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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 & I75 Posts: 21,507
    >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.

    2015 Cruze 2LT, 2014 Malibu 2LT, 2008 Cobalt 2LT

  • 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 & I75 Posts: 21,507
    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.

    2015 Cruze 2LT, 2014 Malibu 2LT, 2008 Cobalt 2LT

  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,507
    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.

    2015 Cruze 2LT, 2014 Malibu 2LT, 2008 Cobalt 2LT

  • I believe that the water leaks came from the sun roof. I replaced the front two with clear tubing that fit inside the existing corrugated tube very well. The two rear tubes were solid but clogged. The flexible plastic grass cutting line worked well until there was a clog that was stuck. Some compressed air in a can did the trick there. All seems well now.
  • You've got to find where the water is getting into the car's cabin. I had it coming in at two places -- just behind the parking brake pedal on the firewall and through the driver's door. Put a water hose on the roof of the car and the driver side door and sit inside. I took out the carpet and the driver's seat so I could find the leak. It's not hard to take out the seat but the center console is a bit difficult. Be patient and take your time. Don't force things or you'll break them.

    If you've got the firewall problem, that's easy. I put some silicone sealant in the hole and it stopped.

    If there is a leak coming into the cabin through the door (you'll usually see it coming in between the door panel and door frame, you've got to pop off the door panel. Use some plastic tools from Harbor Freight (cheap) and pop off the door panel - take it slow and easy and don't break the clips that hold it in place.

    Inside the door is a plastic shield that is supposed to keep the rain water from leaking into the car and directs it down to the drain holes at the bottom of the door frame. What happened to me is the SEAL that keeps the plastic shield tight agains the door frame fails. The plastic shield needs to be removed and resealed. The sealant is the stuff you put on your replacement windshield. You can get it at the auto parts store. It comes in a box and is a long string/bead of sealant. Remove the old sealant on the plastic shield and put the new stuff on. It's real sticky and adheres beautifully to the metal door frame.

    Reinstall the shield, put the door panel back on and let it cure for a day. Try the water on the door again and see if it leaks before you put the carpet back in.

    You might try your other doors for leaks too. Three of mine leaked.

    Good luck.

  • i pretty much have all the problems people have been having on this forum. i need that email with help...any help will do, i have water everywhere. All drain tubes are clogged and wont blow out. Im thinking about putting new tubes in. is my email
  • kts0347kts0347 Posts: 44
    edited February 2012
    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 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.
  • bentstorkbentstork Posts: 1
    I have a 2002 Bonneville SLE, I have owned the car since 2009 and started developing water leaks summer of 2012. The right side of the interior would get wet, both front and rear carpeted areas. The rear especially as that is the lowerst point. I vacummed most of a gallon of water out of the carpet twice that summer. As others have done on this forum I took the time and removed the seats and console and stripped the the soaked carpetting out and let them air dry. I did the wet tests, running a hose on the outside. I discovered 3 leak sources and fixed two of them. The plastic shield on the front right door was the main culprit. Everything seemed fine and good over winter and even in this spring until recently. But again wet floors. So again I stripped everything out and started over. The leak now is coming from under the firewall in the extreme right corner. I have no idea where from and really don't wish to strip the dash down. Does anyone have any idea where it is probably running in and if there is a easy fix? Thanks
  • kts0347kts0347 Posts: 44

    I had a 2003 Bonneville and had ALL the classic water leaks. Glad that you have conquered the leaking door seals. They will all become loose in time and a good sealant is needed to cause them to retain a relatively permanent bond. I initially tried household sealants and they survived only a matter of months before re-releasing. Save your energy on a repeat repair and get a good automotive bonding product such as I describe below, from an auto supply store.

    You didn't mention whether you have a sunroof, but the source of the current leak points to sunroof. There are four vent tubes that drain water that enters the roof around the perimeter of the sunroof. It's not designed to keep water out. Rather its designed to drain the water off. There is a drain pan surrounding the sunroof, and there are four drain tubes. When the tubes block, the pan overflows onto the headliner, and flows down inside the trim pieces until reaching the floor. The front of the roof is the lowest point hence the water drains off the headliner into the windshield A pillar trim, then down the side kick panel trim eventually finding the carpet.

