sfl993t4

Pretty common in countries where it rains. I think its worse on turbo's as the heat melts out the little bit of sealant that Porsche (pretty badly) applied between the two plates). Here's mine before and after a recent repair:
















Steve

Metal Guru

Given how clean the interior of the body looks, I'd say that's classic entrapment corrosion. The body coatings that stiffen up (reminds me of the old Ziebart stuff) have a problem in where they are breached, water collects behind them and the corrosion process is accelerated in that area. It could be that the heat shields that are breaching the coating in that area. You might be better off not re-installing the heat shields or spacing them to stand off the panel a tiny bit.

nrubenstein

I don't think that it has anything to do with the heat shield. The body coating comes breached from the factory by the tail panel brace - which you can't leave out as the rear fender gets all kinds of floppy without it.

sfl993t4

Hi

I think that the issue is that the bumper/fender support plate was attached to the car before painting. This left a groove at the top in which water could collect (and a nice flat plate next to it for gathering water) and so porsche used a run of silicone or similar to seal the gap.
The quality of this sealant application was pretty variable and so some cars are fine and some aren't. It seems to be a particular issue with turbos, maybe due to the heat?
Once the water gets past this sealant and so between the support plate and the chassis, it finds unpainted metal which is why the corrosion is so bad.
The main problem is that it is hidden so most people won't know that they have the issue.

Steve

sfl993t4

As an aside, this was the only rust we found on my car, scuttle, window surrounds, headlamp bowls etc. were all fine.
Steve

nrubenstein

Interesting. There was absolutely no sealant present whatsoever. Dirt, of course. Lots of nice water retaining dirt.

Metal Guru

Looking at the pictures of your car, the severest corrosion occurred between the two mounting studs. This is the place where the heat shielding will flex and contact the body.

nrubenstein

That simply is not true. Look again at the picture below. The corroded area is well defined by where the bracket mounted against the body. It's literally NOT POSSIBLE for the heat shield to have caused this rust. The mounting studs are for the BRACKET, not the heat shield.



I crossposted on the 993 forum and they mentioned this link:
http://www.jackals-forge.com/lotus/9...issupports.htm

There are quite a few pictures in here that drive home how little the corrosion has to do with the heat shield.

This one in particular shows it pretty well, although unlike mine, it doesn't look like Porsche sealed it in to the same degree. (Which is probably why he didn't have nearly as much rust.)

Metal Guru

Ah, the missing picture.
That stamping contains a nice channel to funnel water and dirt between it and the body. I think a small mod to that piece to let water pass out would be the best preventive solution. Doors are made this way with drain holes in the bottom.

Bergamasco

Sounds like we all need to take the rear bumper off our cars and have a little look and see just to be on the safe side and then do some painting and undercoating.

kk2

Nick.. When did your wife get a 993 turbo? Or did she always have it??

nrubenstein

She had it for years before we met.

C4Spolar

The workmanship of the repair is awesome!!!

ronnie993tt

Awsome thread with super pics. I'm not sure we need to worry about it Glenn. Our cars barely see rain and never salt. Also, that area of the body is so hot, I can't see how any water would last long enough to rust unless there's a bunch of dirt in there.

LexVan

I wonder how/if this should play into PPI's for future buyers and owners???