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Pontiac Bonneville Water Leaks



  • Hi imidazol97,
    Can you also send me the guide for drainage repairs?
    - 2000 Bonneville
    - No sunroof

    I noticed water on driver's front floor. I pulled up the carpet in the front only to find that it was wet under the seat and on the floor near the rear seat. Again, only on the driver's side. I have removed the seat and am drying the carpet out. But I haven't found the source of the water yet.

    Is the A/C drain tube in the firewall on the Passenger side or Driver side?
    Could water going into the cowl find its way into the cabin somehow?

    I also noticed that most of the weep holes in the rubber seal around door openings (not on door itself) were not punched completely during manufacturing. I had to use tweezers to remove excess rubber from weep holes.

    Tonight, I will check to see if water is coming in through the door. Perhaps, I need to caulk....

  • I have the same problem in my 1997 Bonneville. Could someone please send me the fix as well? Thanks.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,311
    I sent data to your email account.
    Go to the top of this page and in the light green bar under the Home in the dark green bar is a link, My Carspace. That is your carspace page which includes and email account. The email address in the account is your username,
    Some may not receive email from outside Edmunds Carspace. But it works sending emails within Edmunds.

    Good luck

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

  • I just checked my Edmunds email account, and there wasn't anything in it. Could you please try again? Or I could just give you my email address and you could send there? Let me know. Thanks!
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,311
    Click on my user name in a post I've made and you'll see an email address listed.

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

  • I have a 96 also, I have had a water problem on and off. I found my answer myself. it may be coming from under the windsheild wiper area. take the wipers off and remove the screen cover, there is a air intake channel about 8 inches x 4 inches under a plastic sheild. I had to modify the sheild. and i also bilt up a lip around the channel with calk (quad). its for exterior siding. I havent had any water problems after i did this modification.
  • Interesting. Was it coming in on just the driver's side or both? I'll have to have somebody take a look at that.

    I have water coming in on the driver's side, pooling in the back, and the dealer wanted $600 to replace the rubber around both doors. I'm not convinced that's the issue, although the doors do leak. So now I have a few things to look at. Wish I had a someone handy with these things so I don't have to rely on the dealer or service station.
  • It was mostly on drivers side, but it came on passenger also. the water damage caused a couple of other problems. (electical). It had corrioded ground wires under carpet. on the drivers side next to the rocker panel. My car wanted to stall out, windows would stop, seats would stop, and the air bag light came on and stayed on. now I have a bad air bag module. I also have issues with my dash cluster. all caused from water. It didnt happen over was caused from leaking for about ten years.
    PS. drill a couple of small holes in floor front and back. this will allow the water to stop building up.
  • Wow -- I had the same thing. The car stalled out on me about a month ago, and it was due to corroded wires under the carpet. Cost me almost $400 to have that fixed. Replacing the wires also took care of the one rear window that wouldn't go down, but the car still gets wet, and lately my airbag light comes on, too. Does that mean that the airbag won't work?

    I'm not sure I want to drill holes in the floor -- isn't there a safety hazard with that?

    I'm not really handy with cars, so I have to figure out who I can take this to. Thanks.
  • I was told that my air bags wont deploy. Drilling the small holes wouldnt be a safty hazard. all cars come with flood plugs under the carpet and rubber sound deadener. the plugs pop out to drain heavy water. I just drilled a couple small holes where the water built up the most. a couple of 1/8 of a inch size holes. the air bag module would cost over $400.00. I am not getting it replaced. the car is very nice, however I cant keep sticking a ton of money in it.
    PS. look for a auto electric garage, and see what they recommend. I hope all info was helpfull, Good luck. John.
  • I have a 2005 bonneville se, some probs:
    1. i had the ac control lights replaced 2 years ago, now the same prob. rt 2 lights are out dealer say so
    2. my trunk has water i have a sun roof
    3. my tack sometimes does pushups. seems to loose power when speeding up
    then it works ok
  • Rocky74 & rmgoat78 - I'm new to Edmonds and have not seen the answer to this problem. I've got a 2004 Bonneville SE with a wet floor behind the driver's seat. Tell me what's wrong and what my fix is --- PLEASE! Thanks

  • rocky74rocky74 Posts: 15
    I just re-read your post about cars having flood plugs under the carpet. Do you know where they're located on the Bonnevilles? That might be a good solution, to just
    pull the plug when water builds up.

