dr bob

Cars that sit outside, even under a carport cover, risk condensation in those hidden places even if it isn't actually raining. Under a car cover for extended periods is worse, since it takes longer to warm up and evaporate any condensed moisture. A garage that keep th ecar just a few degrees above outside temps makes a world of difference in avoiding corrosion issues.

Andy, that corner of the rear glass is a known gathering place for car wash water, condensation, rain, etc. Everything that gets behind the rubber will flow to that corner and pool there, especially if the car is sitting at all nose-high where it's parked.. Any breach in the paint, from wear as others describe, from tools used to install the glass, etc, offer a convenient path for the water to get to the metal. From there, it's just a matter of time before the corrosion swells the metal under the paint. I predict that you'll pull the window and find that the visible damage is a percentage of the total, more than a dab of Bondo and a spray can of paint will cure correctly.

The Fixer

Andy your car has started to rust a while ago you're now seeing it come out of the channel.

Reasons are what Dr Bob says. I know you probably know all this.

To have this fixed right and to save as much $ do it this way:

1. don't touch it until you are prepared to spend the money

2. Ask a person for a referral (shops they recommend) so you are treated right and get a good price. I have had whole cars painted for $1000 right that i prepped.

This should only cost $500-700 maximum.

Anyway, make sure they Take OUT the window and BEAD BLAST away the entire bubble and go slightly beyond to bare metal.

Be sure they use a QUALITY filler (Big Difference) that will not attract/absorb moisture and start bubbling 3 yeas from now. I use a little ALL Metal as a first coat which is water proof (full of aluminum dust) but doesn't feather, then a finish coat of something that feathers.

Read this over the phone, sound like you know you stuff (insist it's bead blasted) and get a good price.

This is an easy place to blend and your color is also easy as it's not a metallic.
It will look good as new.

86gtvert

My '87 also has a bubble on the DS however it is in the bottom left corner(lower left curve) of the RQ window. I have checked it out and think by removing the trim and glass and some fairly simple metal work it could be corrected. My concern is then how to prevent it from happening again.

The Fixer

Be careful when washing not to introduce water into the channel, never drive in the rain.

And park it in a humidity controlled plastic bubble.

You'd think it would have to happen again if it happens from the factory.

I plan on fixing mine again in 2030.

M. Requin

I am glad this thread got revived, because I never got around to posting pics of my rear hatch after I removed the spoiler. Here it is, and it looks pretty gruesome. Actually it cleaned up very well, very minor corrosion and no rust-through:



Hope that motivates the inquisitive!

The Fixer

My hatch also had corrosion, under the rubber spoiler wings and in the channels
but the car looked pretty good before all was removed. Only a few bubbles were visible. My car was parked in a port where its butt got wet here and there.

Tape is on hatch glass edge to not scratch it.

upstate bob

Where there's a bubble there's a hole. Looking at the lip areas that have pocking, I would mask off the bad area, glass bead it to clean and smear JB Weld on it to fill, then sand smooth, prime and paint.

Mongo

Part of me wants to tackle the rust repair myself since I have been in a DIY frenzy lately with this car, then send it off to the bodyshop so they can paint and color sand the spot which was repaired.

dr bob

There's a little more to it than that. Beyond the glass beads to clear all the loose stuff, you'll want to use a rust-inhibiting treatement and an etching primer on the affected metal. JBWeld is not really the solution for a car you like, might be Ok for a car you are dumping. Pro body places know how to do this, and their labor time for this isn't much compared to the DIY x2 it takes to half-fast a repair, cry, then get it fixed right.


My first car was a '65 356 SC Cab, and I brought it from the east coast in 1969. Never driven in east-coast winters, it still managed to grow some rashes in odd places. It took a lot of work to fix, and it was always a battle even in the dry SoCal desert climate. Fast-forward to the 928, with it's dip galvanized body and multiple layers of rustproofing from the factory. Grinding or bead-blasting the metal in that area removes all the protection that let the body last as long as it did. When you do a repair, whether for rust repairs or for other body damage, it's pretty important that you restore at least the same level of protection you had previously, and maybe more for places that are known to be vulnerable like the quarters below the windows. That's not something you do with a smear of JBWeld and a spritz of cheap primer. The technology and materials are improving constantly. Let the pro's who deal with this regularly do what they do best.

77tony

If your paint & body shop do the job from start to finish, they will likely guarantee the work.02 T

Mongo

Very true. You can't beat a warranty and professional work.

I'll take a picture today of the rust on my back window. It hasn't really grown much since 2001, but it still is setting off my obsessive compulsive disorder.

The Fixer

I disagree,

Most shops are busy and would even try fixing an old 928 without removing the window if the owner didn't make a point of telling them to.

I see so much BAD old work come off cars that were fixed by professionals. They slap it, sand it and paint it. My car had bad professional work i removed and i have the old receipts to prove it. In fact my car was fixed here and it made the rear quarter real bad as they never removed the window for repair, only used filler over sanded rusty metal..

No one will fix your rusty area better than you Andy.

If you can read you can do this.

A man I worked for as a kid told me this, and it changed my life way back when.

There are $25 gravity fed spot blasters at Harbor freight that work great. Need a compressor)

You can buy PROFESSIONAL GRADE epoxy primer in an aerosol can today from lots of outlets but go to Eastwood Company. $20.

Then take it to a paint shop for feathering and paint blending, you'll be happy you blasted (sand is fine, 'Play sand' from Home Depot $3) to bare metal
and epoxy primered.

Epoxy primer is ALL you need to do to protect and seal up your opened up steel rear quarter. Painters can shoot or apply anything over quality epoxy primer and today's epoxies are incredible.

Mongo

I can't say I don't have experience in rust repair. My Dad bought a 1970 Camaro that had a small rust hole in the trunk area we ground down and bondoed with a patch, sanded and painted. It turned out really good.

Mongo

Here is the rust spot I am battling.

The Fixer

Andy,

When ready buy a Speed Blaster, bag of play sand and

two part epoxy primer:http://www.google.com/aclk?sa=l&ai=C...4-p-25195.aspx

Remove the quarter window, mask the opening w/ 2 mil plastic, Blast the spot, (must mask off the car
and be very careful, wear respirator etc.. PM me if you do this and we can go over it in detail.
Mix a little primer in a cup and brush it onto the bare metal.
2 part epoxy is best and will never come off.

Now that you know it's right you're ready to have a paint shop finish it up.


Install the quarter window (easy once you've done it LOL)