A bubble in my paint

[porschenut]

There's a bubble in my paint, about 4" long by 3/4" wide, up against the drip rail in the area of the lower left corner of the rear window. It doesn't extend to the window trim, so I don't think there's any path for water to get there.

It was there when I bought the car 4 years ago, and it hasn't grown in size or changed. Furthermore, when I press on it, it doesn't give, it feels solid. There are no cracks around it and it is very smooth. This is original factory paint.

Paint experts: is this likely rust or is it just lifting for some other reason? Assuming no rust repair is needed, what's a ballpark figure to get that area repainted?

[pozee]

Based on my experience with bubbles in paint that are hard, they are almost always rust.

I would definitely tackle it. Depending on how involved the repair is, I would guess about $500 or less.

It may be growing on the inside.

[rfuerst911sc]

I'm guessing this is a rear window because it looks like defroster lines in the glass. My bet is the window is leaking and causing the rust.

[porschenut]

Do you recommend I cut it open to see if there's rust there? It may be several months before I can get it to a painter.

[rfuerst911sc]

Originally Posted by porschenut

Do you recommend I cut it open to see if there's rust there? It may be several months before I can get it to a painter.

I don't think there's any question there is rust in there. I would gently pick the bubbled paint away and expose the problem. If it's rust you could brush on some rust converter and at least stop the progression until it can be cleaned up and painted.

[porschenut]

I popped the bubble and you were right, it's rust. It's a thin layer though and doesn't extend much beyond the area I scraped away. Maybe having this ugly wound exposed will inspire me to get it fixed sooner. Thanks for the help.

[rfuerst911sc]

Now the next question to answer is why did it rust? I'd pull your back pad ( interior ) and closely look for water trail signs. It could be random rust but you won't know until you poke around some.

[ja78911sc]

It appears that this is more than surface rust--you may need to cut this out and replace with new metal.

[ossiblue]

O.K., here's the bad news.
You said the car has original factory paint? That means the rust must be coming from the inside--most likely from a leaky window seal that let water collect in the "pocket" of the pillar. It's quite possible that with a bit more probing you will find paper thin sheet metal near the bottom corner, or close to the drip rail. Hopefully, I'm wrong but if it were my car I would thoroughly inspect both sides of the window (even if the other side looks good)
from inside the pillar and along with the rear deck, as stated by others. I'd plan on cutting out all the rusty metal and patch in good pieces before any paint work. Do it once and do it right. Rust is the kiss of death.

[porschenut]

I had the interior gutted a couple of years ago and didn't notice any sign of water leaks in the rear shelf area, but I agree I'd better take another look. The thing is, though, the rusted area doesn't even come close to the window. I did notice that the "valley" of the drip rail has some long cracks along it, from the B pillar all the way to the end of the drip rail, so I'll bet that's where the moisture came from. It probably travelled along the rail and collected there at the end of the roofline.

However bad it is, I'll get it fixed. I was planning to get the hood, deck lid and fenders repainted, but now I'm wondering if it will turn into a full repaint.

[robmog]

it may be mostly original paint.
that looks like a bondo repair to me

[ossiblue]

If in fact there was a crack along the rain gutter then it is quite possible that is where the water seeped in and the rust may have started from the outside--a bit better scenario. It shouldn't take long to inspect the inside carefully as a precaution. Still, the rust looks bad enough in the pictures to possibly warrant cutting out the bad spot.

[porschenut]

Originally Posted by robmog

it may be mostly original paint.
that looks like a bondo repair to me

I doubt it. I know the one previous owner and have the car's full history.

It's hard to see in the photos, but the base primer layer is cream-colored, and then there's a grey primer layer on top of that.

I'll take a stainless steel brush to it tomorrow to see how deep it is.

How could this happen to a galvanized shell?

[old man neri]

Originally Posted by porschenut

How could this happen to a galvanized shell?

Just because something is galvanized doesn't mean it won't rust, it just takes longer.

[afterburn 549]

Mine had same problems same place, If i remember correct there was a plugged drain hole in the corner..Pull the window and check

[ossiblue]

Originally Posted by afterburn 549

Mine had same problems same place, If i remember correct there was a plugged drain hole in the corner..Pull the window and check

Good point!
Porschenut didn't say if the car had a sunroof but if it does this is certainly a possibility and would account for a rust-free rear deck and window opening when the interior was removed. If this proves to be the case, then cut out and replace would be suggested, IMO.

[Zeke]

AFA the repainting of that area, I'd rather be there than many other places. Follow that rust until you see clean metal. Clean it well, sandblasting if you can using lots of duct tape to protect the good paint.

[porschenut]

You're all making some good points. The car does have a sunroof, but where is the drain hole you're speaking of? Is it at the back of the sunroof cavity where the roof slides in? Visible from the inside of the car?

I need to finish up my suspension work and get that buttoned up, then this baby is headed for the body shop.

[afterburn 549]

When you pull the window...even if P. did not put drain holes in the corners, I would..It seems in my distant memory that the left side had a drain and the right did not ( my car) @ any rate it is good insurance

[Zeke]

Sunroof drains are in the tray of the suroof and connect tubes to exits below the rear window lip at each corner. If the hose broke or became plugged up, it would either wet the head liner or the package tray and could cause the rust shown, but from the inside out. The exit tube goes thru a concealed area not accessible without major interior removal. They then exit to drain in the rear lid tray right at the corners. Cars I've seen had the SR exits there when no SR was installed. You can shine a light up inside them and even run a spiral brush up thru them.

I have to think the rust shown in this thread is not internal, but from cracks along the gutters. If it's internal from those tubes, there will be a lot more than can be seen and will require the package tray and insulation to come out to investigate further.