    I can't figure out my car -- I vacuumed up the water from the floor in the back seat, and a couple of days later, there was MORE water in the back seat. Where could that have come from? It didn't rain in those 2 days.
  • rocky74rocky74 Posts: 15
    Imadizol sent me the fix. He's the expert. If you can't get in touch with him, I'll try to find his post and forward it to you. It involves taking the door panel off and re-sealing the plastic liner inside the door that keeps water from coming in. I haven't done this yet as I don't know if I want to be messing around with trying to take the door panel off myself.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,311
    If you have a sunroof it can be the tube drain cracked off at floor level near the emergency brake. But you don't mention front floor wet. There is a rear drain along with front drains on each side. Lift rear seat cushion and look for water coming from the rear. If none, then ...

    But most likely is inner panel in the door. See my message in your email. Click on the My Carspace in green bar at top of this page. That takes you there; or

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

  • hi,
    i have a 05 se, my leak is in the trunck. it comes from my sun roof, hoe's your tranny
  • Hello there,

    I too also do have a 1999 pontiac bonneville. I have had several times of a tremendous amount of water in the trunk that was where I had first seen the water and was trying to track it down and for months was unsuccessful until I took off the tires to rotate them and looked into the rear fenderwell and to my admise I found that the entire fender well was rotted out. It was a very big piece of cancer on the body and was hidden well with the undercoating. I have to still repair the fender well and hope that will cure some of the flooding that my car seems to be getting as I have it in the trunk to the back seat and also the front seat as well as it seems to travel underneath. I also do have a sunroof as well and will have to check on the drains to see if I can find out if they are clogged. Does anyone know where all the drains are located at and where they would drain out to and end out coming out of the body at so that I can try to fish some wire up there to open it up as well as some air from air compressor?

  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,311
    I have read once of someone having the wheel well rust through and allow wheel splash water into the trunk. They repaired it with a piece of galvanized metal and rivets and silicon caulking.

    For the sunroof, do not use compressed air because it may pop the hoses off the connections and then you will have a leak. You might try suction from a shop vacuum to draw gunk back up and out.

    Test by using small amounts of water into each corner of the sunroof and watch to see if it comes out. For the fronts, they drain behind the front wheels. I do not know where the rear drains empty.

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

  • I Recently purchased a 1995 Bonneville with significant headliner damage and very wet floors (all 4 floorboard areas) I suspected, before I purchased - that it had the notorious sunroof drain tube(s) problem that is mentioned in many forums. I am in the process of gutting and replacing the headliner, however I was fooling with it tonight in order to perform a temp fix on the drain tubes and found the following problems:

    The drains are made of very brittle plastic. I put this subject on the top 10 design and manufacturer blunders of all time! I have had sunroof cars for over 25 years, and I don't think I have ever experienced such inferior made products, in such an important area of an automobile. Not only do people on these forums ask where they can ‘pull the plug’ in the floorboards, but also some mention that wiring is corroding because of water damage - all of which has possibly happened in as new as 2005 models.

    So anyway, after removing all the screws and plastic clips, I partially pulled back the front passenger corner of the headliner. There was evident water damage in this area where the material had separated from the foam backing of the headliner. Carefully pulling the corner away from the pillar, I noticed the 3/8" size black-brittle-tubing (loom or flex style tubing) had separated from the drain boot on the sunroof pan. As I gently touched the tubing a 3" section broke off and fell apart in my hand. As a side note, I involve and teach my children about cars and at the time of this issue, my 16 yr. old daughter and 10 yr. old son witnessed this diagnosis - they both concluded it was unnecessarily bad drain tubing. I also removed the front passenger fender to check for blockage at the end of the drain system, for which I did find a very large mud blockage that could have been a restricting factor had the system not already been compromised in other locations. I suspect that the drivers side front fender will also have some sort of debris blockage.
    Note: you can not see this particular blockage without unbolting and spreading the fender and fender-well away from the inner structure of the car, basically removing the front fenders.

