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MG TD TF 1500 - Removing Underseal

I have been removing some thick underseal from my chassis. A heat gun and a scrapper followed by cellulose thinners to wipe away the last traces.

All good for the chassis but what do I do for the wings ? As I heat the underseal I am going to affect the topside paint.

Is this ok? ( I am heating - not setting on fire).

Do I have to start using a paint stripper - not very effective on the old 3mm or so thick, bitumen based stuff on my car...


Dave
D Moore

If your using a heat gun be very careful and hold it at a distance to your work. Allow the undercoat to warm slowly. The heat from a gun can blister paint and with the heat coming from the backside you would have little warning before paint failure would have occurred.

Bill Chasser
TD-4834.

Also most early undercoatings where asphalt based so a petroleum solvent should remove it. Most likely it is engine oil and road grime. MGs natural and renewable undercoating
W A Chasser

Is this the old "Tar" type undercoating? If so, diesel fuel or kerosene should work and should not hurt the paint.

I did mine outside and used gasoline, but that is risky and I was repainting the fenders so was not concerned about the paint.
Bruce Cunha

It is an old style 'tar' coating. Very thick which was why I didn't think paint stripper would be effective.

I'll try various solvents first I guess.

Thanks.

Dave
D Moore

Paint stripper won’t touch asphalt undercoating. Diesel fuel will dissolve it but it may be labor intensive and messy. It won’t damage the paint other than any grit that may be worked around as your brushing or wiping. I would suggest using a pump sprayer with the fuel oil. Lightly mist the areas you wish to clean and let set. Reapply several times to allow it to penetrate. Then you can begin removing the layers grime. if you have access to a pressure washer I would use it to spray off the fuel oil and grime. You could also use a product called Gunk which is an aerosol engine degreaser. Let it soak in and after several applications use a pressure washer to blow the areas clean.

Bill Chasser
TD-4834
W A Chasser

My TF came to me with some very thick, old and hard undercoating. I tried diesel fuel, gasoline, lacquer thinner, paint remover and oven cleaner. None of them worked. I finally used a butane torch and heated small areas to the point it began to smoke which made it soft and I could scrap away small portions. Once cooled it was rock hard again. It was the worst job on the TF and it took me three months to get it all off. It was on all of the fenders, running boards and even the inside of the engine compartment side panels. It was also on the bottom of the cockpit flat wood panels and is still in place there today.
L E D LaVerne

Mine was about the same as LaVernes and took along time to get everything cleaned up. I used a heat gun to soften the tar and scraped, then used paint stripper to get the paint off, they had it everywhere! I agree with LaVerne, it was the worst part of restoring this car, what a mess! Here's a rear wing. PJ


PJ Jennings

Be careful use a mask. Some underseals contain asbestos.
AJ
A R Jones

I removed it from my car using old style paint stripper, I.e. Nitromors as was, not as is, any modern paint stripper is very ineffective. The old stuff stung when you got it on your skin. Very hard to find now, and needs care in use.
Dave H
Dave Hill

It was based on dichloromethane (methylene chloride) and phenol. Sold now for professional use only. Use outside, and wear protective clothing if you find it.
Dave H
Dave Hill

Think I'll open a new thread to look into a good undercoat to use. Bud
Bud Krueger

In all honesty unless your regularly drive in inclement weather why would you want or need to undercoat? Are you looking for stone protection ?
W A Chasser

Gravel thrown up will cause "stars" in the paint surface without some sort of cushion from underneath. That would be the main reason.
L E D LaVerne

I haven’t recalled any undercoating on the wings I’ve been prepping thus far I’ll have to look at the other car in original paint. Neither mine or dad’s had any coatings that I remember
W A Chasser

Clear rocker schutz is better for undercoating as you can either cover over paint or have it tinted to your car color. It will give you the rock protection and still have the look of just paint.

