I noticed this last fall, but just now have started to get to looking at this. I appears that water has been pooling in the indentation just below where the master brake cylinder would be on a C4, now causing some corrosion to start.

It looks worse than it really is, I have not cleaned it up at all, and its solid to my probe, so it appears to be surface rust. However, rust it is, and this appears to be a spot that, if it gets wet, the water can sit in the indentation and eventually cause problems.

I am not sure where the water would be coming from. There is a trace of rust on the edges of the plug that is put into place given this car is not a C4...but that could be either water coming through behind the plug, or water coming from above. There could be a number of sources, like a bad seal around the hood (mine is fairly new and appears to be glued in tight), drainage from the A/C unit is plugged, or some other source.

Rob C. said he checked his 1995, it had the same issue. I would be curious if others can check their cars. I suspect cars in dry climates like CA or inland will not have this problem even if its a design issue, it has to be cars in the wetter climes like the Pacific Northwest.

Anyways, I plan to clean it up, acid wash and perhaps POR-15 or seam sealer, not sure which. Regardless, it does not solve where the water is coming from...so I need to watch it (unless someone has seen this). This is over 15 years so I doubt if its soaked all the time.

I checked the other side and around the trunk area, its perfect. I have my car up on the hoist quite often (its there now) and no signs of body corrosion anywhere, so this a surprise.

It would be interesting to check out C4's as well if they have problems. It might be a lot harder to see it given the brake master will be in the way.

I could also just have a seal problem and its localized to my car, but the fact that Rob sees it on his 95 C2 scares me.

Anyone else seen this?

Cheers,

Mike

 

Mike, I will check mine tonight. Hopefully I will be able to see past the master brake cylinder.

I'll let you know if I spot anything.

 

Have you actually seen any water? The close proximity to the master cylinder causes me to suggest that rather than water, perhaps some brake fluid has caused the paint to get eaten off and, once bare metal was exposed, rust to form.

 

That area usually has a coating of 'basecoat' but no clearcoat.

Between you me and the lampost, I would get a small container of *rust converter* emphasis on converter (not remover or destroyer) and, using a very small paintbrush, liberally apply some on the affected area. Let the first one dry and then apply a second coat.
The converter turns existing rust BLACK and HARD and that'll save your bacon.
Then I'd apply some 'touch up paint' so as to merge it with the surrounding area.

Rust converter usually comes in a small white plastic container at your local auto supplies store.

Gerry

 

Hey Mike,

When I looked at my car before buying it I saw a rust puddle like yours, it wasn't quite as much and just wiped off with a wet rag. There was no damage but I couldn't figure out how it got there. Later on when I installed a strut brace I noticed some more there but this time it was wet with windshield washer fluid.

The little elbow that goes into the hood was leaking and it dripped the fluid down there. When I tried to check the elbow it just fell apart in my hands. I guess the plastic over time deteriorates to nothing. I can't remember if the part was NLA or backordered so I just put an elbow from an autoparts store in to replace it, there is a second hole there that I used. Since then no puddle or rust mark.

You might check the washer fluid elbow in the hood and see if that is where it is coming from, because I almost never use them it took a while for me to find it.

EDIT: In the picture below this is the fitting I am talking about, you can actually see what is left of the old white elbow in the black plug. The washers still worked, it was just a leak at the hose to fitting.

 

Mike - yup, saw this before on a previous C2. Figured it was either w/w leak per Erik's suggestion and/or leaky hood seal.

 

To better understand the various systems on my 964, I took my trunk carpeting out shortly after I purchased the car...fortunately I did this, as one day I saw a puddle of water at the base of the floor pan?

Rust is forming at the base of my windshield, which I'm sure has formed tiny holes under the seal? I believe the water that drains into the trunk starts at the windshield gasket, then runs down the trunk through tiny rust holes and forms a puddle as seen in the photos.

A word of warning to those with rust at the windshield base, check behind your trunk carpeting!

(note: Photo from AP Design)

 

POR-15 is great stuff. I used that on my old rusty SUV many years back.

 

I had a little bit of rust in that exact spot and figured it was started by spilled brake fluid and/or steel shavings. I did exactly what Gerry suggested and used rust reformer in the well. Not the prettiest look right now, but my plan is to hit it with some polar silver paint.

 

Just wanted to tell you guys that this is not only a 993 problem, it used to happen to my RSA as well. I used to keep a roll of paper towel in that particular spot and one day when I opened the trunk it was completely soaked. No rust though. I never figured out what caused the water to gather there, tested all the seals in the trunk and they were all fine. Haven't had this happen on the 993, but apparently it is a problem in some cars.

 

It doesn't look like a brake fluid leak as when that happens the paint usually shows signs of blistering around the spot and I don't see that here. I'd second the rust converter idea as I think the POR treatment, while very effective, may be overkill. I'd just wipe out the area with a damp rag, let it dry throughly then paint on the rust converter. If you're not happy with it after a while, then do the full on POR job.

 

Not sure which method I will use, but I have the POR stuff in the shop. Regardless, where does the water come from and can it be stopped?

 

I looked @ my C4, & there is nothing there, no water or rust. The question is where is the water coming from? A drip from the windshield washers, or some other seal that is failing. Maybe your Targa has some slightly different seals some place?

I found some surface rust around the drivers side headlight bracket area. It seamed like the PO had a battery maintainer on the car & might have overcharged the battery, spewing acid out the vent tube.

 

Mike,

Could it come from underneath the black triangle?

What is underneath it? Can you open it and see?

There is also a little more rust away from the triangle towards the front.

I'll check mine.

 

Just took a look at my RHD UK car and it's got the same area but on the opposite side. Mine wasn't wet or rusty but there were specs of metal down there which have rusted. Also noticed the sealant in that area is a little slap dash and doesn't quite seal the join properly.

I think I'll put some extra seam sealer down there at some point and paint over it to be sure of no issues down the line.

Thanks for pointing this out.