    I am an experienced fabricator with knowledge in the manufacturing and automotive industry, so fixing this problem (the right way) is not going to be a problem. Whatever advice that any of you would be kind enough to reply, will be appreciated and considered. I will also post any helpful information after the repairs have been performed.

    Before I go any further though, does any one know for sure if there are additional drain tubes in the back of the sunroof pan toward the trunk? The windshield has a crack in it and so installing a new headliner when I replace the windshield will be much easier, but I wanted to be more prepared with additional tubing if I knew there were more drains?

    I think we would all agree..... besides the mere purpose of getting from point A to point B in an automobile, we would like to stay warm in the winter, cool in the summer, and by all means, dry all year around!
  • rocky74rocky74 Posts: 15
    To Syberbrat:
    I am very impressed with your work on the front fenders. I'm just a middle-aged female with no particular skill regarding cars, so I am not able to do this work myself, and trying to figure out where to start to get the leaks worked out. You wouldn't happen to live near me in PA, would you? I could use some help. :-)
  • sammz111sammz111 Posts: 2
    I just purchased my first car last week a 2000 Pontiac Bonneville SE (no sunroof)

    Today i got new car mats and went outside to go change them as i started to take the old ones off i noticed they were damp (it rained a day before) so i put my hand directly on the floorboards, the back ones had so much water underneath them that the best way to describe it was like a tiny water bed and they were completely soaked, we then checked the front ones they were soaked as well but not like the back ones, i then opened up the trunk to find that when i opened it the water must have been in the spoiler because it leaked right into the trunk. The trunk was also completely soaked along with the whole trunk mat. We found i guess the "A/C condensation Drain plug"? i was reading other posts on this site and my dad put a screw driver in it and for a good 30 mins water was rushing out of that little thing. Then when i went out later that night the car was completely dead so im not sure if this water had something to do with it :( Also nothing else in the car was wet just the floorboards and all the seals on the doors look good but i dont know anything about cars.

    From what i can tell though something is definitely wrong with the trunk but that was the least wet part in the car so i cant really see that just from one rainfall all that water got into the car just from the trunk.

    I really am not sure what the problem is, could it have just been that the trunk had a small leak in it and the last owner never knew and that it accumulated so much over time and the a/c thing was clogged that, that is why all that water was built up there....or do i have a bigger problem on my hand where i have some monster leak somewhere

    Anything would be great just so i know where to start and if this is a problem Bonneville's have

    thanks, Sam
  • Dear Sam,

    I just wanted to let you know that I too did a posting in here several months ago as to water issues with my 1999 Pontiac Bonnevillle SLE. I do have a sunroof though but upon review of the car and checking it out thoroughly I found a HUGE HOLE in the passenger side rear quarter panel wheel well where I would say I must have taken out about 12 gallons of water from as I had to empty my shop vac 4x and if you look under the spare tire area I had about 2 inches of water in there not to mention that the padding that was in the trunk was water logged as well. It appears that since I repaired the holes that I found in the rear wheel well that all is fine now and we have had some severe flooding here in NJ and I have been thru water that was up to the doors and since the fix of repairing the holes with a sheet of aluminum and some clear waterproof silicone sealer and lots of aluminum rivits as you dont want to use steel as to the rust, and then undercoated the aluminum with rubberized undercoating to protect even further. it appears there are no more leaks in the trunk and my floorboards are dry. I was even thinking that oh boy I will have to send out the vehicle to the sunroof shop to clear the drains out which I still will do as it has been 11 years but all is dry and I am very happy I hope that maybe you find the same problem and are able to fix it as well. I recommend taking the rear tire off and checking the undercoating very good as you will be surprised as to the amount of water that gets in from just a little hole. I hope this will help solve your leaks

