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 Posted: 07-26-2006 04:31 pm
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Paul Prinsen
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Joined: 11-20-2005
Location: Medford, Oregon USA
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Does anyone have a nifty way to remove the undercoat? Tried a grinder with a wire wheel, but that makes a real mess, and just moves the jello around the plate. Next tried paint stripper and a chissel. That works ok, but not much faster than a sharp chissel. Currently using the sharp chissel, and follow up with a scotch brite pad with kerosene, then follow up with super clean. It works and does not damage the integrity of the paint like stripper does. It is very slow going like mowing the lawn with nailclippers. Thought of pre-soaking the undercoat overnight with kerosene on paper towels, covered by cling wrap (so it does not evaporate).

If there is a better and faster way, please let me know.

On a different but related note. What filler was used in the undercoat. I noticed a gray/white fluffy material was left where the gas tank had leaked, and flushed the tar out. Looks like a mineral fiber that starts with an "a" and does not burn. The tar should hold it together so it does not get airborne, but be cautious when you work with that stuff.

 

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 Posted: 07-27-2006 03:10 pm
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colinw59
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Joined: 02-14-2006
Location: Bloomfield/Hebron, Connecticut USA
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The quickest mechanical way I found to remove undercoat is with Surface Strip Discs. They look a little like a hamburger with a small center hole, about 3 1/2' dia x 1/2' thk. 3M makes them #7460 as does Carborundm #39321 and your local Auto Body supply Co. should have them. They're expensive though, expect to pay between $7-10/disc retail. I'm sure I've seen them at Home Depot also. On 15851 I used them with a die grinder as a regular drill is way too slow. You must wear safety glasses and I would suggest a particulate respirator also. It's a very messy process, and it's far easier to put undercoat on than it is to take it off! When I'd taken off the undercoat in the areas needed, I treated any rust by spot media blasting or rust converter, re-seam sealed any joints as required, etch primed, 2 part urethane primed and then re-undercoated. However I have a body shop and I under stand that I have the space, materials and resourses that most don't.

In some of the pics in the link below, you can see were I removed the undercoating.

http://jhppg.com/gallery/74-Jensen-Healey-15851

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 Posted: 07-27-2006 03:29 pm
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Mitch Ware
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Joined: 03-12-2005
Location: Albany, New York USA
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I had my best luck by sandblasting it off.

 

Mitch Ware

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 Posted: 07-28-2006 07:12 pm
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Paul Prinsen
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I like sandblasting, but do not have the facilities for it. My compressor gets breathless with that kind of air consumption. I do have a spot blaster that I will use for the seams and spots. I tried the 3M stripper disc with a drill, but that is slow too. I did not trust my grinder as it is too fast for the 3M wheel. 

My experiment with kerosene worked well. The car was upside down on a rotisserie. Used kerosene soaked double paper towels under a plastic bag with some sand in it (to keep contact with undercoat). Let this sit overnight. Next day, the undercoat had the consistancy of yogurt, and I was able to scoop it up with a putty knife. Rubbed the exposed surface with dry paper towels, which cleaned most of the remainder off. Finish up with kerosene for spots and Castrol Super-Cean for the final cleanup. The result is a very clean original painted surface, or rusted steel. Either way you have a much friendlier to work on surface than with the tar goo. No dust or chips flying around either.

Initial error I made was to not let it soak long enough. What this does is liquify the top, but the bottom remains hard as a rock.  Also, try to scoop away from seams, as you do not want to load them up with this goop. Remove as much remaining stuff with a dry towel. Do not use a kerosene soaked towel, as that will only spread junk around. For vertical surfaces gravity is not your friend, so sand will not work. To keep the contact pressure (for soaking) sandwich some foam rubber in a bag between the surface and some board. Temperature may be an issue. Higher is better in this case. We had 105 F (40 C) weather here in sunny Medford.

Bunched together rags, soaked with kerosene/oil/tar could self ignite. Wet them down with water; dispose with care.

 

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