Another option on getting the old hard tar off would be an abrasive brush for your drill or mini grinder. These are plastic with an abrasive on them. Should not damage the other side, but if they are effective enough would be the question. https://www.amazon.com/Century-Drill-Tool-77443-Abrasive/dp/B0058I3DUS/ref=sr_1_10?ie=UTF8&qid=1514703658&sr=8-10&keywords=abrasive+brush

Then there is this. Never thought of using a metal rotary paint stripper https://www.youtube.com/watch?v=jDGUsEpp1W4
Bruce Cunha

I had to remove the undercoating from a Jeep.
Do not use a high speed tool.
I tried a wire and also a nylon brush on a side grinder all it did was melt the material and flung it all over the place and was as much work to remove form the new location as the original, plus it loaded the grinder wheel making it not work any longer.

The product was a tar base undercoating. It took several bottle, but good old fashion baby oil loosened it’s hold.

I started by turning the Jeep upside down and getting a small area off and then put the baby oil at the base next to the paint, it took a while but the tar started to pull away form the paint and didn’t hurt the paint. It took several weeks.
G D

Freeze it off with dry ice--------
That's what my hotrodder mate does
William Revit

Guys I have been making slow steady progress. Here is what I have discovered to be the best solution ( though not fast).

Use the heat gun gently as Bill suggested. If you direct it at the area to be cleaned but from a couple of inches away to warm slowly.

Keep the scrapper in position pushing it gently. It also gets hot and there is a definite point at which the underseal gets soft, the scrapper bites and you can push it and the underseal sheers away.

You get left with a lot of small patches and smears.

After removing as much as you can get a paint brush, dip in thinners and scrub it around on the surface. The remaining underseal dissolves.

Immediately wipe it using paper towel. Gets the worst of what is left off. Then dipping a paper towel in clean thinners wipe the surface turning the paper and getting rid of it frequently. You need to wipe with a clean surface otherwise you are just pushing the stuff around.

Slow, laborious but does work. No damage to the topside paint ( so far ).


As someone said earlier there is no point in using a rotary tool - it just moves the underseal around and clogs up.

Once the surface is clean and effectively de-greased by the thinners I am using a cup wire brush on my angle grinder to hit the rust that formed underneath.

I intend to use Bilt Hamber products to finish the job. Rust converter and primer, two pack epoxy paint followed by a very hard wax coating they have developed for underbodies ( much harder than waxol etc.)

The two pack epoxy is a glossy black so OK for the chassis. It will take most paints ( according to the label) so I may spray the underside of the wings to match the top colour before I wax.

Dave
D Moore

Well done - the main thing is to find a solution that works for you. Wire brush then rust treatment is the way that I went too. Then a good barrier layer on top.
Dave H
Dave Hill

When I did mine I used poly/nylon abrasive discs on a grinder to finish off. They leave a good finish to the metal.
AJ
A R Jones

We use a German product called Brantho Korrux over here and I must say it is really good. I used a small foam roller for application and it gives a nice durable finish.
Also available in UK and very popular in the Morris Minor world.
http://brantho-korrux.co.uk/index.html
Regards
Declan
Declan Burns

An interesting product and a new one on me. I think that whatever you abrade a rusty surface with you will leave some tiny pockets of corrosion and it’s a good idea to treat them with something. That is unless the metal is thick enough for all of the surface to be ground away, they treat as new metal.
Dave H
Dave Hill

Darn, not available in USA. Bud
Bud Krueger

The underside of my TF was painted with epoxy primer, stone chip, red body finish and two pack lacquer. As a belt and braces approach I sprayed waxoil under the wings. This was a big mistake. The wax may be fine for the inside of chassis members but under the wings it attracted and held every bit of dirt thrown at it. I spent a couple of days with rags and white spirit to clean everything back to a nice, firm shiny surface. I can now simply hose the underside to get everything nice and clean.

Jan T
J Targosz

This thread was discussed between 30/12/2017 and 03/01/2018

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