Undercoating

[mikes]

My '73 coupe has been soda blasted and repairs to the fortunately small areas of rust and unfortunately large areas of bodo are now started. Rubbery, tough, ripple surface undercoating was removed during the soda blast process. I assume that undercoating was factory or dealer applied on delivery? I would like to replace that undercoating once the underbody is repaired, primed, and painted. What product best duplicates the look of the '73 material.

Thanks

 

[Peter Coomaraswamy]

I can show you later

Hi Mikes:

I am doing a full undercoat this week-end. I have a product that I think is going to match the original (mfg.) undercoating. I will send some pics and the product name and you can see what you think. Here is a pic of the car now- I'm scraping, not blasting, but I wish I blasted. I think I lost about 10 lbs. scraping this stuff off :-(

 

[polaris68]

Here are a couple shots from my undercarriage. I used the Wurth product.

 

[Peter Coomaraswamy]

Wow

Ok, now I have something concrete to strive for in undercarriage prowess! Nice detail!

Thanks for the shots

 

[Nicad]

Hi Mikes:

I am doing a full undercoat this week-end. I have a product that I think is going to match the original (mfg.) undercoating. I will send some pics and the product name and you can see what you think. Here is a pic of the car now- I'm scraping, not blasting, but I wish I blasted. I think I lost about 10 lbs. scraping this stuff off :-(

Peter, what has you scraping technique been? I tried a heat gun, but it seemed too weak. Will try a torch and scraper perhaps next. I wish I could farm this part of my undercarriage resto out. Polaris 68, that shot of your underside looks amazing. Is that a Coupeking exhaust?

 

[polaris68]

Yes, it is a Coupe King exhaust, but it is an early one. Not as nice as their current offering. Thanks for the compliments.

 

[HB Chris]

I have always wondered if the black undercoating was applied by the factory. I have not seen a window sticker with a dealer installed option for undercoat although it is possible.

Underside is a greyish color, body color overspray wraps around the underside in places, black undercoat applied last. My '69 2002 has the grey underside with an orange/brown cosmoline type undercoat but only around floor portholes, frame rail, rockers, spare tire well, etc. It came off pretty easily with Easyoff oven cleaner and then a wipe down with thinner. Much easier to clean then the coupe's belly which I haven't tackled just yet.

 

[Nicad]

Interesting that the 2002 has easier to defeat undercoat Chris. Here is a shot of the one area on mine that is not covered in Black undercoat.

 

[61porsche]

Chris,

I believe John Hein's coupe, originally a euro (from Italy?), has the tetroseal window sticker on the back window still.

In the early days of undercoating, it wasn't waterproof. It had to be sealed which is what's done on early Porsche's now when restored. Karmann didn't even prime first, just seam sealer. They did do a water pressure test before leaving the factory.

With etching epoxy primers now used first ( don't know what west coast restorers are presently using), then rubberized undercoating, and finally any top color for a seal, what's done now is far superior.

 

[HB Chris]

Thanks Jerry. I think US coupes had the back undercoat from the factory. Maybe it was a Hoffman requirement. I do find it interesting that the 2002 had none of the black stuff though. I will post a photo from the laptop, can't get them from this iPad.

 

[Stevehose]

My car has a lot of undercoating on it, I don't think it was all factory applied because after I acquired mine I spent a lot of time scraping the overspray off the rear valence and chrome bumper risers, and it was also on the lower part of the radiator and (still is) on the power steering pump, as well as other parts. Doesn't seem like factory to me.

 

[HB Chris]

Yours might have gotten an extra dose by a previous owner!

 

[John Buchtenkirch]

I would say that the tan or light gray undercoat is likely the factory rubberized undercoating. Any black undercoating is likely installed by the dealer, some body shop or a previous owner. ~ John Buchtenkirch

 

[Peter Coomaraswamy]

Scraping technique

Hi Bob,

Good question; I tried everything known to man (and a few that are not)! The "factory undercoating" (mine is a 74), was grayish and applied pretty well. The only thing that really gets ALL the undercoating off is blasting or dipping. Short of that you'll have to scrape and use all types brushes, scrapers, wire wheels, etc. It is a work-out! To completely clean the bottom I used oven cleaner and a power washer, that also loosened up allot of the bad undercoating and made it easier to scrape off. I too used a heat gun and it did not really help.
Regarding scraping it all off, when I saw it was on so well, I carefully scraped all the lose stuff and then feathered the edges down and cleaned up the bare metal. When I was done I used a self-etching primer and then sprayed 6 bottles of undercoating at about 60 psi. I'm pretty happy with the undercoating product I used but not the final results as I will have to do a little more feathering and hand apply some areas and then re-shoot for texture. Then I plan on painting semi-gloss black. It's not "factory" but I think it will give me the desired look once I'm done. I included a couple of pictures but my phone camera did not work too well.

 

[Nicad]

Peter, just curious if you tried a propane torch to loosen the undercoat before scraping? I did this on my Corvair and it worked well. Not looking forward to this job really.

 

[Peter Coomaraswamy]

Too scary

No, I did not try direct flame, even though the gas tank is out I would be afraid I'd burn something up! I noticed Eastwood had some undercoating remover- I did not try it but it might be worth a try and if it works then I'm sure allot of people would like to know- sorry I can't be more help this car is allot of trial and error- hopefully more trial than error:???:

 

[pamp]

Labour of love

At the end of the day....your car, your work...never ends. What the coupe is about for me.
We can drive the state of the art....sure. Not the point. Mine is my coffin. Keep up the good work, she will love you back.

 

[Nicad]

Tried a propane Torch this evening. Couldn't seem to budge it unless I really got it hot and on occasion flaming. That is not gonna happen. Too much unknown smoke and risk. Might like to try Eastwoods undercoat solvent but they won't ship to Canada.

 

[Peter Coomaraswamy]

a little update

I took some pics last night- they're a little grainy, but I did knock down the high spots of the old undercoating and applied more of the new stuff. It was very interesting, I used an abrasive (3M) wheel and it took down the old undercoating but the new stuff I put on was immune to the abrasive wheel. Really tough stuff! I included some pics and one of the product I used. Are you in a hurry for the removal stuff because if not I could buy a can and send it up to you in the mail- if it works you can send me the cash. It will probably take 10 days or so to get it in and up to you.

This project would be fun if it was not so freggin hard!

 

[Nicad]

Thanks for the offer Peter. I'll try a couple of other ideas in the mean time. I might be down in the US in the next couple of weeks so will hold off for now.

Bob.