  • kts0347kts0347 Posts: 44
    Yes, it's a good idea to check for rust penetration as a possible source of leaks. My trunk also leaked and I lay inside while a friend ran a water hose over the deck lid. I discovered that water was coming in UNDER the truck lid weatherstripping. It is glued down at the factory, and over the years the glue had dried out. I bought the correct glue at an auto supply store, pulled off the weatherstrip and re-glued it. This cut down the flow, but I didn't use enough glue to stop it. So I siliconed all around the outer edge of the weatherstrip and it stopped leaking.
    I had another leak at the bottom side edge of my rear window. The sealer there had also dried out. A gob of silicone on a stick to reach the right spot fixed that. And, then there was a leak where the Factory had applied sealer on the metal joints at the tail lights. More silicone. And, there are several screws penetrating the sheet metal. They have sealer under the washers. All dried out. More silicone. And, finally the sunroof tubes. They exit out the rear just behind the wheel wells. They have a slip on connection right at that spot. If it comes disconnected, the water runs right into the trunk. It all heads for the spare tire well. You don't discover it until you have a serious amount of water in there.

    Also, your other problem of the battery being dead is probably because you developed a short under your floor carpets, due to all the water in there. There are a lot of wires running under there, to the power seats, as well as to the rear of the car. Many areas for a water penetration to cause a short. Sounds like the AC condensor was the culprit in your case. But, you still have the electrical problem, as well as a very smelly floor mat. I removed mine (there's a huge amount of foam rubber on the underside that just sponges up the water) in order to clean it. You can get a product at Home Depot/Lowes that will remove the mildew. Check in an earlier post in this thread for the product name. Then let it air dry before replacing. You have to pull the seats to get the carpet out. Kinda heavy job for one person, but do-able.
  • kts0347kts0347 Posts: 44
    They say the only things certain in life are death and taxes.
    The other thing you can be sure of with a Bonneville of that age - it will have leaks. You either fix them, or wear rubber boots. :)
  • Sam, I too had water pooling in all 4 sections of the floor - both driver and passenger. I also had water pooling in the spare tire hold of the trunk but mysteriously, that has stopped.

    For the floor boards, I had two problem areas. I had leaks coming in through both the passenger and driver doors. Also, I had a small leak that was coming in along the windshield wiper arm (driver side) and draining in to the driver floor through the firewall.

    For the doors, water naturally drips inside the door coming in through the window cracks. It is supposed to drain out the bottom. Some of the drips splash against a plastic shield and if sealed properly, the shield deflects the water and it drains out the bottom of the door and outside the car. If the plastic shield isn't sealed properly, the water will leak into the car and get your front and back mats soaked.

    Solution is to pop off the door panel and test it for leaks. You'll need some auto body tools to help you get it off. Take your time and find some directions for removing the panel. Once you get the panel off, test it for leaks by running water from the hose against the outside of the window so that it drains inside the door. You will see how it drips. If the plastic shield is working correctly, the drips will not come through the shield. If it is not working properly, you will need to purchase some caulking at the autoparts store and re-seal it. It is the same caulking they use to seal windshields when they are replaced - very tacky and black - about 3/8" thick.

    Seal up the plastic shield and try running water again to see if the leak stopped.

    Try both doors. I didn' have a leak in the back doors.

    Good luck.
  • lotsofcarslotsofcars Posts: 3
    edited June 2010
    I just recently acquired a 2001 SSEi with all the issues that have been discussed on this forum including the inop windows, locks and passenger mirror. I've torn up the rear and passenger carpets and seat and found tons of water although only yesterday after a huge downpour did it show up above the carpet. How can yo even get at the rear drain tubes of the sunroof? and must you remove the headliner? It is humid and the A/C has been running heavy and I see some have blamed that drain tube. Seems like four to five different solutions, how do you know which to tackle? Everyone of them are huge jobs. Is this a job for a body shop?
    Please imidazol97, send me the info you have graciously shared. I'll try to get something fixed but I'm starting to think this car is going on the auction block soon, what a nightmare and it sounds like a very common problem in all years/models too. We have looked for any wiring, terminals, etc. that might be leading to the electrical shorts and can't find anything that would be the culprit. Is there a specific location (pic would help) that can be pinpointed for fixing the window/lock problem?
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,311
    edited June 2010
    >window/lock problem?'

