Best way to degrease my undercarriage?
 

I'm preparing to put some fresh undercoating on my entire undercarriage and was wondering what the best method of removing old caked on oil and grease is. I've used the POR15 product called Marine Clean before, but that doesn't seem to work well for overly greasy areas.

Thanks for your time.

Minieral spirits ( paint thinner) works great.

Do you want to remove the undercoat?
 

It would seem to me that paint thinner, even mineral spirits, (turpentine, ect) would really damage your old factory installed undercoat. I wouldn't want to do that. You might carefully try regular grocery store "oven cleaner". I would do it carefully, because even that might harm your undercoat. Another product that might get you some traction is Wesleys, Whitewall tire cleaner. It has an acid base and will loosen up engine oil to the point where you might be able to blow off the grease with high pressure water. But you really have to watch what you use, because the factory undercoat usually has petroleum base, just like the engine oil you want to remove.

I'd get a gallon of bar and chain oil, a shoots gun (for spraying chip gaurd), and with an air compressor spray every nook and cranny under the car with the bar and chain oil (chainsaw). This will mix in with the oil you have and you'll never need to worry about rust. Just touch up the wheel wells every year.

If you really want to remove the rust proofing (oil), then I'd find the cheapest degreaser (store brand) and go to a car wash and use the high pressure washer after you soak the underside with the degreaser. I used some stuff from autozone that was like $2.19 a can and it had a nice spray range, and I used this to get the oil off my exhaust to pass inspection. (turbo return line leak).

Steam-cleaning

Spray with de-greaser, let sit, slide sprinkler under there and let it run for a while. Repeat as necessary..

Oh yeah, ha! That's actually a really good idea. Even better, I could hook the hose up to the hot water connection in my basement and really blast it off. Thanks!

That is the truth
 

Hey nothing better then hot water to get it off, though you really have to degrade the grease with something first. I would recommend on a hot day, oven cleaner for an hour followed with a good blast of hot water. I don't think that will hurt your factory undercoat.

I second the steam cleaning.

In fact, I need to do that...

Mine's filthy like you wouldn't believe, and that's exactly what the mechanic told me to do. Said it'd probably cost around $100. I haven't gotten around to it yet but I plan to soon.

If you're gonna wash it off, where is the greasy run off going to go? I'd opt for a car wash and let them handle the grease runoff with their other dirty water. But, as someone asked above, is it already undercoated? and you're gonna add more? or a first application and you want to clean it off before you undercoat?

3rd for steam, followed by a degreaser such as TSP in your power washer and a couple of days drying time before appling the undercoating.

The other question is what are you going to use for undercoating?

This is the best way to clean your undercarriage, in my opinion. :D

http://www.fquick.com/images/articles/16171.jpg

Well, I plan on the areas of repair where I patched the floorboard with POR15 paint to prevent rust. After the metal is coated, I was thinking of using either spray on rubberized undercoating, or possibly rubberized bed liner. I've also heard of people using roofing tar (somebody mentioned that in this post.)

Thoughts?