Pressure washer PSI rating to clean engine bay? - PeachParts Mercedes-Benz Forum

HuskyMan · #1 03-27-2017, 03:13 PM

I'm looking at pressure washers to use to clean the engine bay, both top and bottom. I'm thinking of using a presoak of Simple Green or some other brand of degreaser then scrubbing lightly with a brush to loosen the grease and grime. I'd also like to use the pressure washer to clean the driveway, roof, brick and vinyl siding, wood and vinyl decking, etc.

Question: is 3000 PSI too much power to clean an engine? Could water sprayed at 3000 PSI sprayed into an engine bay hurt or harm either the engine or electrical components?

Would I be better off with a 1700 PSI rig? Your opinion is appreciated.....

Diseasel300 · #2 03-27-2017, 03:54 PM

You'd be better off skipping the pressure washer in the engine bay. If you use a good quality degreaser and let it "soak" on a cold engine for a while, you should be able to get it just about spotless with nothing more than a garden hose with a spray head after 2-3 applications/soaks.

I have an electric 1800 PSI Karcher and frequently wish it had both more pressure and more volume for the types of things I do with it. I don't use it on any of my cars though.

Dan Stokes · #3 03-27-2017, 04:17 PM

I've scrubbed both engine bays and engines with an 1800 PSI Karcher and had no issues. I do, however, tape up or otherwise protect ALL possible openings into the engine or anything else that might get wet (like the PS pump, etc.) before I spray. One time I had a pro cleaning the driveway and our house (we get algae growing on the house from time to time) and had him wash Mutt's engine bay (no engine in there at the time) with his high pressure commercial unit and it REALLY cleaned the snot out of everything. I don't know how many PSI he was packing but it was a LOT more than I have.

Before any of the above I soak the heck out of whatever is super grubby and sometimes even use the caustic Easy-Off oven cleaner which seems to do the best job out of anything I've tried. Be aware that it'll discolor raw aluminum to a dull grey color so cover it if you want to make it shiny some day.

My experience.....

Dan

tyl604 · #4 03-27-2017, 04:36 PM

I was reading the FSM the other day and happened across directions for cleaning the engine bay. It recommended that you use very low pressure and wrap everything up before doing it. But it was quite specific about low pressure.

Diseasel300 · #5 03-27-2017, 06:11 PM

I'm not a fan of driving water under force into anything in the engine bay. Too many plugs, gaskets, and joints in there that aren't supposed to be wet.

My SDL's engine was seriously grimy from years of leaking valve cover gasket (was still the factory one when I got the car). That stuff was like tar. I used a product called "Oil Eater" that I got off Amazon for cheap and its worked better than any other degreaser I've ever used.

Spray it on full strength with a pump up sprayer and wait about 5 mins then rinse off. Be prepared for a horror show under the car, I wouldn't do it on the driveway. It took 2 applications on my car and it was spotless. Big bonus point - it won't discolor aluminum like the purple cleaners or Easy-Off will.

HuskyMan · #6 03-27-2017, 07:01 PM

Thank you for the referral to the Oil Eater product. Also, I'm looking at 3000 PSI pressure washers; is it possible to install a regulator to dial the pressure back to say, 1700 PSI???

ROLLGUY · #7 03-27-2017, 07:48 PM

I have used the high pressure wash at my local coin-op car wash MANY, MANY, MANY times on engines and bays with ZERO issues. Of course I don't purposely force the spray tip into any electrical components, but everything else is fair game as far as I am concerned.
Others have said not to use purple cleaners, being concerned about aluminum. Based on my extensive experience, my opinion is that they are the best!
Check out: The best degreaser on the planet!

Diseasel300 · #8 03-27-2017, 11:26 PM

Quote:

Originally Posted by ROLLGUY

Others have said not to use purple cleaners, being concerned about aluminum. Based on my extensive experience, my opinion is that they are the best!
Check out: The best degreaser on the planet!

Having started out with the purple degreasers when I cleaned up my SDL (used about 3 or 4 different brands) since that's all that's available locally, I can assure you that the purple degreasers (regardless of brand) will handily turn your shiny aluminum intake manifold black as the ace of spades if you let it sit for any period of time. Even more fun - it takes a wire brush to get the oxide off - and it'll turn everything it touches black until you get it removed.

