Pontiac Grand Prix Water Leak

eric227eric227 Member Posts: 8
I have a '98 Grand Prix that started leaking water to the passenger floorboard during severe rainstorms. This happened about a year ago. I took it to the dealer and they checked the A/C and found nothing plugged up. At the time the molding around the windshield on the passenger was loose. However, that didn't seem to be the cause either. They thought it might be a cowl leak and told me to take it an auto body/glass place. The auto body/glass place looked at it and said it wasn't a cowl leak but that it appeared a was missing near the vents for defrosting (underneath the wipers). When a hose was run over this portion of the car water would run in on the passenger side footrest. The body shop even demonstrated this for me with the carpet pulled up. They said I should go back to the dealer and ask about this apparent missing piece. Went back to the dealer and they said nothing was supposed to be there. They even showed me a new Grand Prix to compare to.

I ended up going back to the body shop and paying $300 for them to make something to run the water another way by the vents and I haven't had a problem since. Wasn't happy, but it was raining a couple of times a week and I was tired of bailing out my car.


  • ndclarkndclark Member Posts: 3
    I also have encountered the same problem with my 1998 Pontiac Grand Prix. When it rains really hard the passenger side floorboard will fill with water. I was in the car when it was raining hard and the water was draining directly under the dashboard from the top of the floorboard. Its lovely to have wet wires and im waiting for a major electrical problem soon. If anyone has an idea about what this may be from please help a guy out. I heard it could be from the heater core but Im not sure if that makes sense? Thanks!
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    Sounds like the fresh air vent drains (under your windshield wipers)are clogged. These drains allow water to escape into drains that usually exit just back of the front wheels.

    If you carefully poured just a teacup of water down the vent grilles, you should see water exiting under the car. If you don't, the drains are clogged with bio-matter and the water rises and rises until it spills into the car itself behind the dash.
  • condorcondor Member Posts: 2
    Same problem here (2000 Pontiac Grand Prix). Easy repair. There is a poorly secured waterguard under the plastic lip which loosly seals agains the length of the windshield. I found the issue, placed the waterguard back over the steel lip (which is all found under the black plastic. For good measure, I laid a bead of silacone between the plastic and winshield along the passenger side. Without the waterguard in place, water is channeled directly into the A/C air intake. That drains into the fan motor casing which eventually overflows onto the floor board. I found this out by placing a garden hose on my windshield and removing my glove compartment door. Haven't had a leak since.
  • rwarner1rwarner1 Member Posts: 1
    Same issue I'm currently dealing with. What are the steps for removal.
    Remove Wiper.
    Remove Plastic cover?
    Then what?
    Is the waterguard or seal visible at this point?
    Any help is appreciated. Right now I have to change cars with my wife when it rains. She can park in a parking garage at work, I can't.

