torrential rains and driving thru several flooded roads this spring.

    My way of fixing the repair was to get a piece of aluminum and shape it to the way the wheel well is and then I fastened it up with aluminum rivits to the existing wheel well and sealed the aluminum to the existing wheel well, and also sealed up all the rivits and the seams as well, and then undercoated the entire patch and have not had any leaks at all as well as the trunk staying dry and the entire floors in the vehicle.
  • pontiachepontiache Posts: 6
    2002 SLE Black...Still a looker. This weekend the drain tube will be fixed and door panels re-sealed. The carpeting has been out since November. I cleaned that immediately. (large recycle bin) (clean) 2 cups of bleach and and laundry detergent 80 gallons of water and a large stirring stick (broom). I been driving around with just the drivers seat in the car since November and no carpeting. Almost a Nascar feel. The last thing I'm going to do is drill some drain holes (just in case) and clean the wire connectors under the drivers seat. At best I'll be able to trade it in without the bad smell in the car. Hope all the windows work after cleaning the connectors. Anyone with last minute suggestions would be appreciated. Wish me luck. Pontiache
  • Below is everything that I did and now have no problems. I don't think it's necessary to drill holes. I just finished fixing my powers windows, locks and leak this past weekend. I removed all of the electrical tape,and plastic covers to expose all of the wires running from the front to the back and across (under the seat)and looked for any disconnected wires. I finally found 2 beige/tan wires that were separated from each other. Apparently, the water made the wires brittle and the separated, so I spliced the wires and used a connector, the windows and locks were repaired. I poured water on the door and in the sunroof drain holes. I found the door and sunroof were both leaking. I resealed that plastic to the door with glue and had no more leak there. Here is a link to an easy sunroof leak fix that I used which took not much time at all and worked great. good luck.
  • pontiachepontiache Posts: 6
    Mike, I'm following the advice of an earlier thread. The rubber hose did disconnect from the plastic tube. For that I will use silicone and 2 small hose clamps. I was thinking of using clear silicone for the door shields. If you have suggestions on using something else it would be much appreciated. After I pull the drivers seat back out I will do the wires and connectors. Last but not least I will get mama to give it the garden hose test while I'm in the car and proceed to the car wash for one last inspection. This has been very disheartning. I understand now why there is no more Pontiac division. Next project is the Transmission which hard shifts between 2nd and 3rd. Mine was made on Friday and hour after they made the announcment that they were going under. I'm sure of it. Cheers
  • I'm not sure what type of glue I used, but I believe it was called gorilla epoxy.good luck
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 18,054
    >I was thinking of using clear silicone for the door shields

    There's an extra sticky, gooey black adhesive for automotive use that someone recommended for sealing along the bottom of those plastic shields where the bottom "V's" directed the water to the openings in the metal to drain down.

    I recall the term butyl caulking also was used in the past. I'd check at a full service parts supply store for something that will remain tacky.
  • pontiachepontiache Posts: 6
    Thanks for the suggestions. Pontiache
  • 2004bonne2004bonne Posts: 6
    Mikelfield, I had the same problem - actually two problems. My doors leaked into the cabin (problem 1) and the flooding on the floor shorted out the wiring under the driver's seat which controlled the power to the doors. To fix the problem of the doors (its easy) you must remove the door panel. There is a 24" x 30"W thin plastic sheild that keeps water from entering the cabin. It is leaking and needs to be resealed. I forget the name of the black caulking you need but it is the same stuff they use to seal new windshields. Replace the caulking between the plastic shield and door and replace the door panel.
    to find the bad wires, I had to take this to the dealer to repair. it was under the drivers seat and they had shorted out. Good luck.
  • I have a 2002 bonneville sle with sun roof. I have water leaking in under all four rugs. Does anyone have pictures of how to get door panels off and pics of how to fix the sun roof tube leak. I have read alot of the links on here and it has been very helpfull. I thank all of you for your help and for a great site.
  • The water leaks down the window and into the door. There is a piece of hard plastic that deflects water through the exit holes at the bottom of the door. If it isn't sealed correctly, the water leaks through the panel into the floor and causes a lot of mess - electrical shorts and mold. Buy some body panel tools at the auto parts store (cheap) and pop off the door panel. It's a little tricky but take your time and you won't break anything. Tricky part is getting the panel back on correctly.

