How Have You Guys Removed Old Undercoating?

[t6dpilot]

I am thinking of undertaking a project that I am not so sure of. While doing some work on my lightweight, I was taking a very close look underneath the floor pans and the rear wheel wells. A fair amount of the old undercoating is peeling or flaked off in spots - guessing maybe 5 to 10%. I realize that is a prime spot for rust to form and I do have some very minor surface oxidization in those areas that really looks like crap to me. It is nothing serious and is bascially cosmetic at this point. I do worry about it progressing from a cosmetic issue to something worse in the future, so... I am considering removal of the undercoating and putting a new coat of something on those areas.

So my question to the group is this - can this be done on a "together" car? And if so, what is the least painful procedure? Here is the story on the car... It was languishing away in the CA desert and pretty dried out, but with very, very little rust (the only repair was the area just below the rear quarter windows and was just few small holes). Package tray, rear seats, floors, and front pan are all in great shape rust-wise and original. The builder of the car had it bead blasted and repainted a beautiful silver and the trunk front fender wells a satin black. Here is the kicker, he did not bead blast the rear fender wells or the bottom of the floor pans.

I would love to clean this up completely or at the very least, touch up the bare areas. Has anyone attempted this without completely stripping the car? Any suggestions? If stripping and recoating is not the right way to go on a complete car, then does anyone have a suggestion for spot touch up? I have a pretty good idea what needs to be done, but want opinions from the experienced group here.

Also, the floor pan is dented up in front of the right rear seat as if it was "baja'd" at some point. I need some recommendations on how to straighten that out also. It isn't much and is only a cosmetic issue that I would like to remedy. I was going to take a 2 X 4 and try to pound it out, but I don't want to damage the chassis. Any help (or talking me off the cliff) would be greatly appreciated. Thanks.

[kenikh]

Wurth Tool:

http://www.early911sregistry.org/for...ad.php?t=13072

http://www.early911sregistry.org/for...ead.php?t=9843

[t6dpilot]

Great threads for reference - thank you. I wonder how many guys did this on a car that was not completely disassembled down to a bare chassis. I also wonder is anyone has done just spot repair. I think I may do just that for the time being since I really don't want to spend all that time on the car without access to a lift. Maybe I will just scrape the areas that are peeling, clean them up, and paint for temporary protection.

[preS]

t6dpilot I have dealt w/ this undercoating thing on two early 911's (65 + 66). The 65 I did use tools like the Wurth tool. I used a paint gun as well. What I have learned is:

- some spots clean up real easy. You can almost get it off w/ your nail. On the other spots were it sits more tight the metal is nice underneath. The problem is that it's hard to see where it's loose and where it's stuck on
- there are a couple of spots where it's hard to reach. Upper inner fender, rear inner fender towards door lock reveiver, the area around the heater boxes, etc. Hard to reach but a lot of surface rust under the coating

On my 66 I am going to do it different. I will have it ice blasted. It's a process which use compressed CO2. It's used in the food industry for example. It will only remove the undercoating, it will not blast away the rust. I will report on the results later. On the pictures the results of trying it out.

Richard

[Scott Clarke]

Scott-
The floor dents can be removed by placing a floor jack with a piece of plywood on top of it underneath the area to be repaired. This is your "dolly". You can then remove the dents with body hammers from the inside of the car. Harbor Freight usually has a cheap set of hammers and dollys that work just fine. I think that you will likely be able to get the floor back to the proper configuration without much fuss.

[Dezzmo]

Hi t6dpilot,

I would highly recommend removing as much undercoating as you see fit and replacing it. I began to see a slight crack in my undercoating right around my left front suspension mount. After further inspection I found this http://www.early911sregistry.org/for...ad.php?t=19038

So if you find any undercoating that's peeling off don't hesitate to take a closer look

[911quest]

Actually this stuff works pretty good. Make sure to keep the garage door open if you try it or you will start to get a little goofy.

[RS-GT]

Does anybody ever tried to acid dip of the whole body, any experienced ?

[preS]

I have seen several cars which were acid dipped. Actually the first car that I saw that had been done like that was a blue speedster in Ohio. What could be seen on that car was that near seems the paint was working. Moisture had creeped in the seems, got mixed w/ the acid (which was not supposed to be any more ..) and worked it's way out. After that I have seen that pattern on more cars that were acid dipped. Some how the stage of neutralizing the acid doesn't work that well.

If I had a bare naked car w/o Alu parts I would opt for to have it baked off. In this process your car gets into an oven. In like 24 hrs they build up the heat to 250? degrees and they have it cool off in the same amount of time. The sheet metal will stay as it was and once the body is cool again you can simple sweep the old paint and coating off.

Richard

[hoffman912]

i hear ez off works wonders to remove old undercoating. never tried it though