    Please reply also if possible to [email protected]
    RW">link title
  • john59john59 Member Posts: 1
    I have a 99 Grand Prix. I had to replace my windshield over a year ago. Ever since, my floor boards on both the driver and passenger sides are soaked after a heavy rain. Could this be due to the windshield replacement? Maybe glass repairman's fault?
  • melodyjmelodyj Member Posts: 1
    I bought my car in Jan. 06. 1998 Grand Prix. Every time it rains my passenger side floorboard has 1-2 inches of water. No the ac drainage pipe (whatever it is) is not clogged. I had some wires short out 3 days ago and now my ac, radio and display lights will not work. My brother pulled out glove box for a look and found a box, audio amplifier that looks fried, could this be my problem causing the ac, radio and display lights not work. I need help, no one seems to know anything about this problem here. And how do I stop the Leak???!!!???
  • mostro186mostro186 Member Posts: 2
    Meldoy, sister! I had the same problem with my '98 GT! Thought it was a crack or leak on windshield. It was the water regulator inside the bottom of the windshield! It just needed to be set back in place. Have someone remove the plastic plate holding your windshield on (Lower). It's rubber and easy to fix. Don't pay someone to do it you can do it yourself grilfriend!! I HOPE this is your solution! I almost know it is! :) Marie
  • naseem641naseem641 Member Posts: 6
    I have the same exact problem with my car... i poured water down the vent grills and the water came ou the bottom like its supposed to... now i jus took it to a mechanic and he said they have to take off the whole entire dashboard and do something with the water heater... i do not understand how all this water can come from a water heater? They want to charge me 325$ and id rather get a simple solution and do it myself.
  • escambiaguyescambiaguy Member Posts: 35
    I have a 99 Grand Prix GT and have the same problem. One day after a heavy rain I was driving and when I made a lefthand turn water started gushing from underneath the dash. I could hear it going through the a/c fan motor. The dealership said it was the a/c drain line and charged me to unstop it. Needless to say, it messed up my blower and resistor, which were easy fixes. The car also now has a musty smell. I still have my doubts if this problem is really solved. I never drive it in the rain anymore. I decided to sell it because i'm tired of worrying with it.
  • guestguest Member Posts: 770
    Have you had any luck finding a solution to this problem?
  • naseem641naseem641 Member Posts: 6
    yes... a temp. one... keep my car in my garage when it rains lol.... but other than that, im still clueless
  • stan60stan60 Member Posts: 5
    The water is leaking between the plastic that sits on the windshield behind the wiper blades. Behind the plastic is a foam gasket that deteriorates and the water runs down into the heater fan motor and overflows onto the floor. Buy a tube of black silicone and run a bead across the plastic where it meets the windshield if you do not want to take the whole thing apart. It was a problem with my wifes car until I took it all apart to find the problem. Okay now. Stan :)
  • debmc03debmc03 Member Posts: 2
    I tried using some old weather-stripping I had on hand,but still had some leakage.Yesterday I used some clear RTV silicone sealant adhesive,and ran it across most of the windshield area you speak of.It rained cats n dogs today,but I still have a small amount of water seeping in.I dropped the glove box,and can stick my hand out the rubber door behind there,and there was no water standing there,so now I am stumped as to where exactly it is coming in at.I will put more sealant around the edges if it ever stops raining.I just got the car for new teen driver,and seems we have had more trouble than its been worth.The leak fried the blower fan relay (i think),so now the fan only works on #5,but hate to replace it and have it get ruined too!I am worried the water will ruin the wires,radio,etc.Winter is coming and I NEED to resolve this!
    Also,how does one clear the things that run from front to back on each side of top of car? I dont know what they are called,but are tiny drain things.I think I heard someone say once that dealership maintenance people cleared theirs with a long pipe-cleaner thing,and ran it the length of the pipe.Just taking wild guesses now...........
    Any more help and advice would be appreciated.reply on here or contact me by email if anyone has any words of wisdom Thanks
  • brightguybrightguy Member Posts: 5
    New ,Used G.P.owner,I have a good idea what causes this,after looking at the way they did that being an contractor and not a mechanic,Under The car the a/c Drain pops out horizontily With that cheap tee down spout,If that down spout is loose or is not there,water would simply travel back onthat plastic nub{which pops out from inside{Walks up the pipe back into the car,I connected a 1/2 plastic pipe to the inside and routed the water drip to a better place , instead washing the dirt of thecarrage.
  • jd1965jd1965 Member Posts: 1
    Hello Stan

    I hope you've had some success solving your problem. I recently purchased a 1999 Grand Prix and have not yet experienced any of the "leaking" issues that have been described by you and the others. However, I suspect there may be a similar problem with my vehicle because all of a sudden my heater motor will only operate on #5 (high). Like you, I don't want to replace anything until I know for sure what the problem is. Winter is already in full swing where I live so any help you can provide would be greatly appreciated.


