Discussions board for the classic MG MGA.
I have a great deal of undercoater on the bottom side of the trunk and other places. Does anyone know of a good way to remove it. In those areas where oil or grease has been on it the undercoater seems to be soft and can be removed with a scraper. Probably an indicator of how it may be removed. Thanks for any ideas you have. john h
I've never done it myself but if it is tar-based, I'd try a heat gun and a putty knife to start. Followed up with mineral spirits and steel wool.
I had good luck with mine exactly how Chuck suggested. I used a heat gun to heat a small area at a time, then scraped with various scrapers. After an entire panel/large area was finished I went over it with mineral spirits. When I say I had good luck, that is reletive as the job is a big PITA. I am glad I'm done with it....Good luck.....Don
Heat gun, putty knife - but knock the sharp edges off the knife on the grinder so it has nice rounded corners or you'll put neat little pointy creases in your fenders.
JIM
I should also add that the rotisserie I am using made the job much easier....Don
I have had to remove undercoating from several restoration projects. I generally start by trying to take it off with just a putty knife and hammer. If the undercoating is hard and brittle and not adhering well it will flake off in large chunks. This may work in some areas but not others. You have to be care full not to hit it too hard and dent or gouge the metal.
For the areas that this does not work I go to the heat gun as described above. Be careful with the heat, as it can start the tar on fire. It is also a good practice to put down some plastic or paper to catch any hot tar. You will also need to have some ventilation as the melting tar gives off fumes.
Once the majority of the tar is off, I have used Gumout carb cleaner to remove the remainder of the material. You definitely need good ventilation when doing this.
Don
Follow the suggestions above. Also look at Eastwood's web site. They have a undercoat softener available as well. I've never tried it, but like the idea. I did half of my B and then decided to wimp out and have it blasted.
Yesterday someone suggested I try oven cleaner. I bought some spray on, sample sprayed an area last night, this morning the undercoater on that spot came off with very little effort. I sprayed the rest of it a while ago and will leave it all day. Hope the results are as good. john h
If the paint on the other side of the panel isn't a factor I've found that applying heat to the back side of the panel will loosen the grip of undercoating as well as body fillers and allow them to be removed very easily. I've used both a propane torch as well as an electric heat gun with good results, just keep the heat moving about so as not to overheat the metal and watch the surface for signs of bubbles or wrinkles and then it's ready to come off easily with a scraper in fairly large chunks.
When I was young(er) we had to clean an old commercial stove with years of grease and grime caked on.
We took it apart and put the pieces into double garbage bags and tied them off after spraying the bejeezus out of them with oven cleaner.
We left them tied up out in the sun (black bags) for a day and when we took them out, the stuff all wiped off pretty easy.
I wouldn't have thought about oven cleaner for undercoating - though tar is kinda like grease, so it makes sense.
Thanks for the tip, and don't breathe too much of it in.
JIM
I had the pleasure of the undercoat removal process last spring and used a map gas torch with it's own igniter so it only made heat when I need it. heat some... scrape some... and on and on and on followed by the steel wool mineral spirit wash.
I have done this also. In my opinion you need to put the the body on a rotisserie so you can turn it on its side. I used a propane torch to soften the undercoating and then scraped it off with a putty knife. I then sand blasted the entire bottom of the body. You will have a real hard time getting the undercoating out of the corners etc. thus the sandblasting. This needs to be done outside and wear leather gloves. Hope this helps, Paul
I used a needle scaler, carefully, on a TR6 recently that hard dr/hardened undercoating and it worked really well. For softstuff a wire wheel on a grinder also works, but can be messy.
After a couple of days and several different processes I am now convinced that Bill Youngs idea of the use of a good heat gun to the other side of the panel works the best overall. The oven cleaner worked well on some spots and not on others. If you can stay with it and remove it before it dries it works best. If it dries it seems to make the undercoater brittle and even harder to remove. Thanks to all for the help
Actually I've had good luck with a rotary wire brush, in an air-powered die grinder. I know, the brushes are usually rated for only 4500 RPM's or so. I wore heavy clothing and a full face mask. Probably somewhat in danger of flying wire pieces, but I used it successfully removing lots of heavy gunk. Any other sort of rotary unit (scotch rotolok, etc) doesn't work because the tar gums up everything quickly. But with the wire brush that doesn't seem to be an issue. Much cleaner and more complete that heating up that gooey stuff!
I used a wire cup brush on a angle grinder and it worked great to remove undercoat. The undercoat was dry and mostly hard. Also removed thick bondo and paint off of the fenders and doors without damage to the metal. Twisted wire cup brush is most aggressive but straight wire may be used based on conditions. Just don't use too much pressure.