Removing undercoating

[St.stephen]

Not that this may work in every application or vehicle, however I have found a less frustrating way of removing the undercoating..

I use a 4 1/2" scraper for the large flat areas and a hammer. I basically use it like a sculptor would use a chisel to carve stone. ONce you get underneath the undercoating it peels up in nice sections and moves along nicely.

For the smaller sections, compound curves and the like, I use a 1 1/2 " scraper.

Once you get a little finesse down you can remove the undercoating without even scratching the primer underneath! I was able to do the passenger side innner fender well on the 260 last night in about 2 and a half hours. You can then remove whatever bits and pieces with whatever solvent you like. Naptha works pretty well but stinks to high heaven so please be sure to have fresh air!

[kmack]

I used a 500 Watt halogen work light and a putty knife when I pulled the undercoating off mine. But it also pulls the paint too!

That's why I used the same setup to strip the paint off my car. No chemical mess, and you just sweep up the stuff on the floor when your done. (Or use the shop-vac)

[EScanlon]

A pressure washer used with the right tip and at the right angle will literally slice it off the car.

Granted, it can and will expose weak sections in the sheet metal, (I found one that way) but the time saved in scraping! When I did it, I didn't use the soap, nor hot water, just plain old faucet water and started with the thin angle tip, then worked my way up. The needle tip does an excellent job of literally cutting through the undercoating, dirt and whatever all the way to the metal. That then leaves an exposed edge that you can use the other tips to let the water chisel it off.

2¢

[St.stephen]

Escanlon....Interesting technique....I'll have to give that one a shot. I didn't think anything would get this stuff off the car other than profanity, a scraper or even POR strip.

[Bambikiller240]

When I went aftrer the beginnings of "cancer" on my Z's floorpans this past summer, I bought a 1600 Watt Hair dryer and used that to soften the Matt and Undercoating that I wanted to remove. It worked great and I was able to peel large strips off the car with very minimal effort and NO gouging or other damage to the metal. The dryer works great for shrinking HeatShrink tubing when doing electrical repairs/mods too. Only cost $12 at Wal-Fart!

[peterpit]

I used the hammer and chisel method and it worked great when we got one of those lovely 105 degree afternoons here in Oklahoma (no heat gun or lamp needed). I think I lost about 10lbs in sweat the day i took the undercoating off my Z. Total time for both sides took about 4 hours.

[EScanlon]

When I went to remove my undercoating on the front fender area, I tried the scraper, using both the ice scraper method, i.e. scrape scrape scrape, and the hammer and chisel method. I also tried paint stripper, wire wheels in various sizes and shapes, then the 3M Scotch Pad remover pads and the 3M Abrasive Finger wheels.

The scraper was tedious and caused tons of gouges, scratches and was very tiring and hard on the hands / fingers.

The Wire Wheels did a great job of flinging bits of undercoating all over the place as well as little pieces of wire into face, hair, shirt etc. About all they succeeded in doing was leaving little wire grooves in the undercoating.

The 3M Scotch Pads on disks unfortunately would get clogged faster than I could replace them.

The paint stripper worked quite well, but it was extremely messy. It did however do the biggest area the quickest.

The 3M Abrasive Finger wheels worked VERY well, and gave me a good clean surface removing even some of the surface rust there.

These methods were all attempted, tried or used on one fender area. Then a friend offered the use of his pressure washer.

Did the other side with the pressure washer, and in only an hours worth of use cleared over 90% of the undercoating. I was able to remove undercoating even from inside the strut tower housing. To finish the job, I then used the 3M Abrasive Finger Wheels to clean off the rest. I then went back to the first fender and finished what had been a haphazard job.

After all this, in order to remove the last of the rust, I then proceeded to sand blast the fenders. This allowed me to get rid of the last of the surface rust and "etch" the metal in order to paint it with the POR. After sandblasting, I then used the two steps recommended by the POR folks and used Marine Clean to remove whatever traces of oil, grease may have been left by the undercoating, followed by the Metal Prep solution. This did the final step of etching the metal as well as leaving a rust-proofing coating. I then painted with POR over every exposed metal surface.

Although this may seem obsessive, I'm hoping that I don't have to worry about this part of my car for a long period of time.

Anyhow, sharing so that others may benefit from my experience.

Happy Thanksgiving!

[Bambikiller240]

EScanlon/All:

Heck no it doesn't sound like obsession. Sounds like a smart move to me, of course; I did the same with my floorpan. I used the heat gun and non-metallic scraper to remove 99.9% of the undercoat and Tar Mat, and then wiped the remaining traces of petroleum bits off with Acetone. Then I went to the Marine Clean and Metal Ready, followed by POR15 (inside and outside).

It's the sort of job (like outer spindle pin R&R, or Fuel tank vent lines) that you do CORRECTLY the first time, and don't have to do again for 20 years, if ever.

Hapy Turkie Dai All !!

[skip260z]

I used the cheap 97-cent cans of carb cleaner spray from WalMart, couple of shots and the stuff was running right off. But makes a huge mess.

[Ed]

After you remove the undercoating. And after the marine clean, metal ready, and POR-15. Then what? Do you put new undercoating? What kind?

[Bambikiller240]

After the POR-15, I applied a coat of their ChassisCoat Black Product (supposed to be a super tough paint) inside and out. That is as far as I've gone, to date.

Many people say that you should not use undercoat, as it can trap moisture and hold to the body panels.

I'm leaving my car as is for the winter so I can observe the panels. Assuming no signs of recurring rust, in the springtime I'll probably apply a light coat of some kind of undercoat. Not sure what to use either. Also still looking into options for replacing the Tar Mat insulation on the interior surface. If anyone has had great results, or advice please post. Thanks!:classic:

[skip260z]

Originally posted by Ed

After you remove the undercoating. And after the marine clean, metal ready, and POR-15. Then what? Do you put new undercoating? What kind?

You have to, else the road debris will sandblast the thin paint that Datsun used. Especially at the footwell areas were your feet would be.

If I were to go to the extreme of removing any more undercoat than I had to already, then I'd POR-15 it. That stuff is supposedly tougher than powder coating once cured. Beats the tar/asphalt stuff for protection.

That's what I'd do.