Suggestions for how to go about cleaning the underside of the car

**makenzie71** · 11-19-2018, 09:45 AM

The car has had a major power steering leak for a long time, as well as quite a few other fluid leaks. I got some of them contained, but I'm having a hard time finding others because the larger ones have completely coated the underside of the car in thick grease and grime. I got an inch of sludge in places. I'm scraping off what I can with a putty knife, but I'm going to need something a little more broad and effective to get the rest.

What would you guys suggest?

**osc911** · 11-19-2018, 09:47 AM

Bilt hamber degreaser with spray bottle or brush. Apply neat leave, pressure wash. Repeat.

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**bimmer7410** · 11-19-2018, 09:56 AM

Originally Posted by osc911

Bilt hamber degreaser with spray bottle or brush. Apply neat leave, pressure wash. Repeat.

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I shudder to think of the mess thats going to leave on my (already stained) driveway

**osc911** · 11-19-2018, 10:12 AM

Use the pressure washer at the gas station...

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**dannyzabolotny** · 11-19-2018, 11:27 AM

Go to one of those self service washes and pressure wash the underside there. That’s what I’ve always done.

**JimLev** · 11-19-2018, 11:37 AM

Originally Posted by dannyzabolotny

Go to one of those self service washes and pressure wash the underside there. That’s what I’ve always done.

Do it at night when nobody is around, you can stay longer.
Bring a jack and some spray on solvent so you can soak the crud on the underside good before you pressure wash it.
The 25 cent car washes around here have an engine wash button, haven't needed to use it.

**edjack** · 11-19-2018, 12:16 PM

Best to find a shop that offers chassis washes. They will put the car on a lift and do a more thorough job, and with much less mess on your part.

**BimmrMeUpSnotty** · 11-19-2018, 12:45 PM

An inch thick of crud??? WTH have you done to that poor E39??? !! Jeezuz!!

Power washing it won’t do much but get some of it out. You need to get that thing on a lift, jacked up high and safe if you don’t have a lift, get some gloves on and get to scrubbing most of it off. Once most of the crap is off, then you need to wipe it all down, then nail it with some really good degreaser. Hell, kerosene would be great for cleaning it all off. Then another degreaser stage and you’re good. Man, a good steam gun would do the trick too.

**crazy4trains** · 11-19-2018, 01:09 PM

Brake parts cleaner works really well for removing oil based crud. Just try to not excessively coat rubber stuff with it.

**computiNATEor** · 11-19-2018, 01:19 PM

Dish soap for heavy, caked on oils. Degreasers will dry out whatever grease is there, but they won't carry away the crud that's stuck to the grease.

Or you could find some place that does dry ice blasting.

https://petrolicious.com/articles/cl...tually-a-thing

**bossman1** · 11-19-2018, 04:23 PM

What i have done is buy the largest plastic bins from target and put them under the car. Use Purple Power degreaser, let it sit and then power wash everything. Works pretty well. After you can dispose of the dirty water properly.

**Asbradley21** · 11-19-2018, 04:37 PM

Originally Posted by bossman1

What i have done is buy the largest plastic bins from target and put them under the car. Use Purple Power degreaser, let it sit and then power wash everything. Works pretty well. After you can dispose of the dirty water properly.

Interesting. What do you do with the water to dispose of it?

**makenzie71** · 11-19-2018, 04:50 PM

I got a set of jacks that’ll lift the car 30” off the ground, and a patch of grass I’ve been trying to kill anyway...I just didn’t know how advisable it was to take the pressure washer to the underside of the car. I’ll just do that.

**JimLev** · 11-19-2018, 06:46 PM

If you can keep the pressure washer nozzle 10-12" away from what your squirting you should be fine.
I can stick my hand in front of mine closer than that.

**edjack** · 11-19-2018, 08:09 PM

How about this? http://www.cryo-werks.com/

**computiNATEor** · 11-19-2018, 08:20 PM

Originally Posted by makenzie71

I got a set of jacks that’ll lift the car 30” off the ground, and a patch of grass I’ve been trying to kill anyway...I just didn’t know how advisable it was to take the pressure washer to the underside of the car. I’ll just do that.

Nothing under there is going to be hurt by high pressure water. Obviously, try not to spray it at anything vulnerable like the starter motor or the headlight aiming sensors, but you should be just fine.

**makenzie71** · 11-19-2018, 08:26 PM

Originally Posted by JimLev

If you can keep the pressure washer nozzle 10-12" away from what your squirting you should be fine.
I can stick my hand in front of mine closer than that.

Mine will peel my hand like a banana at 18” lol...but I can keep some distance, I’m mostly just trying break the thick grime off.

- - - Updated - - -

Originally Posted by computiNATEor

Nothing under there is going to be hurt by high pressure water. Obviously, try not to spray it at anything vulnerable like the starter motor or the headlight aiming sensors, but you should be just fine.

Will do thanks!

**computiNATEor** · 11-20-2018, 01:38 AM

Originally Posted by makenzie71

Mine will peel my hand like a banana at 18” lol...but I can keep some distance, I’m mostly just trying break the thick grime off.

Get a nozzle with a wider spray pattern. A 40º nozzle will knock a 2000+ PSI pressure washer down to the 800s, IIRC from watching Obsessed Garage videos.

**CSBM5** · 11-20-2018, 06:59 AM

I've used a Tyvek suit when doing an undercarriage on a lift. With one of those and some goggles, you don't have to worry too much about the mess on yourself. I used degreaser, switching between full on engine cleaner, Meguiar's Super Degreaser (4:1), and purple Simple Green as needed along with brushes and rags, and using hot water to rinse it all off (standard hose nozzle, house pressure).

**bossman1** · 11-20-2018, 08:17 AM

Originally Posted by Asbradley21

Interesting. What do you do with the water to dispose of it?

Normally you can strain the water and get rid of it. and the leftover gunk can be taken to anywhere that collects used motor oil

**JimLev** · 11-20-2018, 10:09 AM

Originally Posted by computiNATEor

Get a nozzle with a wider spray pattern. A 40º nozzle will knock a 2000+ PSI pressure washer down to the 800s, IIRC from watching Obsessed Garage videos.

Right, forget to mention that, I've got a cone and knife edge nozzles.

**philly98540** · 11-20-2018, 10:16 AM

I've never cleaned the underside of any of my cars. I did clean the bottom plastic engine cover when I did the chain guides many years back, but that was pretty simple. You guys must have some serious leaking machines out there.

**Santaclaus4** · 11-20-2018, 10:55 AM

Originally Posted by philly98540

You guys must have some serious leaking machines out there.

My car has a diaper. I put a piece of pig mat on the floor of the garage where it parks to help with it's little bed time "accidents".

**bimmer7410** · 11-20-2018, 11:18 AM

Originally Posted by philly98540

I've never cleaned the underside of any of my cars. I did clean the bottom plastic engine cover when I did the chain guides many years back, but that was pretty simple. You guys must have some serious leaking machines out there.

*hangs head in greasy shame*

**JimLev** · 11-20-2018, 11:41 AM

I've only had to clean the bottom of the engine and the lower engine cover. Never used my power washer on the bottom.
Who gets the award for the filthiest car...Makenzie???