Cleaning oil/grease off underside

[FLG]

Hey Guys,

I want to sandblast and/or sand the underside of my car the problem is its covered in oil/grease/grime.

Whats the best way to clean all this junk off??

[red79]

+1, I wouldn't mind knowing either...previous owner sprayed indiscriminately sprayed everything with some black glossy stuff that's flaking everywhere

[bull]

If you're going to blast it you don't have to do anything, otherwise I'd recommend getting some paint prep degreaser after you knock the big stuff off.

[tan top]

depending how bad it is !!!  think i would  , spray the under side with engine degreaser/truck wash  , then pressure wash it 

[Troy]

Most media will bounce off grease and undercoating so even if you plan on blasting it you need to clean it first. A high pressure (think commercial) pressure washer works great. The heated ones will even remove the undercoating - possibly the non-heated ones as well if the pressure goes high enough.

Troy

[ITSA426]

I have used brake cleaner to soften the undercoating and accumulated grease, etc.  Then scrape away the crud, including undercoating.  It is messy and really toxic without adequate ventilation and I don't recommend it indoors, or even outdoors without a breeze. 

Sand or media blasting the undercoating is a waste of time if the undercoating is still there.  Sometimes you can get break the undercoating loose and scrape it with a stiff putty knife.  No matter what you do it's gonna be messy under there. 

Ventilation, masks or respirators, and goggles. 

[Chatt69chgr]

I've used a product called Jasco Sealer & Adhesive Remover.  Got at Ace Hardware who had it at $22/gal or $11/qt.  Has been discontinued by them.  Your store may still have some.  Don't know of anyone else that sells it.  It was distributed by Homax Products, Inc. but I can't find it on their website so think it may have been discontinued.  It is pretty powerful stuff.  You put it on undercoating with a brush and it softens the undercoating so it can be removed easily with a putty knife.  Then you use solvent and a rag to finish the job.  Label says it contains Methytlene Chloride, Methanol, Aliphatic petroleum distillates, and paraffin wax.  I don't think you want to breathe the fumes.  Seems like Methylene Chloride is what is in paint stripper among other things and if breathed in concentration can cause heart attacks.  Definitely something to use outside in a breeze and be upwind of. 

[bull]

Sand or media blasting the undercoating is a waste of time if the undercoating is still there.

Not necessarily. It depends on what condition it's in because if it's old and dry it comes right off. I took my fuel tank straps that were covered with undercoating to the blaster and in less than five minutes they had them both down to bare metal. Same with "grease and grime." If it's been there for a long time it won't hold on very well.

Before you spend a bunch of time scrubbing I'd try blasting a spot or call someone who does this for a living and ask them what they think.

[jaak]

On real greasy caked-on parts, Ive always had great results with Oven cleaner (not the 'non-caustic' kind)

Jason

[HOTROD]

On real greasy caked-on parts, Ive always had great results with Oven cleaner (not the 'non-caustic' kind)

Jason

[greenpigs]

depending how bad it is !!!  think i would  , spray the under side with engine degreaser/truck wash  , then pressure wash it 

Yep & I would use GUNK engine cleaner not the stuff used at pressure wash places. It may not get it all but for about $10 it would be money well spent.

[Nacho-RT74]

Degreaser and hidrojet ( better with hot water ), several times, not just once. Thats the best and easier without media or sand blast