What removes oil and black undercoating but not paint? Options

[mskala]

My car used to leak oil from lots of places. After rebuild, now everything's pretty
good. But, particularly from under the oil tank area, oil has got on a large area
under the floor and longs.

I found accidentally that the CRC Electronic Cleaner doesn't seem to remove paint,
but it is so weak that the black undercoat (wurth?) turns into a huge amount of black
goo that hasn't really come off the car.

I want to save any paint and the white-ish undercoat. Any products that will do this?
I assume my paint is the old lacquer type paint.


Thanks
Mark S.

[930cabman]

I would start with Dawn and work up from there.

[mark04usa]

Next, I would try naptha it should not affect paint...try on test area first. Naptha (lighter fluid) is highly flammable and you would need ventilation.

[Cairo94507]

I use BrakeKleen (the one not sold in CA) and it cleans stuff off easily without hurting or dulling the paint. I never would have guessed it but my buddy Greg has been using that on his cars for years w/no issues on any painted surfaces. As always, if you try this, try it on a spot that you can risk it on.

When we installed my rear glass, we used urethane - what a mess that was because we cut the tip of the tube off so the hole was too big. (IMG:style_emoticons/default/wacko.gif) But it all cleaned up nicely using BrakeKleen on microfiber towels. (IMG:style_emoticons/default/smile.gif)

[JeffBowlsby]

If its oil-based, paint thinner (mineral spirits) should work and not affect cured paint.

[930cabman]

Simple Green

[mskala]

Thanks I will try a few of these tomorrow

[brant]

20 years ago
One of the oil removing citrus cleaners worked for me

I’d use starting fluid before brake cleaner. Brake cleaner can effect some paints. Hopefully not the old stuff on a 914

[SKL1]

Used dry ice cleaning to remove 55 year old Ziebart on my early '71 - left nice but slightly dull original silver paint.
Not cheap (and messy even when you're not doing it yourself!) but very efficient.

[targa72e]

You can see some of the things I used in this thread and how the worked.

http://www.914world.com/bbs2/index.php?sho...l=the+white+car

I general citrus for grease and dirt
Brake clean, red can. Green can will strip many paints.
Dawn industrial cleaner (grease) available on amazon.
I did not have a lot of undercoating to remove. I have soaked undercoated parts in Red brake clean with good success.

john

[rgalla9146]

If its oil-based, paint thinner (mineral spirits) should work and not affect cured paint.

(IMG:style_emoticons/default/agree.gif) I'm with Jeff ... mineral spirits
On high mileage 914 6s oil eventually gets all over the inside front of the left
quarter, the engine compartment and even the bulkhead behind the drivers seat.
wipe off with mineral spitits then dish detergent in warm water.
Be ready for a mess

[BillC]

Rather than cleaners and solvents, try some penetrating oil. Kroil, PB Blaster, etc.

There was a ton of undercoating sprayed all over the trunk of my previous 914. I tried different cleaners and solvents, but nothing would remove the undercoating without attacking the underlying paint. I grabbed a can of PB Blaster and squirted it on a test spot; it took a few moments to soak in, but it liquefied the undercoating without affecting the paint. I went through a can and a roll of paper towels, but my trunk was completely undercoat-free.

The other nice thing about the penetrating oil is that any residue will totally evaporate on its own overnight, so no need to clean the paint afterward.

This also works on tape/adhesive residue.

[mskala]

I bought some naphtha (other searches seem to confirm it will not harm lacquer.)
It is a bit slow-going but I put it in a spray bottle and it doesn't evaporate fast, seems
to be working because I'm getting the underside to show some paint and a lot of the
'tan' factory coating. Bad thing is that it's all a stippled finish so you can't just wipe
everything clean.

I will probably follow up with some of the other suggestions later, to get it to the point
where I can put more undercoating back (without leaked oil in it).

[burton73]

Sierra beige Steve cleaned the entire underside of his car with what I think was some naphtha product. This is back from 2009

Steve's Underbody Cleaning Method
To get the bottom of his car clean enough to eat off of and expose the magnificent original factory paint hidden beneath decades of road grime, Steve avoided shortcuts and did the job completely by hand: [1]
• The Solvent: He used standard mineral spirits to soften the decades-old, thick black tar undercoating. [1]
• The Scraping: He used wooden paint stirrers to scrape away the undercoating one layer at a time. Wood was chosen specifically because it was soft enough not to gouge or scratch the factory beige paint underneath. [1]
• The Wipe Down: He went through hundreds of white terry cloth rags to wipe away the dissolved tar residue. [1]
• The Effort: He explicitly noted that it took nearly a year of "unbelievable amount of elbow grease" to finish the wheel wells, inner rocker panels, and the bottom of the rear trunk. [1]

Best Bob B

[Arkady]

For undercoating type materials, try WD-40...

