orangecurry

A well documented failing of the 993 is the fact that they rust around the screens.

Why? Because there is a 0.5cm gap between screen and aperture which fills with rainwater, and can't drain away.

The screen is bonded at the 'base', but this gap is not filled completely. This gap lies underneath the window-trim/plastic-strip which locks into a groove in the screen.

Here, with the covering plastic-strip removed, shows the gap, groove, and the 'base' layer of sealant holding the screen in place.




So - how to fill this gap so there is nowhere for water to sit.

Porsche Service bulletin 9501 states:
...If no damage is found, the gap between the window and body should at least be filled with "Bostic 6050" sealer and the window trim reinstalled...

Well I can't find any 6050, so I've chosen a special sealant from Travis Perkins. What's special about it?

It low modulus, non corrosive, silicone neutral but particularly a durable, flexible seal that can accommodate significant joint movement. Dow Corning 791.




OK - so what else will you need?




- Masking tape
- Toothpicks
- Toilet roll
- Towel
- used lolly-stick (crucial)
- jug of water

- marigolds - if you have sensitive skin.


If you are experienced in applying sealant to bathroom 'joints' this will help....

NB This is ’my’ solution to this problem – I can't promise (or warrant ) that the screen aperture STILL won’t rust, and if your screen shatters is might be HORRIBLY difficult to remove, but on balance I chose to fill the gap because
a) Porsche say to
b) I think it will reduce any possible rusting to an absolute minimum

Deep breath....................................

1) note or photograph exactly to where the plastic-trim edges extend - you might be surprised how much this varies along the screen sides.
Carefully pull it off.

2) if you have a third-brake-light, carefully pull the painted section up/off the light itself (it's held on with clips), and its matching black rubber sealing strip across the top-edge... then finish pulling off the main plastic-strip. DON'T take off the brake-light itself. You can work around this - just.

3) put the masking-tape edge-down INTO the groove in the screen edge, then fold it back onto the glass - this helps minimise the amount of sealant going INTO this groove.

4) put another strip of masking-tape on the metal/paint side, as close as you can to where the plastic-strip (that you took off in step 1) came to.




5) fill the gap with sealant!

6) use the lolly-stick, or your finger/thumb, to press the sealant into shape. I would keep cleaning the stick/digit (on your towel), and wetting it slightly to help it to glide.

DON'T GET TOO FUSSY YET but get it all pressed in and not too much excess.

7) Once you are 'happy', then remove the masking tape. This is bound to 'pull' at the sealant and make a mess. DON'T PANIC.




whoops - mess; wipe clean easily with tissue-paper



This is 'good', but you can see a 'lip' where the masking-tape WAS



This is not bad, but there is some sealant heading into the groove...






so get a toothpick (TP), and running the TP along at an angle from a clean section, 'lift' out the sealant.




OK - we are now at the point of 'how perfect is good enough'?

The sealant is 'in', the masking-tape has gone, and the inner groove is clean of sealant.

The sealant is also starting to 'skin', so using your wettened lolly-stick (LS) get it smooth AND FLAT, but be careful, as you're bound to put some excess sealant into the groove, or on the paint. Just use small bits of tissue paper to clean the glass/paint, and the TP to keep the groove clean.




Repeat until insane.

REMEMBER - the quality of finish will be hidden from view underneath the plastic sealing strip....

you are simply trying to fill a gap so there is nowhere for water to collect.

Now let the sealant cure, at least overnight but for as long as you can.

Results? I was out in the car today, and it got very wet

You can see that no water is sitting on the sides...







... but here is a small amount in the lowest corner. HOWEVER, it is not sitting against the paint/metal anymore.

Re-fit the windscreen trim, and put the rust/water inhibitor of your choice underneath.

I'll let you know how it's going in a few years time

DanQ

Thanks for the DIY. do you have any pictures of the back side of the window trim strip? I'm not sure how you removed it. I don't want to break anything. (the trim strip or the plastic channel )

orangecurry

As I understand it, OE trim comes off OE screen easily enough - my rear did. The front, being a recent replacement, though allegedly Porsche OE screen and plastic trim, was NOT easy.

I found stretching the front trim along its length, allowed enough deformation to pop a section out. I used a wooden ruler to help get under the trim. Then you continue to stretch as above, and you can work it all out.

Regarding damage, I would think that the trim would fail before the screen edge, and the trim is not expensive.

But for me it is worth the slight risk.

tj90

Thanks for posting, but Im going through a windshield replacement right now and the tech says to avoid silicone at all costs in these areas. Why? Silicone is permeable to moisture and tends to "hold" moisture in the seal. Is it true? Dont know, but when I look at Sika and 3M windshield products NONE of them are silicone. Rather polyurethane.

orangecurry

The actual sealant is up to you - as I pointed out the TSB says Bostik.

But as the sealant I chose is specific for weatherproofing, it would be odd if it allowed moisture in/through?

deleonl1

What is the meaning of "neutral" silicone?

Here's a quote from Colin from NineMeister in another thread.

tj90

My understanding is that there 2 types of silicone. The acetic acid type is the one that smells like vinegar when it cures. The other type does not. Neutral probably activates with some other chemistry.

orangecurry

The stuff I used is specifically non-corrosive; for use on aluminium and metal (and most other stuff)

BUT LIKE I SAID; you use whatever.

orangecurry

Just so that you all stop worrying about my 993

The first silicone sealants were one-part compounds that cured in the presence of atmospheric humidity, releasing small quantities of acetic acid. The market was quick to spot the excellent properties of these so-called acetoxy rubbers. However, it was found that the sealants attacked metals that are susceptible to acids, and they reacted with alkaline substrates. For this reason, they were soon followed by neutral-curing and alkaline-curing systems. Today, silicone sealants lead the market for permanently flexible construction sealants. This success is due to a range of products that were optimized for professional use in the building industry; in glazing, window, metal and plastics construction sectors; as well as for plumbing, kitchen and bathroom applications. Without them, many problems simply could not be solved. Years of continuous research have culminated in the development of alkoxy systems, a new generation of neutral-curing silicone sealants that release an alcohol (methyl or ethyl) as they cure. Aimed at the building sector, they are intended for high-tech applications, window construction, and for sealing both indoor and outdoor joints.

burtraccoon

Its amazing how a genuinely useful article only reaches 8 replies, but other ACTUAL rubbish "junk food for the brain" posts reach far more on average. This is the same for views too.

Sometimes I think Rennlist has too many swinging dicks and not enough content.

YENTE

Elonash

Great article well documented.

However being in the same case (rear screen not rusty) I'm a bit reluctant to cover some area with a sealant without being dead sure that this area is clean and far from any rust start...

callipygian 911

Thank you! I'm going to give this a whirl (after I replace my windshield ... which is probably going to happen very soon considering my outer seal has decided to disintegrate today).

vincer77

Yes, great post. Thank you.

So the rubber "seal" around the window is only a cover, not a gasket holding the glass in place like on other cars? Does it just pull up to remove?

bruce7

For another take on this issue, see this thread:

https://rennlist.com/forums/993-foru...ar-window.html

-bruce

P.S. Porsche sells Wurth Bond+Seal but you can get it directly from Wurth
for considerably less money. Also, Porsche seem to only carry the small tube,
you need the big cartridge one.

IXLR8

Its nothing but "trim".

Yes, but do so carefully and slowly. The tab in the rubber seal then gets pressed back into the groove in the plastic channel that surrounds the actual window glass.