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Fred Parmenter 03-05-2011 10:31 AM

Z3 Leaky Roof
Fastwoman contributed a wonderful posting in this forum on figuring out the cause for her Z3's leaky roof, and providing some great pictures and text of how she fixed the problem. My Z3 also leaks (it has the hardtop on). I thought I might post my experiences so far with trying to fix the leak. Actually two leaks, one on either side near the top of A-pillars.

I took off the hardtop and all gaskets seemed clean, pliable, and in good shape. I poured water into the windshield's gasket's crevice and sure enough, just like Fastwoman said, the water flowed down the crevice, disappeared, and then appeared as a small puddle under the car. Fastwoman said there is a water channel in the A-pillar which is supposed to do this, and it seemed to work fine.

I did find the triangular "plug" Fastwoman talked about, but it didn't seem loose. I pushed it and pulled it a little, but didn't see it separate from its housing. For Fastwoman the "plug" was loose and she added some silicone or glue to reseal it. But in my case I didn't see any water coming out the "plug."

Not knowing what else to do I put the hardtop back on and did a hose test on the car. My driveway is at an angle. I first parked the car with the front higher than the the rear, gave the window area a real good shower from the hose, but didn't see anything dripping.

I next reversed the car, so now the hood was pointing down hill. Sprayed again and now saw water dripping inside. Still, I had to spray a lot water before seeing the dripping.

Next I parked the car across the driveway (perpendicular to the drive way) so it was level (front-to-back) but angled down driver's side-to-passenger side. Then I repeated the hose test and this time water right away started dripping inside.

I put the car back in the garage (which is level). The next morning I dumped 2 cups of water from a Pyrex measure on the windshield area near the A-pillar. No leak. I poured another 2 cups of water. No leak. I filled a 3 quart sauce pan of water and dumped the whole thing. Leak! Dripping inside the car! So right away I opened the car door and it seemed to be leaking from the junction where the windshield's gasket butts up against the hardtop's gasket. This is right where the "plug" is that Fastwoman refers to. I pushed my finger in a bit to push apart these two gaskets but didn't see anything conclusive. Of course by this point the water was no longer dripping.

I suppose the water could have been coming out the "plug" Fastwoman wrote about. I'm not sure what to do next. Maybe tomorrow I'll take the hardtop off again and try to pour and pour water down the windshield and hope to see it come out the "plug."

By the way, it leaks the same way on the other side. I recently bought the Z3 and it came with the hardtop on it. I'm not supposed to raise the soft top until the weather warms, so I don't know yet if it will leak when I put up the soft top.

Opinions sought and appreciated.

Racerman27410 03-05-2011 03:54 PM

the plugs may appear to be tight but trust me they are not watertight.

i grabbed mine with some needle nose pliers to remove it.... it has a long trunk on it.

smeared some black silicon sealer on it and shoved it back in place.... no more leaks from the hard top or the soft top.

Fred Parmenter 03-07-2011 01:10 PM

Racerman27410's post appears to be correct. When I took off the hardtop again I could see space around the "plug." I was quite excited by this. So I got out some RTV silicone and pushed the nozzle of the silicone's tube in and around the "plug." I wish I had read Racerman27410 's post better and realized I was supposed to take the "plug" out, fill the hole with silicone, and then put the "plug" back. Anyway I thought I was just supposed to push the silicone in around the "plug."

I let the car sit for about 20 hours or so to cure the silicone before I dumped a 3 quart saucepan full of water on the area. No leak. At this point I was cautiously optimistic, but...

Later I took the car outside and gave the driver side a good hose soaking and water started coming in the driver's side. (I gave it quite a long extended soaking however.) Maybe in most rain storms it will be OK.

A long soaking on the passenger's side did not result in any leaking.

I am somewhat mechanical, but no where near like the others on this forum. Maybe I should have taken it to a dealer. I guess I still could. Maybe I'll just see how bad it is in a rain storm. And I guess I could always hope when I start using the soft top that the problem will go away.

pvtpilot91 03-07-2011 02:11 PM

I had the dealer replace the gaskets, which cost a whole lot and my soft top still leaked. I got out some silicone grease for laboratory stopcocks and have been lightly coating the rubber seals annually ever since with great no leaking results! What an inexpensive what to go:thumbup:

Fred Parmenter 03-07-2011 02:42 PM

pvtpilot91, when you said you "lightly coated the rubber seals" what seals were you referring to? Did you mean you lightly coated all the gaskets or weatherstripping which runs along the windshield and soft top, or did you put the silicone only at certain places?

Racerman27410 03-07-2011 02:59 PM

after removing the plug you dont want to fill the hole with silicon.... there are some intricate pathways built into the mess that channel the water to where it needs to go. blocking these areas with silicon is not going to help your situation.

after removing the plug just smear a coating of sealant onto the rear portion of the plug and shove the entire thing back in place... being careful of how it is supposed to be oriented inside the channel.

then just wipe off the excess sealant that gets left exposed after re inserting the plug.

the way you did it you have no idea where or how much silicon you have blocking the inside of the channel.

I would pull the plugs, clear everything out and try again.

pvtpilot91 03-07-2011 03:20 PM


Originally Posted by Fred Parmenter (Post 5900142)
pvtpilot91, when you said you "lightly coated the rubber seals" what seals were you referring to? Did you mean you lightly coated all the gaskets or weatherstripping which runs along the windshield and soft top, or did you put the silicone only at certain places?

Hi Fred, I meant that I coated all the weatherstripping, including where the convertible top closes against the top of the windshield frame. I also coated the "breaks" in the weatherstripping which can be seen as the top is lowered about halfway down. these allow the weatherstripping to fold along the metal frame on the convertible top. Steve

matney 03-10-2011 07:06 AM

same problem
Hi there i had the same problem on my drivers side with hardtop fitted, used to leak with heavy downpours.
Managed to fix it now though!
I also didnt have any leaks through the plug but took it out and re-sealed it , still leaked.
What i noticed though that when lots of water was put over the area the water would overflow the small lip that is present at the end of the a pillar and then run into the car (when i took the hard top off) This didnt happen on the passenger side as the lip seemed to force the overflowing water down the outside of the car over the small 1/4 front window.
My next step was to build up the lip on the drivers side slightly with a bit of silicone only by about 1/2 cm but hey presto when there was too much water for the two leak holes to manage, the excess water went down the outside of the car.
Hardtop back on and hey presto a dry seat.
May not be the same for your car but worked for me.

Fred Parmenter 03-10-2011 01:16 PM

Thanks for the input

Thanks for sharing your solution of using silicone to build up that little lip. I have seen that lip protruding toward the rear of the car from the A-pillar and couldn't figure out its purpose. Next time I have the hardtop off I'll try the same procedure of slowly pouring water down the roof and see if it follows that lip and then into the car. I'm not exactly sure what portion of the lip you were building up with the silicone, but maybe it will become obvious when I watch it drip.

That was also interesting that you only had the problem on one side of the car. The good side's lip probably gave you an idea of what the leaky side's lip should look like. In my case both sides leak.

Fred Parmenter 03-13-2011 02:36 PM

Thanks again - at least partial success
Thanks again for all the help. We had a bit of a strong rain here a couple of days ago and I left the car outside. It fared quite well. Later in the day I did see some drops of water on the drive side A-pillar, but nothing on the passenger side. Eventually when the car gets dirty enough I may take it into a car wash just to really test it.

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