safulop

After owning this S4 since November I finally found the rust spot. It is growing out of the rear hatch window channel under the spoiler, and so is not generally visible. I would eventually like to get this repaired, I'm assuming it will involve removing the hatch and rear window, grinding out the channel, and then repainting the entire hatch. This is sounding quite expensive! But eventually it will eat through the entire frame and become irreparable, I guess.

I plan to monitor this rust for a little while to see if I find it growing. I will be amazed if I can get this fixed for less than $1000, given what I know of the body shop I've used several times for work on my 944. I'll be seeing them soon to fix my front lower spoiler and I will get an estimate on the rust repair. Does anyone have experience with this particular job? I can see from the design of the rear hatch (skyward facing window frame with no drainage) that water pooling in the frame and subsequent rust must be a common issue with this car.

-Sean

Nicole

I've seen rust progressing out of the channel of the rear quarter window of a 25k mile 1991 S4 that had always been garaged... it happens to the best of 928s.

safulop

I've heard a lot about rust in the lower channels of rear quarter glass; I have dodged that bullet on this car, and all the windows have been resealed in recent years for repainting. I'm a little surprised the rear hatch window went this bad, it is possible that it was not properly prepared for repainting. My quarter glass seals look very tight with no rust so far.

JHowell37

I think the major culprit when it comes to rust is backing the car out of the garage to wash it, and then pulling it right back in after towel drying. Meanwhile there's a small pool of water in the window channel that takes a few days to fully dry.

If you can remove the hatch and pull the trim and window yourself, that should save some time and money.

James Bailey

Dust and dirt also collects in the channel and holds mosture. And as mentioned the more the car is washed the more likely the rust. The old very brown 1980 lives on the street in front of my house and gets one side "washed" everynight by the sprinklers. That corrosion testing has confimed that the rear window channel and rt 1/4 will both rust. Even the alloy door has some white crumbles under the paint.

The left side the "control group" in this study shows no such corrosion. The subject can be seen in Mapquest photos 2268 Rutgers 92626......the rust however is not yet visible from space.

Dean_Fuller

My son's car had rust in both the hatch glass bottom and rear lower quarter windows. ALL of it was surface rust and I could wire wheel off and out. For the quarter windows I removed the glass and rubber. I drilled a hole in the channel where water would naturally pond. The hole was drilled before primer, paint and clear so the hole edges should not rust any time soon. As far the the hatch glass is concerned the water just ponds in the channel under the trim. My "fix" for that was after paint I filled the low channel with water proof caulking so the water is displaced and not allowed to pond.

safulop

^^^^^
Smart trick, I may ask the body shop to do this when they fix her up.

Nicole

Where does the water go from there? How is it drained to the ground? Does it drain directly into the wheel well?

Dean_Fuller

On drivers side the hole drains in the same area that houses the antenna base ( on OB's ) behind the wheel well trim ( I think that keeps a great deal with trash from coming back up through hole )....so it goes to the ground.

On the pass side the hole is behind the gas tank neck....so it too drains to the ground.

Those channels hold a great deal of water that just ponds until evaporated. This "fix" drains both windows if the car is sitting on a flat surface. ( like most garage floors)
I "found" the low spot by pouring water in it and letting it pond then marking and drilling. If your painting its an easy modification. I feel as long as the hole edges are sealed from moisture with primer ( in my case epoxy ) , paint and clear coat rust will not set in. And is MUCH better than just letting the water pond in there.

It was odd to notice that the rubbers around the quarter glass does NOT fill the body channel. Maybe when they were new the rubbers fit well enough on the outside edge not to allow water inside the channel but after a couple decades....that part is not so water tight anymore.