Gap between Rubber Windshield Seal & Body

[david914]

First of all, a big "Hell yeah!" to Randy B!

Now, lemme pose another question to you guys. As stated earlier, I've got a new windshield (Sigla) and new OEM seal purchased from our host.

Shortly after having the windshield and seal installed by my local installer, it started leaking when it rains. It pools in the lower corners between the seal and the glass enough that water seeps in between the glass and the seal (not between the body and the seal). My question is should there be any sealant applied in the groove that the glass resides in, or does the "no sealant required" apply here as well?

[randywebb]

I'd make them do it over & do it right.


But yes, you can get guys to come out and inject sealant into the window channel on any car. It's a cheap 'fix.' But I've seen people here object to it as not a very good fix...

[david914]

Is it possible that "tweaking" the corners as described previously will remedy the leak?

[porsche930dude]

theres only one way to find out

[Randy Blaylock]

It's very typical for water to pool on top of the seal and glass in the lower corners, and not cause for concern in and of itself. It's hard to say whether the water is getting in there, or finding it's way by the seal further up and collecting in the body until it seeps over the flange. Water does move around in very interesting ways that aren't always easy to predict.

A caveat to all of this, I think it goes without saying that the seal has to be in decent servicable condition, without UV checking and what not.

As has been described earlier, the seal has an "H" shape to it. Actually, there is a third channel that's very thin and oriented perpendicularly to the others, where the aluminum trim inserts. If you were to cut a section out of the rubber seal and view it on profile you could see this more easily.

That's not really material to this issue beyond knowing that the thickness of the part of the trim that inserts into the rubber seal adds to the sealing component of the assembly. It does this by contributing to the shape of the seal in the same way that adding a shim to any gap causes the gap to spread proportionally to the thickness of the shim, along with a corresponding change in shape of whatever the shim is being placed. It also acts almost like a keystone in an arch, shaping the edges of the seal where they contact the glass and chassis to help the sealing quality. So it's important to use the trim as part of the assembly or you will never achieve a seal.

For discussion sake, just ignore all that and be sure to use the aluminum trim if you expect a seal.

So let's just say that one side of the "H" wraps around the glass, and the other wraps around a flange that's formed into the sheet metal of the chassis within the windshield opening. This flange is what the seal is worked over with string when installing a windshield. Ordinarily, when installing the glass, the seal itself is installed around the perimeter of the glass, and the aluminum trim is inserted into the seal in the thin opening. This assembly is then laid into the opening and stringed into place, leaving the seal surrounding the glass tightly, and the assembly somewhat loose in the opening, typically with gaps at the corners.

An important element to consider is that the tolerance between the glass and the opening is such that if a person were to lay the glass alone with no seal in the chassis opening, it would simply fall in. There is that much extra space for the seal to make up and move around in.

Back to the initial installation. So the assembly is in place in the chassis, and the seal is now tightly wrapped around the glass as a function of stringing it in. There are almost always gaps around the chassis opening where the outside edge of the seal isn't overlapping the edge of the opening, most pronounced in the upper corners usually.

The idea is to work the seal so that it rides partly on the glass, and partly on the chassis. This means that the seal should be pushed out in all directions, especially in the corners, but also along the straighter areas, so that the outer edge of the seal overlaps the chassis by several mm at least. The corners usually need some shaping to assume the tight radius of the corners, while the longer edges of the top, bottom and sides can be worked by hand pretty easily. It's important to note, and should go without saying, that the surface where the seal lays needs to be smooth with no wax build up, paint overspray edges, rust bubbles etc... You don't need to worry about overdoing it, I don't think it's possible to work the seal out away from the edge of the glass to the point where a gap will be opened up.

This is the important part. When the outer lip is firmly riding on the chassis, the weight of the glass, in conjunction with the aluminum trim piece, causes the inner edge of the seal to press firmly on the glass surface, and the outer edge to ride on the chassis, sealing rubber against glass and paint to exclude water.

If the outer edge of the seal is not fully overlapping the chassis all the way around the opening, there is a chance that water can flow past the seal on the outside edge, for obvious reasons. Or water may flow past the inside edge since it's not sealing as it was designed to from the pressurization of the seal against the glass as a component of the weight of the assembly.

There really is a lot more to it than just stringing it in and expecting it to be good.

All I can say is that when I have paid careful attention to making sure the outer edge of the seal is covering the body with a good overlap, all the way around the windshield, I have never had a water problem, and I live in the Seattle area. I strongly believe a leaky windshield is not part of 911 design, it's just a function of incomplete fiddling with the installation. Oh, and I have never used any sealant of any kind.

[david914]

Thanks for the info! Sounds like I need to spend some time "fiddling". I feel better about doing the work myself armed with knowledge gleaned from this forum.