  • brybrybrybry Member Posts: 25
    I followed ndclark message #5 instructions. I fixed the problem also and it is simple. Leave the wipers in the vertical position on your windshield (no need to remove it). Lift the hood. On the right side or passenger side you'll see a plastic cover with a grated vent on it, this is removed by unscrewing or prying on the plastic clips holding it down(2 of them)plainly visible. Remove your washer fluid hoses that are just clipped on and can be easily replaced. Remove the cowl and you will now see your blower motor down below. This is where the water is getting into your car. On my car the sponge water channel about 2 feet long had almost fallen off. I put a bead of silicone in the slot where the sponge slides onto the steel lip to hold it on so it won't fall off later. The bulk of the sponge seal points upward. Take note of its orientation and location before you remove it if it is still on the lip. This seal directs water to the proper drains away from the blower motor. It took me about fifteen minutes to correct. Hope this helps,good luck.
  • mooky_mikemooky_mike Member Posts: 1
    (2000 G.P-S.E) Just found this site...wish I woul have found it earlier.Have had tones of the same problems. As for the water leak I have a major one as well I get a swimming pool on the passangers side floor.Have had the heater motor and resister replaced 2 times.Getting bad again so I'am getting 2007 GXP next month...I still love My grand prix
  • appjej123appjej123 Member Posts: 9
    I am glad I found you guys!!!!!!!!!!!!

    I have a 2000 GP GT with 79k on it.

    I have been experiencing all the problems regarding the water leak (for a year or so) and the problems with the blower fan/resister board/daytime running lights.

    I shared this information with my mechanic, who was working his thru the problems to this.

    He's going to finish today, with the help of this info, and hopefully be able to keep the bill down a little.

    My car has had one other "sporadic" issue. The car would occasionally stall, typically during SLOW, RIGHT turns. I'm hoping that may be ignition related as well.
  • craig32craig32 Member Posts: 30
    Anyone had any problems with 200 GP'S, SE models??
  • norris65norris65 Member Posts: 1
    Hello, my 2000 Grand Prix has had a small too. My friend has a 2002, his car had real flooding. We had replaced the resistor packs and blower motors, last fall. (Funny my original blower is back in now, dry out and a little WD40 & it was good to go)

    Note the rubber guards and seals were tight and in position, on my 2000 Grand Prix.

    Today we reattached my friends rubber guard and sealed it though. Then we vacuumed out both cars the blower motor areas, reversed the shop vac and blew the vents out.

    Replaced Cabin Air Filters, then installed home made water deflects. Air conditioner worked fine today.

    These deflectors will put and end to the leaks. ;)
  • cobbler63cobbler63 Member Posts: 1
    Trunk Leaks seal has no cracks or tears.
    Taken to several dealer and they can not figure out why I have water standing in my truck. Any suggestions.
  • dtrombleydtrombley Member Posts: 3
    I have a 2005 Grand Prix and my floorboards passenger front and rear were soaked with rain water. It took my 2 1/2 hours to vac all the water. Just this morning I took it to the dealer. He told me the cowl was leaking soaking the floor and the trunk . He also said it would coast 310.00 to fix it. Iam pisst because I bought an extended warranty and they said it wont cover the leak. So I asked why did I buy this warranty . They said to cover the car but it wint cover the leak. I hate car dealers.So now it is being fixed for 310.00
  • appjej123appjej123 Member Posts: 9
    That is awful! They KNOW it's a design flaw. It's been happening since the 90's! Mine is a 2000. I had to have my windshield replaced due to a crack and I'm hoping that since I told them and asked them to that they added silicone or something to keep the seal.
  • gtprixgtprix Member Posts: 1
    I had a similar problem, it was the tail fin silicone around the bolts. There are six nuts attaching the fin to the trunk lid (bolts are embedded in fin). The silicone around the bolts had deteriated and was allowing water in. I cleaned up the area, apply a health layer of black silicone and no more leak. Hope that helps. :shades:

