How to fix this rust in wheel well?

[dre]

Hi,
I've got my fender off and discovered some rust where I didnt expect it. It goes from just above the front shock mount to below the vents for the gas tank expander on the horizontal shelf just below where the fender attaches. Heres a pic.



I took a wirewheel on the grinder and removed it. Quite a bit came off. Alas, it went all the way thru in two spots. Heres some closeups.

Right above the shock mount. you can see the hood release cable tube which seems in good condition.


Then also right near the vents.



I've read about people cutting squares and welding in new pieces. Also about people making fiberglass with por 15.

What should I do? Any opinions greatly appreciated!

[dre]

The liquidy looking coating is ospho rust inhibitor btw on there till I figure out what to do.

[Dpmulvan]

Grind away rust with a flap disk or sandblast until every speck of rust is gone, replace rotted through areas with new metal.

[dre]

Thanks dpm, I was hoping for something that I couldn't get after 10 mins of searching.

Details on how thick is tolerable, how to handle the vents, alternative treatments(since the holes are not very big), etc.

I havent found many examples of this particular repair so if anybody has any experience with the gotchas of this location, I'm all eyes!

[Dpmulvan]

If you can sleep at night knowing there's por 15 in your Porsche than fine use it. There's no secret cure other than the obvious.

[E Sully]

A few years back when I had similar issues, I cleaned up the areas, and cut away the badly rusted sections. I was able to source metal patches from members that were parting out cars, from early LWB to SC's. Various sections are the same over the model years. Some patches I made from sheet metal, bending and shaping using common tools I had.
Availability to buy sections from parted cars is difficult today due to the boom in popularity and cars being restored instead of cut up for parts, but there are quite a few manufacturers making replacement sheet metal now.

http://forums.pelicanparts.com/paint-bodywork-discussion-forum/724391-miles-go-before-i-sleep.html

[jjeffries]

I just did this repair over the winter, along with a significant hole further toward the front, where the bumper shock mounts created a dirt trap that lead to rust. I cut out the bad and made all my new pieces from 18 gauge sheet bought from an autobody supply store...nice and malleable. Go to impactbumpers.com under "body restorations" for a number of well illustrated threads about this...that's a UK-based site and their cars, incl galvanized, rust badly....you are not alone. You'll need to remove your trunk seal and I think not pulling the gas tank would be very silly. I put quite afew hours into this but with patience and my MiG carefully dialed-in, obtained great results. Best of luck, John in CT.

[dre]

Back to this. Yup, I'm not sure if I have the energy to learn how to weld. I can probably cut the piece out and fabricate myself a piece that fits and have someone else weld it.

How does one access the backside to treat so that it doesnt rust again?

And jj, es, did you have to deal with 2 vent tubes having rust on and refabricating those?

Lastly, jjeffries, what does the gas tank have to do with this?

[E Sully]

I needed to remove the tank for the suspension pan, and for safety reasons would have removed it anyway when welding. Pulling the gas tank is fairly easy after it is drained. To drain most of the gas, I connected a piece of hose from the outlet of fuel pump to a gas can and turned it on.
As for the vent tubes, I could have fabricated one and brazed it in place, mig is too hot for the tubing. Tubing is available at auto parts stores. Instead I posted an ad on the parts forum. There I found someone willing to cut the sections from an SC chassis they were parting out. The sections I needed are the same on later years.

As to treating the inner sections, I removed rust when it was cut open for repair and coated areas away from the welding with POR15. On the inside of the repair sections I also cleaned, prepped and painted with POR15. Then I also use weld through primer where needed. After welding I dressed the welds and painted again with POR15 through the filler neck opening. I also use brushable seam sealer after painting where needed.


I don't use POR15 to cover over rust sections, I use it on good clean chassis repairs that have been prepped according to POR 15's directions to protect from future rust.


There are some that don't like POR15 for whatever reasons, and use other rust treatments, and cavity sprayers are available to coat inner panel sections.

[jjeffries]

Dre, sorry for my delayed response. Gas tank: obvious why to remove, no? So no sparks fall down there and blow it up real good! Also, I was working inside the frunk area and being able to stand in the gas tank opening was handy.
That inner fender/tub is structural, so you'll want to make sure it's done right. Fab work also needs to be accurate so that the fender will fit back on afterward.
Best, John

[dre]

Yes! GAS + welding not so good. That's a compelling reason. I was concerned that you were saying that they could be connected via a hidden rust pathway. Much to ponder with these excellent responses- thanks for taking the time.

Anybody in denver who likes to weld?