    Two tubes route down the front windshield pillar, out through the sheet metal on the side kick panel under the IP, and ultimately dump to the open air behind the plastic inner fender panel.

    The other two route down the rear window pillar, into the trunk and then dump to the open air behind the wheel well.

    I initially thought that the tubes were plugging with debris and mud, and I tried dropping the head liner and blowing them with compressed air to clear them. Bad idea. They aren't a single run of tubing, instead they consist of a series of tubes that are interconnected one inside the other (pressure fit). Blowing with compressed air simply causes these connections to separate, and then you have a real problem getting them reassembled and have to remove a lot of trim to access them.

    However after much work, I finally found that the real blockage wasn't inside the tubes, it was at the very end, exiting out of the car. The engineers designed the tubes to pinch shut to prevent small insects from entering the vehicle. The weight of the water accumulating in the tubes is supposed to provide sufficient pressure to open the pinched ends and it works - when the hoses are new. After several years these pinched ends become a bit sticky, and simply don't open and thus the water overflows. I solved my sunroof leak problem permanently by simply clipping off the pinches with a wire cutter. The rear ones are relatively easy to locate. Just pull off the trunk side trim and you will observe the hoses snaking down and over the wheel well and finally making a tight turn to exit the sheet metal. There is a grommet on the end of the tube where it exits through the sheet metal that you can pull out to reveal the pinch point that you want to snip. Just push the grommet back in the hole and the job is done. In order to remove the side trim, no tools are needed. The hard plastic piece crossing the back of the trunk has to be removed by hand unscrewing some black plastic knobs. There are some similar black plastic knobs securing the side trim.

    The front tubes are a little harder to access. The plastic inner fender has to be removed. This can be done with the wheel in place with a little practice. Pull out the plastic push clips around the fender opening perimeter and the inner fender will be loose. Then just try to get the rear part of it free so you can access the hose exit point. You can snip the pinch point off with the hose in place in the sheet metal.

    Then test the whole system with a hose and ensure that you get water flow on all four corners. Just look for puddles on the ground since you won't be able to see the actual hose ends.

    PS: There is the same pinch system on the end of the hose that drains condensation out of the air conditioner. This can also stick and cause condensation water to overflow the HVAC and leak into the passenger compartment.

    Another source of water leaks that I encountered was in my trunk. My spare tire well would fill with water. I discovered that water would leak at the rubber weatherstrip. Not over the top - instead under it, where it was stuck on a sheet metal lip. The solution was to pull it off, and reseal the weatherstrip to the lip with a good dollop of glue all the way around. I used Pro Seal brand black RTV silicone Instant Gasket, that I purchased at the auto supply store.

    I also had two other sources of trunk leaks. The tail light attaching studs that pass through the sheet metal are secured with nuts backed with a mastic. Eventually they started to leak. The Instant Gasket worked here too. The final source of trunk leaks was the rear window itself. The mastic used to secure the window eventually developed leaks on the lower edge due to the design that accumulates water. A coating of sealer from the inside of the trunk provided a clean finish outside and solved the leaking problem.

    Best of luck. I operated my car in the heat and rain of Florida, it was black color and I kept it outside 24/7 for its entire life so it endured the ultimate of endurance tests. Ultimately all the factory seals failed but fortunately they were detectable and easily repaired - - if I only knew where to look and what to do. The discovery part was the big time consumer. Hope this write up helps you to shortcut the repair time.
  • cohlmcohlm Posts: 1
    I also have a 2000 Bonneville LE with water accumulating in the rear driver's side floor board. I have noticed prior to this that my trunk would have a slight amount of water droplets, but I thought it was dripping from my trunk lid when I opened it. I had a previous 1987 Bonneville SE that did the same thing and supposedly it was coming from a trunk leak. I was able to afford to have a mechanic fix it at that time, but I am now not able to afford having it repaired. I could use any help that you could offer for me to help get this problem solved. I do have a sun roof as well, Could the leak be coming from there since I have noticed the trunk being affected as well?
  • Hi, I also am having a water leak in my 03 Bonneville. Could you please send information to me on what to do. I do not have a sunroof.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 58,496
    You might want to scroll through previous posts here. There's a lot of good info on what to look for.

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