    My problem with leaks is when I run the AC. I it hasn't rained in days and yesterday I was blasting the AC on a long ride and water starting pouring out of the passenger side floor vents after an hour of running it. It has to be the AC somehow I'm just not familiar enough with where the water run off from the AC is at.
  • henriejohenriejo Member Posts: 2
    I have a major water leak in my 2004 grand prix. It first happened around 2005 when it rained during hurricane Katrina. I didn't really think anything of it. Thought maybe the water in the backseat could have wasted because we had water in the cooler for our road trip when we were getting out of town.
    Well, we moved to Oklahoma, and for this year it has been very rainy and stormy. Water has been getting in the car nonstop. I finally decided I had enough when water was stagnant on the passenger rear floor board and took it to the shop (pontiac dealership)last week. My insurance covered it because they said it could be water damaged.
    So the car sat up there 10 days. No solution. No problem. No one knew what was wrong. The insurance decided to replace the carpet that was molded by the rains without knowing what was wrong. At this point, I became really upset. Covering up the problem without fixing it. I also forgot to mention that water had gotten into the car 2 months prior during a heavy rain and knocked the a/c out. The a/c was fully functioning fine until that night. Well, the insurance decided it was not the water that knocked it out, it was a mechanical issue and my warranty covered it. So back to the story. I called the insurance and went off on them asking them how can give an estimate, release the car and try to cover up the problem without knowing the cause. This was 2 days before I picked up my car. They said they needed to see if they could find out what the problem was first before they could do anything else.
    I decided when Thursday rolled around, I would just pick it up. It better be dry and if it happened again, insurance was going to pay. I was going to find someone that could diagnose the problem. There was still no resolution to this ongoing issue. Thusday was accompanied by a heavy rain. Friday rolls around. I am at work at 6:00 PM. Mind you it is sunny, and nice. I haven't felt the carpet since the rain, so I decided to. Front driver side. Dry. Front passenger side. Dry. Back driver side. Dry. Back passenger side. Wet. Wait a minute? Wet....So the water has something to do with something near rear passenger that is causing water to build up in the car. I called the insurance back upset. I told them that water is coming in the car still, and they need to fix this problem. They are obviously missing something. Well, the guy who handles my claims is off. Great. He won't be in until Monday. I told them well, I need this fixed now. I was advised I can take my car to a shop and be reimbursed for any out of pocket expenses. So I will take the car in immediately as soon as a shop opens while this is fresh. I also started researching on the internet to see if there are people that have this problem and low and behold....A lot of people seem to be having a problem with leaks. I was really surprised because it was a shot in the dark. I just want to know if anyone knows what is causing the water to first enter the rear passenger side? What could be causing this issue where water is getting into my car? :cry:
  • nategreynategrey Member Posts: 2
    I have a 1998 pontiac grand prix gtp coupe and my passenger side floor gets flooded everytime it rains.

    Temporary solutions seem to be that when I park the car DOWNHILL, water doesn't seem to get into the passenger side floor. When parking straight or even uphill, that's when the water starts coming in.

