now my old 84' corolla.... who cares 
Engine compartment pressure wash
Team Owner
Joined: Aug 2003
Posts: 24,488
Likes: 311
From: Scottsdale AZ
There have been several "engine cleaning" strings that you can find using the search feature that you will find helpful - - -but for me, the short answer of using a pressure washer is: don't.
Depending on the pressure force I think you can do more damage than good. Using it in the fender wells and undercarriage is probably fine- but for general engine cleaning, I'd suggest using a 50/50 mix of simple green on a warm engine. Put a plastic bag around the alternator and the fuse box.
I think you can use a hose with a spray attachment- and a stiff brush on areas where there's build up - - -you may need to hit it a couple of times. Some people use an air compressor to blow off excess water - - for the same reasons of avoiding a high pressure sprayer- I use towels and then let things dry naturally.
As a finishing touch- I use Tire Foam on all the plastics- again- avoid electronics- and wipe down with a damp cloth.
I'm sure others will chime in - - and maybe I'm overly conservative on my approach- but hope this helps.
Depending on the pressure force I think you can do more damage than good. Using it in the fender wells and undercarriage is probably fine- but for general engine cleaning, I'd suggest using a 50/50 mix of simple green on a warm engine. Put a plastic bag around the alternator and the fuse box.
I think you can use a hose with a spray attachment- and a stiff brush on areas where there's build up - - -you may need to hit it a couple of times. Some people use an air compressor to blow off excess water - - for the same reasons of avoiding a high pressure sprayer- I use towels and then let things dry naturally.
As a finishing touch- I use Tire Foam on all the plastics- again- avoid electronics- and wipe down with a damp cloth.
I'm sure others will chime in - - and maybe I'm overly conservative on my approach- but hope this helps.
Thread Starter
Safety Car
Joined: Jan 2014
Posts: 4,496
Likes: 856
From: Walhalla South Carolina
Thanks, from what you guys say and other threads suggest; I will not be using any high pressure cleaning. This is why I love these forums, somebody somewhere has already been there and done that.
Melting Slicks
Joined: Sep 2013
Posts: 2,264
Likes: 455
From: Stella, North Carolina
I learned the hard way...not with my C5, but with my trailblazer. I bought it used and took it to a detailer who as his standard, power washes under the hood. It was running perfectly when I dropped it off but when I picked it up it had what appeared to be a miss or vibration. After 2 hours of dealer diagnosis, I already had one shop give up, it was found to be the fan clutch...which on the trailblazer is electrical and mechanical. It appears some how the power wash damaged it. $550 later and I had a new fanclutch and a smoothe engine. No more power washes for me....
Le Mans Master
Joined: Sep 2013
Posts: 8,900
Likes: 1,074
From: Wisconsin
Do not pressure wash any newer car. You are asking for trouble. It is amazing what you can do with a bottle of de-greaser rags and brushes and then use a good protectant on rubber and plastic. My egine compartment was pretty dirty when I bought it. An hour cleaning and I got to this point. Plan on doing more when spring comes.
Last edited by JR-01; Feb 28, 2014 at 12:26 PM.
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I'm assuming the engine is still in the car.... Yes, DON'T DO IT!!!! Unless you want lots of problems with the electrical.
Electricak connectors were designed to repel water that gets under the hood from normal driving. They were not designed to take the forces developed by a pressure washer.
Electricak connectors were designed to repel water that gets under the hood from normal driving. They were not designed to take the forces developed by a pressure washer.
If you want to wash the engine bay, use a low pressure hose and gently apply the water to the engine.
Burning Brakes
Joined: Oct 2005
Posts: 866
Likes: 4
From: Iowa
I wrapped electrical connectors / altenator / etc with plastic wrap, then I spray the engine compartment w/ a mix of Simple Green or Dawn, I lightly brush some of the dirtier areas w/ a soft paintbrush, I spray/rinse with water using a clean weed sprayer, blow it dry w/ air compressor ... finish w/ some nice detailing.
Race Director
Joined: Jan 2007
Posts: 18,643
Likes: 14
From: Norman Oklahoma - The Only State in the Union with no Blue Counties!
I wrapped electrical connectors / altenator / etc with plastic wrap, then I spray the engine compartment w/ a mix of Simple Green or Dawn, I lightly brush some of the dirtier areas w/ a soft paintbrush, I spray/rinse with water using a clean weed sprayer, blow it dry w/ air compressor ... finish w/ some nice detailing.
Good advise here.
I would add that I sometimes use low pressure no spot rinse at a car wash on a really dusty engine from about three feet above the engine components before the above procedure. Getting the dust out of the way first heps protect shiny stuff from scratches and the low pressure from three up hasn't hurt anything in all these years. Never forget it is a Chevy,,,,they are tougher than most think they are!
When the compartment/engine is clean and dry, Adam's "In & Out" detail spray is awesome ****. You just spray all the plastic, hoses, wiring covers, shrouds, metal, etc. on the engine. Shines them up and overspray on paint just goes away on it's own.
Last edited by Silverbullet00; Mar 1, 2014 at 05:43 PM.
Burning Brakes
Joined: Oct 2008
Posts: 800
Likes: 12
From: Wichita Kansas
I have low pressure washed the engine of everything I have ever owned at one time or another and never had a single problem. But never hit it with high pressure. So do at your own risk 
Le Mans Master
Joined: May 2006
Posts: 5,814
Likes: 414
From: Pittsburgh suburbs Pa.
I do it all of the time on different vehicles , but you have to use common sense and plastic wrap any critical electrical parts and be careful where you direct the water.
Drifting
Joined: Mar 2011
Posts: 1,412
Likes: 15
From: Richardson TX
When I was in college and worked as a detailer at a high end car dealership we used to pressure wash engines ALL THE TIME. The mechanics would too when they finished working on an engine.
No plastic bags or anything, just spray some degreaser on the trouble spots and blast away till everything is clean.
Not that I recommend doing that, but its not like 1 pressure wash is going to ruin your car.
In any case, a rag and some simple degreaser cleans almost anything. Wipe on some armor all or similar product on the plastic surfaces and everything should stay pretty clean and good looking.
No plastic bags or anything, just spray some degreaser on the trouble spots and blast away till everything is clean.
Not that I recommend doing that, but its not like 1 pressure wash is going to ruin your car.
In any case, a rag and some simple degreaser cleans almost anything. Wipe on some armor all or similar product on the plastic surfaces and everything should stay pretty clean and good looking.
Le Mans Master
Joined: Sep 2013
Posts: 8,900
Likes: 1,074
From: Wisconsin
When I was in college and worked as a detailer at a high end car dealership we used to pressure wash engines ALL THE TIME. The mechanics would too when they finished working on an engine.
No plastic bags or anything, just spray some degreaser on the trouble spots and blast away till everything is clean.
Not that I recommend doing that, but its not like 1 pressure wash is going to ruin your car.
In any case, a rag and some simple degreaser cleans almost anything. Wipe on some armor all or similar product on the plastic surfaces and everything should stay pretty clean and good looking.
No plastic bags or anything, just spray some degreaser on the trouble spots and blast away till everything is clean.
Not that I recommend doing that, but its not like 1 pressure wash is going to ruin your car.
In any case, a rag and some simple degreaser cleans almost anything. Wipe on some armor all or similar product on the plastic surfaces and everything should stay pretty clean and good looking.