Best tool to clean/remove years of oil/dirt buildup?

I am talking about cleaning out the engine compartment (engine is out) and all under the car. The buildup is so bad, my regular pressure washer doesnt seem to do the job well. Any reccomendations? Hoping to get it spotless to paint the engine compartment and new undercoat under the car.

Get a biodegradable solvent, spray it on, let it set, pressure wash, rinse & repeat until you get the desired results. Been there, done that & ain't no fun.

it really depends on how deep your pockets are... take it to a professional sand blaster maybe?? the undercoating sucks to remove....... SUCKS, but if you want it spotless.....

Soak with the GOOD Easy Off oven cleaner then pressure wash

If you have a place to do it off driveway,or yard, i used kerosene in a garden sprayer on a portable kwicklift, just spray enough without it dripping or running everywhere ,with a garden sprayer, soaked it and let it set over night , 3 times, then used a pressure washer, it took grease ,oil, mud and old undercoating off. About $20 on kerosene and $20 of simple green degreaser.

I did all of the above, but the best tool I found was using a needle scaler. You will need a decent air compressor to run the scaler, mine is a 60 gallon upright. I didn't treat the undercoating at all, just hit it dry with the scaler and it pulled all that crap off. It is hugely messy however and tiring as you're using a mini-jackhammer overhead that is heavy and pushing back at you while you hold it in place. I had to take my time but it really was effective. After that I did the easy-off bath to get the lesser crud or in places where I couldn't get the needle scaler. As stated above, this process is no fun.

I use a needle scaler to remove old undercoat. That must be some really hard baked on grime!!

Scott Bowers said:

I am talking about cleaning out the engine compartment (engine is out) and all under the car. The buildup is so bad, my regular pressure washer doesnt seem to do the job well. Any reccomendations? Hoping to get it spotless to paint the engine compartment and new undercoat under the car.

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When I started restoring my Duster I put it on a rotisserie and sandblasted the entire thing. The factory undercoating is VERY hardy material. After blasting through the grease, dirt, and muck I noticed that the undercoat took a lot of effort to get through.

This made me realize something. That stuff had been in place for 50 years and was still holding strong. It was applied in a wonderful era, prior to the EPA and it's meddling ways. So, considering that the undercoating had been protecting the car for that long, I decided to leave the factory undercoating wherever it was still in place once it was free from road grunge. I applied new undercoating over the entire underside, but in some spots it just went right on top of the factory stuff. Double protection, never a bad thing right?

All this to say, if you can wash or blast away all of the muck and grease maybe you want to leave the factory undercoating in place and simply spray new material over top to protect any unprotected areas that you uncover with pressure washing / sand blasting. Just something to think about.

whatever you use, make sure it is banned for sale in the peoples republic of commiefornia
thats how you know it works

I haven't much a good pressure washer won't touch. You must not have a "good one".