    I'm going to try some of the suggestions on this forum to see if I can fix it completely.
  • henriejohenriejo Member Posts: 2
    The body shop finally found out what was wrong with the car. They said the seal on the windshield was bumpy and was letting water in. They also said there was a loose cowl, which was diverting water into the car. It was a good soaking rain the day after I picked it up, and I checked the car. No leaks. Clean as a whistle. I am very happy this was finally solved. They had the car for almost two weeks trying to figure out what was wrong with it. I was so worried it would not be solved. I would suggest looking to see if there is a problem with the cowl which probably has something to do with the majority of all grand prix leaks. I saw there was a recall about it on pontiac website. Also try looking at the windshield to make sure it is sealed all the way. These problems could be an issue since your leak is coming in the same side mine was.
  • bigskidoggbigskidogg Member Posts: 8
    My 2000 gran prix has been leaking water in the front passenger side also, i fixed the rubber seal as stated in another post and this solved the rain problem but now the air conditioner is leaking into the same area just as bad as when it rains, i know its the a/c because it leaked on a sunny hot day with no rain, i read of a fix on an a/c drain line in another message, does someone know the exact way to unplug the line? any help is greatly appreciated.
  • lpattersonlpatterson Member Posts: 1
    This worked for me but I would add. You might want to go to Auto Zone and buy some 5/16" nylon rivets, 961-060 by Dorman before you pry them out, because they are worthless after you pry them out. Also there is a another cap on my 2001 with a flat line that screws out which is reusable. It's also advisable to pry the rivets out from under the hood so you don't damage your windshield, I used a nail puller.
  • kristy346kristy346 Member Posts: 1
    What is a COWL and where is it located?????
  • netman1netman1 Member Posts: 1
    I am having the same problem. Did you ever isolate the cause of your leak on the back passenger floorboard?
  • appjej123appjej123 Member Posts: 9
    No, I sure didn't. Even with the new windshield it happened again. I was able to find the spot where it came in, way up under the dash, you'll find an opening you can put your finger through. Why it's there I don't know.
    I actually sold my car a couple of weeks ago.
    Good Luck!
  • dtrombleydtrombley Member Posts: 3
    Hey just wanted to reply to you.
    I have not had a problem with that spot again .
    I took my car to the dealer they found a leak in the cowl .They also wanted to charge me $ 325.00 to fix it even though it was still under warranty. and still is
    I plan to traed it in this spring
    thanks fboy
  • jamijanjamijan Member Posts: 2
    I am also interested in unplugging the a/c drain line. Does anyone have ideas? I have a 2001 Grand Prix. The other tips have been helpful but my car is also getting wet on the front passenger side floor on warm dry days when I use my air conditioner. The blower is leaking water. Any help would be greatly appreciated. Thanks.
  • bigskidoggbigskidogg Member Posts: 8
    I was finally able to get this issue solve, i found the rubber strip that is under the plastic piece by the windshield and sure enough it was off so i glued it on with some rubber cement. fixed the rain problem but still had the ac condensation flowing back up because the drainage tube was clogged. couldnt find it on my own, took it to a garage that my father recommended and he put it up on the lift and showed me where it was at and stuck a small phillips screwdriver or and small thin metal object to stick up the tube and unplug it. it took like 2 seconds. it is hard to see the tube i wouldnt have found it on my own but on a lift it was easier to locate . it came down right around where the engine and tranny are, pretty much directly inline with the firewall but it was a very small tube like an 1/8 inch or something. the end of it was greenish because of the mold and gunk so it really didnt look like it could have been the tube but he stuck the screwdriver about 1 inch or so up into it and all of the water which wasnt really alot came right out and it solved the problem. you might be able to find it if you put it up on jack stands and have a little room to look around, that was my problem, i couldnt really see it from just looking underneath. but once it was on the lift it was definitely findable. good luck. i believe this will solve your problem.
  • jamijanjamijan Member Posts: 2
    Thanks bigskidogg. I found the drain on plugged it and the problem is sloved. I found the drain looking in from the top. In my 2001 Grand Prix under the dash on the passenger side, I had removed the cover over the blower, held in place by three anchors. I followed the pipe coming out of the blower into the firewall. Then I looked under the hood where this pipe should come out. There was the drain. a short elbow coming out and pointing down. It was difficult to reach but I was able to unplug it with a piece of stiff wire. My car has been dry since then. Thanks.
  • taylor981taylor981 Member Posts: 1
    I have an 04 Grand Prix and lately I have noticed that whenever I get home from work or a drive anywhere, there is a nice puddle of water underneath the car where the A/C would normally drain out, except I haven't used the A/C. I've actually had the heater on. The puddle keeps getting bigger and bigger each time. This morning when I started the car and left for work, there was already a puddle of water in the driveway after the car running for only maybe 5 minutes. I popped the hood last night and found the water was coming out of a drain elbow that looks like it's going into the firewall. Why is my car leaking so much water on the ground???? I've never had this happen with any other car I've owned.
  • jlgiffordjlgifford Member Posts: 1