[porsche930dude]

yes very helpful. ill tell you what it would be a minor miracle if i could fix my waterfall of a leak just by fiddleing with the seal. ill definatly give it a try

[aigel]

Injecting silicone is a great idea if you sell the car before you ever have to replace the window or the seal. I spent a whole Saturday removing silicone some previous owner had injected from my SC's windshield channel. What a PITA. It seems to me that this is done a lot when the old seals shrink and harden, instead of biting the bullet and installing a new seal.

Cheers, George

[pmajka]

I am missing something.
to readjust:

do i need to pull the trim insert, reshape it, massage the rubber in the corner (hey no jokes) and reinsert the trim?

[Gene Wilkes]

It would really be nice if you guys would include some pics of the tools you made to do this repair!!

[mthomas58]

+1 on the tool pics.....I've got gaps in both top corners and didn't think it was a problem until I had a leak on my left foot in a driving rain storm on Friday

Never ends, does it? you think you've got one problem fixed, move on to the next, then WTF!

[rnln]

I had exact same gap. I hope I saw Randy's method before I filled the gap with silicon. Silicon works fine but if you come closed, you will see it.

[mthomas58]

Originally posted by Randy Blaylock
Guys, the soft aluminum trim insert in the rubber is what gives the seal it's shape, especially in the corners. It's not critical to have the glass itself perfectly centered, within reason of course.

You can easily close this gap, or gaps at any of the corners, so the seal lip covers the gap. There is enough overlap in the channel of the seal where it wraps around the glass to accommodate this process.

I usually use a piece of wooden shim material like you can get at any hardware store, used for framing up doors and windows. It's a tapered piece of usually pretty soft wood, around 1-1/2 inches wide. Take a file and put a small edge on the thin end, maybe 3/16 to 1/4 inch, with a small radius shape to it width wise that resembles the shape of the aluminum trim in the corners. You could also use the rubber end of a mallet handle, or anything that isn't very hard and has a rounded shape.

Place the tool of your choice so that it contacts the aluminum trim piece on it's inside edge, aligning the tool as flat as you can against the glass while still maintaining a "bite" so to speak against the trim, and using a rubber mallet very gently, strike the tool as needed to move and shape the trim as needed.

Obviously you want to do this gently, using short swings mostly just with the wrist, and make sure to keep the impact vector as close to parallel to the glass as possible. You're basically just sliding the mallet over the glass towards the "persuader".

Along the straighter edges, like the top, bottom and sides, just push the seal out a bit with your fingers to cover the edges of the opening. The seal is designed to take up the space between the edge of the glass and the the opening in the body, and doesn't need to be tight around the glass itself.

I have used this method for years and have yet to break the glass, and have never had a leaky seal.

Great tip. I used a rubber coated tape measure that had a radius similar to the metal trim corner. A few taps with rubber mallet in each top corner and the gaps are gone!

Thanks!

[randywebb]

don't have a pic but I traced the curve onto cardboard and then cut a piece of scrap soft wood into that curve w/a jig saw- tapped it w/hammer

[berettafan]

holy **** i just came across this thread and i can't believe i'm not the only one! i had nightmares about a tweaked unibody, chopped and replaced tops, you name it!

i can not wait to go home and try this out!

thank you RB!

[Randy Blaylock]

Most welcome...

[Superman]

I learned some things reading this thread. One procedures I did not see here is the tweaking of the aluminum trim prior to installation. The trim usually gets tweaked in shipping. You should assume it is not shaped properly. Using the glass as a guide/template, work the aluminum trim to the point where it contours the glass accurately. This might reduce or eliminate the need to smack things with a hammer and block of wood later.

[Randy Blaylock]

Good luck with that.

Stringing the glass/rubber seal/aluminum support assembly into the unibody opening changes the shape such that a post-installation final fitting is mandatory if you want a leak free finished product.

Hammers are good tools, and smacking around a Porsche is a good thing sometimes :-)

[Superman]

I like hammers as much as the next guy. My hammer collection is fairly impressive. But I've also seen those aluminum trim pieces, as delivered. The manufactured shape and the delivered shape are different. On one of my windshield installations (not one of the ones I did), the driver's side lower corner was at least a half inch higher (further from the car) than the other side. That bowing in the aluminum trim was enough to hold the gasket away from the body. Pounding it outward, toward the outside mirror, would not cause the bow to settle down toward the body. It would coax it outward, but not downward. smacking it in a downward direction would have been a good way to break the glass. This is why I give this observation. Smacking is great, but my sense is that waiting until the parts are installed before considering whether the AL trim is shaped properly......is unnecessary.

[JK-81SC]

I had to bring this thread back to life to give a HUGE thank you to Randy Blaylock!

I followed his 6 steps to installing a windshield this weekend (see page 1 of this thread). The install took a bit of time, but it looks amazing. No gaps around the gasket, no sealant needed.

I took my time tweaking the alluminum trim so it matched the curve of the windshield as close as possible before installing the gasket.

When I had the windshield installed, It looked like the picture at the start of this thread. After tapping the trim outward with the wooden shim, no more gaps. I can post pictures of the corners if anyone has doubts about this procedure.

I celebrated by repeating step 6 several times.

Thanks!