    Remove the plastic barrier, clean the old sealant off and replace the sealant with new. Its the same stuff they use on windsheild installations.
  • Thanks for the info and when i got all the panels off all the plasic on all doors was not stuck. I redid all doors and now we wait for rain to see if leaks are stopped. Thanks again
  • I am having issues and would like to see the photos you have on how to resolve the problem of water leaking in all four corners of the roof of the car. It has a sunroof and I have tried to run plastic line down them and can not find out where it it going. The two front drain holes are easy to find. It is the rear ones that puzzle me.
    Do I have to remove the head liner to get to the sunroof drains in the back?
  • Open the truck and just remove the carpet on the sides on the truck and you'll see the tubes. The tube that goes to the rubber plug to the wheel well will be disconnected from the tube that comes down from the sunroof.
  • Here is a little info
    There are four drain tubes in the Pontiac Bonneville sunroof. Two lead forward and drain down the A Pillar entering the car's front cowl sheet metal and exit in the gap between the cowl and fender inner. The drain ends are invisible without removing the fender inner.
    Two others lead rearward and drain down the C Pillar and lead off into the trunk and exit through the sheet metal just behind the wheel wells on both sides of the car. Remove the side carpets in the trunk and they will be clearly visible. Black 3/8" tubing leads to a 1" rubber grommet passing through the sheet metal right down where the fender inner meets the trunk floorpan. Pull the grommets out of the sheet metal and cut off the little lips you will see on the outside surface. They get stiff or stuck together and tend to block water from draining. It just backs up and overflows the drain pan in the roof. Or possibly the tubes will be disconnected at the elbow molded into the inside edge of the grommet. If you have water in your trunk, they are disconnected near the grommet. If you have water in your passenger compartment they are backing up and overflowing the drain pan.
    The drain tubes push fit onto a plastic drip tray that catches the rainwater coming through the sunroof opening. Pontiac's intent was not to seal the sunroof against the roof sheet metal. Instead, they allowed for a gap, and then caught the moisture in a plastic catch pan with four drain outlets - one on each corner of the pan. The first leakage problem is that the drain tubes sometimes separate from the plastic tray outlet. You have to drop the headliner to verify this. The second leakage problem is that the drain tubes in both front and rear are made in sections and they can separate. The third problem is the sticky lips on the rear grommet. The fourth problem is plugged outlet holes behind the fender inners on the front drains. There may be a fifth problem, of debris blocking the tubes themselves, but so far I have not found that on my car.
    Hope this is helpful.
  • Here is a little more info. Another good site to visit is
    for information about Pontiac Bonnevilles. The owners there are very knowledgable.

    Here is a specific forum on that site, where water leak issues are discussed and several great photos are posted.

    Here are more links dealing with known leak problems causing wet floors

    sunroof drain line connections become disconnected ... =43&t=1688

    Door rain shield seal repair ... 43&t=11470

  • Took care of my water leak problems 2002 Bonneville, carpeting and interior back in. Driver window works, but not the other three windows. They don't work from the individual switches or the drivers console. I have a gas gauge the is irradic, but other gauges seem to be OK. Before I put the carpet and seats back in I checked the connectors and grounds and seemed fine. Anyone have similar issues ? Any and all suggestions welcome.
  • Like everyone else I am getting water on the floor behind the drivers seat and underneath it. Have spent money fixing the wiring because of this. I am now also getting water in my trunk where the spare tire sits. Can anyone help me?
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 18,054
    edited February 2011
    Look for the corroded connector where the tan or brown wires are connected under the driver's seat rear area. This is the communication to the other three doors for windows.

    This shows it. It is not my picture. It where the red connector binds all four wires in a connector that corrodes.
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 18,054
    I've read where people have a hole in the wheel housing due to corrosion. The spinning tire pushed water into the trunk. I've read about leaks with the air dam on the trunk. I've also read about leaks around taillight housings.
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