The culprit is chlorine and chloride. The purple degreasers usually have it in addition to being either an acidic or basic formula. It's similar to putting an aluminum pan or cookie sheet in the dishwasher. Goes in shiny, comes out dull and leaving grey crap on everything.

Funny story about the car-wash wands:

My dad had a 2000 Jeep TJ that he decided to sell. The morning that a buyer was coming to look at it, he decided to give the car a wash at the local DIY carwash. He decided to use the low-pressure spray and do the engine department while he was in there. It was a good 20 minutes later that I got a panicked phone call to bring the truck to tow him home. Apparently the "Ultimate Offroader" can't get the engine wet! We spent the better part of 4 hours with the air compressor blowing water out of just about every electrical plug in the engine bay to get the thing working again, then had to take it to the dealer to get the computer cleared of codes. My dad always owned Fords and frequently washed out the engine bays with no issues at all, so it was very surprising to all of us to find out that the Jeep was hydrophobic!

Dan Stokes · #9 03-28-2017, 08:01 AM

Quote:

Originally Posted by Diseasel300

I'm not a fan of driving water under force into anything in the engine bay. Too many plugs, gaskets, and joints in there that aren't supposed to be wet.

Not so. In my time working at the GMPG one of things we subjected the cars to was high pressure water under the hood. After all, cars are expected to drive thru pounding rain storms without an issue so heavy rain at 70MPH means that there will be high pressure water hitting the connectors, gaskets, etc. So the manufacturers are aware that there will be high pressure water under the hood (you would be surprised at how much water comes right thru the radiator, past the wheel wells, etc.) and design and test to accommodate that.

Dan

Diseasel300 · #10 03-28-2017, 10:54 AM

Rain is not driven straight into plugs, gaskets, and orifices at 1700+ PSI either. There's a big difference between wind-blown rain and high pressure directional spray.

GTO71 · #11 03-28-2017, 05:09 PM

The best and least abrasive technique I found is too use Armor All cleaning wipes to loosing the oil and residue quickly followed by lint free wipes. A power washer will just damage the finish, I cringe every time I see a power washer used on a vehicle.

This takes longer but I have used it on several vehicles and it works the best.

ROLLGUY · #12 03-28-2017, 11:03 PM

Quote:

Originally Posted by GTO71

The best and least abrasive technique I found is too use Armor All cleaning wipes to loosing the oil and residue quickly followed by lint free wipes. A power washer will just damage the finish, I cringe every time I see a power washer used on a vehicle.

This takes longer but I have used it on several vehicles and it works the best.

Damage the finish????????

redghost · #13 03-28-2017, 11:58 PM

Find a commercial cleaners (carpets/homes/dry cleaner) that offers detailing services. I have a local shop that does engine steam cleaning. For $40 the engine bay came out like new. Not the goop coating on black parts, but sparkling clean metal and plastic.

There is another car wash the next city over that puts the car up on a lift so they can get under to spray the grime off, then wash down in the engine bay. Great for long time oil leakage.

TX76513 · #14 03-29-2017, 09:45 AM

Don't forget about the tip - You never want to degrease an engine with O - 30 degree tip. 40 degree recommended if you are going to use a pressure washer.

Dan Stokes · #15 03-29-2017, 11:13 AM

Quote:

Originally Posted by Diseasel300

Rain is not driven straight into plugs, gaskets, and orifices at 1700+ PSI either. There's a big difference between wind-blown rain and high pressure directional spray.

Actually, that's EXACTLY how GM tested them. Not sure about Mercedes but I'd be surprised if they didn't "stress" the underhood bits, too.

That said, I don't deliberately force water where it doesn't need to be but in 50+ years of doing this I've never had an issue other than some Ford distributor caps from the 60s that had to be dried to restart the car. They're better now - my 'Stang has survived many a underhood wash.

After seeing how we tested stuff at GM I haven't given a second thought to pressure washing. It's something one can worry WAY too much about.

Dan