    It doesn't get any better in 2006, my back passenger side foot well is a nice puddle and my car stinks like mold. Living in Florida, I can rest assured there is mold all over the car and it is now a health hazard. I would like to know why, if this has been an ongoing problem, hasn't GM done anything about it?
  • nategreynategrey Member Posts: 2
    GM doesn't do anything about it because people are still buying it.
    Seems like lack of dilligence on their end as a means of cost saving. They're actually saving at the cost of their customers.
  • rjcoynerjcoyne Member Posts: 1
    I have a 2004 Grand Prix and, like all of you, my passenger side floors and air conditioner have water leaking problems. My car also smells like mold and has since i bought it. When i speed up or go over a speed bump I can hear water sloshing around in engine/dashboard. The air-conditioned air smells terrible. I got my windshield fixed over a year ago and since then, the water leak on the floor has been minimal, but the air conditioner problem is bad. I'm taking it to the dealer tomorrow after reading this thread
  • larrybohlarryboh Member Posts: 1
    I have a Grnd Prix that is doing exactly the same thing. Wet floor on the passenger side and a very annoying sloshing sound in engine/dashboard. Were you able to get your car fixed and if so can you share what was wrong?
  • dtrombleydtrombley Member Posts: 3
    well it was the cowl that was leaking .after i got it fixed i traded it in
    and im glad i did
  • ralkaralka Member Posts: 72
    sounds like water in the hvac case through the vent
  • lmcilhenneylmcilhenney Member Posts: 1
    My car is leaking water when it rains, it's a 2006 Pontiac Grand Prix GXP, 38,000 miles. The interior is ruined from the last rain storm and I am told by the dealer that this is my problem. It's probably a clogged drain line from the moonroof. They have a water guy on the schedule for Tuesdays, so if they know there is a problem,why isn't this recalled? My car is ruined and it is my responsibility.Even if i purchased an extended warranty water leaks are not covered. So I have a car GM certified vehicle with less than 38k miles, that has significant water damage and they are not responsible for any of it. I wash my car faithfully, and was told it's probably pine needles or anything clogging the drain line, but it's not they're problem. The car is ruined. Any suggestions?
  • zach10hzach10h Member Posts: 1
    I have the same problem, only I have a 2002 coupe and the water leaks onto the passenger side floorboard. I have determined that the problem is coming from faulty drainage in the door. Every car is designed to allow water to flow down the side windows and let some flow into the door itself and drain out the bottom. This design is what allows the window to be rolled up or down, however, in my case, and maybe yours, too much water enters the door from the space between the window and the seal on the bottom of the window. The excess water does not drain properly and backs up into the door, forcing it out into the car. It has not suffered water damage yet because I promptly dry it when it leaks, until I find a permanent fix, I will just stuff a towel between the bottom of the door and the interior of the car to prevent floorboard flooding.
  • 426cudaman426cudaman Member Posts: 2
    I also had the same problem and spent over two thousand dollars before i found out what the problem was. All Pontiac grand prix from 1999-2009 that leak water on passenger floor is from the following: The front cowl panel, [Where windshield wipers are] Has a air box inside the panel, That when built has a two piece construction that is sandwiched together at factory, and over time, summer heat, Icy winters etc, dries out and allows water to get into air box and drip out below dash on passenger side. To fix: Remove wiper arms, remove cowl screen, and you will notice a box looking square on passenger side, Clean out in and around box opening top. Must be clean and dry. Next use ether urethane windshield sealant, or silicone water proof sealer. reseal all the way around box , [Where metal body meets air box.] Make sure to re seal all the way around air box and let dry overnite. You can buy ether sealants at your local automotive parts co.
  • 426cudaman426cudaman Member Posts: 2
    I also had the same problem and spent over two thousand dollars before i found out what the problem was. All Pontiac grand prix from 1999-2009 that leak water on passenger floor is from the following: The front cowl panel, [Where windshield wipers are] Has a air box inside the panel, That when built has a two piece construction that is sandwiched together at factory, and over time, summer heat, Icy winters etc, dries out and allows water to get into air box and drip out below dash on passenger side. To fix: Remove wiper arms, remove cowl screen, and you will notice a box looking square on passenger side, Clean out in and around box opening top. Must be clean and dry. Next use ether urethane windshield sealant, or silicone water proof sealer. reseal all the way around box , [Where metal body meets air box.] Make sure to re seal all the way around air box and let dry overnite. You can buy ether sealants at your local automotive parts co.
  • tad7tad7 Member Posts: 1
    Please let me know if this is something that you have fixed yourself or paid the Dealer to resolve. I have a 2006 GXP [40k miles] that is leaking from the MoonRoof as described in the previous post. There are stains developing on the interior roof (the cloth material just above the top of the door). Hopefully, I can clean out the MoonRoof drainage component myself. Or find out if the Dealer can fix this common issue most expeditiously ! Thanks :mad:
  • gmcustsvcgmcustsvc Member Posts: 4,252
    Please keep me posted on your progress. If you have any questions or concerns before or after you take your vehicle to the dealer, feel free to send me a personal message. Thank you!
    Joey, GM Customer Service
  • jpfjpf Member Posts: 496
    Contact a lawyer. Good luck.
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