    You didn't specify but I assume the driver's door works for power windows and locks, but the other three don't work. They communicate with the module in the driver's door via a brown wire that meets three other brown wires under the driver's seat, and it might be under the floor mat. I'll look for a picture if I can find a link. They are coupled with a press fitting and corrosion occurs--especially if your car hs become Noah's Ark!

    Send an email to the address you see when you click on my user name at the top of this message, so I'll have an email address for you. Your CarSpace user email doesn't seem to be working yet.

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

  • 2001 SSEI w/ sunroof and all same the issues that have been discussed on this forum. The driver's side floor is soaked. My driver's door power lock, mirror and window works, but none of the other power windows, mirror or locks work even from their own doors. I currently have the seat removed and the carpet up on the driver's side front and rear. I will be testing with a hose for leaks, but I am more concerned about repairing the windows since the rear driver's side window is currently in the down position. I at least need to get the window up, so I don't need to cover it with a tarp every night. Can anyone specifically provide information on how to fix the wiring, or could it start working properly once it's dried out?
  • kts0347kts0347 Posts: 44
    Hello Cyberbrat,

    Your post dates back some, but nobody seemed to answer your question. By now you may well know the answer from DIY discovery. But here goes.
    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, as you say.
    Two others lead rearward and drain down the C Pillar and lead off into the trunk and exit into the trailing edge of the fender well. The drain ends again are invisible under the car.
    The drain tubes push fit onto the large plastic tray that catches the rainwater coming through the sunroof opening. Pontiac's engineering intent was not to attempt 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 under the window (and above the headliner) 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 are made in several sections press fitting together. These sections can separate (and do, if you attempt to clear the tubes using compressed air). The sites where the sections come together are in extremely awkward locations, and require cutting of insulation etc. to find. The third leakage problem is the tubes tend to clog up with debris. When that occurs the catch basin in the roof simply overflows, and gravity takes it to the floor via the roof pillars and then following the hard trim. I have cleaned my tubes two years ago, and they are clogged again.

    If anyone has a simple method of cleaning the tubes without blowing them apart with an air hose, please add it now.

    That said, the sunroof isn't the only source of leaks in a Bonneville. The doors themselves are sources of leaks. The door design uses a sheet of polyethylene adhered to the door inner sheet metal to keep moisture out. Over time, the mastic used to adhere the sheet simply releases, and water flows into the car through the doors. The solution is to remove the door inners, and re-adhere the polyethylene sheet with new mastic or a high quality sealant.

    Then there is the air conditioner drain tube. It also plugs up. When it does, all the air conditioning condensate has to go somewhere, so it flows right onto your carpet. Fortunately, the AC drain hose can be seen under the car, and a coat hanger will unclog it.

    And, owners also report sundry leaks from windows and cowl sheet metal joints that had factory waterproofing applied to seal them. This are tedious to locate but fortunately are not too common. Sunroof, Doors and AC are the usual culprits.
  • rocky74rocky74 Posts: 15
    I am no mechanic by any stretch of the imagination, but you or your mechanic should take a look at the wires to see what they look like. What I was told by the mechanic at the dealer's was that the wires were corroded and they had to remove the corroded parts and replace it with new wire. Once that was done, I could open all four windows (one rear window had been broken for a while), and I stopped getting most of my idiot lights turned on, although the security light tends to stay on again.

    We had horrible rains today, and a few days ago, and mysteriously there was no leakage into my car. The only thing I did differently was move some stuff around in the trunk, so I'm thinking that the water in my car leaked in through the trunk somehow.
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