[worn]

If its oil-based, paint thinner (mineral spirits) should work and not affect cured paint.

Or WD40. Smells a bit better.

[worn]

If its oil-based, paint thinner (mineral spirits) should work and not affect cured paint.

(IMG:style_emoticons/default/agree.gif) I'm with Jeff ... mineral spirits
On high mileage 914 6s oil eventually gets all over the inside front of the left
quarter, the engine compartment and even the bulkhead behind the drivers seat.
wipe off with mineral spitits then dish detergent in warm water.
Be ready for a mess

And well preserved metal underneath. And a mess.

[Ninja]

In order of aggressiveness:

Dawn soap, the original stuff, hard to find, I buy Dawn "Professional" at Sam's Club in a 1 gallon jug. This is the only way I've hit the original formula in modern times.
This is safe on painted surfaces, but it is too strong for my chemically sensitive wife to use in the kitchen. Strips all the oil from her hands.

Full-Bore Hand Scrub
https://www.amazon.com/Full-Bore-Ultra-Scru...B08BW61TVT?th=1

This stuff works GREAT on petroleum based grunge but doesn't remove paint overspray very well. This DOES NOT strip the oils from your hands. This is the only hand cleaner I use on a daily basis.

Citrus based cleaners: Some of these might eat paint. The Go-Jo hand cleaner works well but it's strong enough to strip all the oils from my hands (they will BLEED) and I don't use this for hand cleaner anymore.
If I have overspray on my hands, I remove it with the orange Go-Jo then remove the Go-Jo with the Full-Bore stuff.
Some modern paint strippers are citrus based.
Test this first. It may eat paint.

Penetrating oils. WD/40 and the like. Most won't touch paint. Test first. All leave something on the surface which requires removal if you want to paint/re-undercoat later. These work better if allowed to soak into the grunge.

Mineral spirits, Naphtha, parts cleaner. Work great on grunge, soak if possible, can eat/soften paint but less likely than the citrus stuff. Leaves residue behind. Must be cleaned off with something else.
Mineral spirits was the original solvent that you mixed with the undercoat to spray it on.
I once undercoated 33 new Mazda trucks in a single day.
I don't miss those days at all!

Alcohol: like you buy at a paint/hardware store. This is not great on grunge but worth trying. Might change hue of paint. Very safe (except for flame!).
This is what I use as a final cleaner to remove everything else.
I use more alcohol than any other solvent in my AC work.
Leaves NOTHING behind to jack up your paint/undercoat (new AC parts!).
I've named the resultant surface "medically clean". Not even germs are left behind...

Most of the other solvents are bad paint eaters. You should test each before large use

The chlorinated brake cleaner is an exception but...
This stuff is really bad for everything. I am NOT a "greenie" but I don't use this at all anymore. Many States have outlawed it (for good reason!).

Don't breathe this shit, don't get it on you, and whatever you do, DO NOT use it anywhere near an open flame. When burned it forms a gas closely related to phosgene and will kill you (and anyone close by) quickly.

My steps for cleaning a nasty oily mess from the bottom of a 914:
Pressure wash first, heated is lightyears better. Most pressure washers can stand an inlet temp of 135-140 degrees. Your hottest water in your house is normally 125 or lower.
Hot water kicks ass!

Dawn the crap out of it, let the dawn sit for 30+ minutes. Don't let it dry. You will be hand spraying 10% dawn/90% water (Hot again) to keep the surface soaked. Scrubbing with nylon floor scrub brushes helps. Nasty work!

Powerwash again.

Mechanical removal of thick areas. Scraper, pick tool, razor blades, they make plastic ones which are easier on paint but suck at being "razor" blades

At this point most of the bottom should no longer transfer grunge to a rag. Good idea to use "virgin" white shop rags to determine cleanliness.

Now you start in with the chemicals on just the areas that are still nasty.
You finish the spot areas with alcohol.
Final Dawning and pressure wash.

Once the bottom has been restored/painted/finished I coat it all with Poor Boys wheel sealant. It's like Teflon in paste form.
One of the more unique smells, like bubblegum!
NOTHING (including paint or more undercoating) will stick to the surface for years...


Both heat and cold can be used to remove stuff. Dry Ice can freeze undercoating to the point it will crack and delaminate from the car. Heat works too but leaves a bigger mess. Both methods will take all of the undercoating off, including the original stuff.