does it hurt anything to power wash your engine?

HeXen

Diamond Member
Dec 13, 2009
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use some purple power and power wash the engine?...well actually i mean everything under the hood. If its not safe then what is a good method for keeping under the hood clean?
 

Ryan

Lifer
Oct 31, 2000
27,519
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Generally - it can be a bad idea to spray your engine bay down....especially with a pressure washer. You don't want to force water into any kind of wiring, fuse boxes, etc.

In the past what I always did was liberally coat my engine bay in something non-corrosive like Simple Green, let it sit for a few minutes, then lightly spray it off with a water hose (low pressure). Avoid areas like your alternator or fuse bozes - you might want to even consider covering them with a plastic bag. You have to do this at your own risk though. I would not do this frequently - I used to do it once a year to my previous cars...but then I stopped giving a shit about it.
 
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Pulsar

Diamond Member
Mar 3, 2003
5,225
306
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Rinsing it is fine.

Steaming it is fine.

Using simple green diluted and rinsing with a hose is best.

POWER washing is a bad idea. There are too many connectors, electronic boards, etc that are water resistant to splash but not to sustained high pressure.
 

phucheneh

Diamond Member
Jun 30, 2012
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Define 'power wash.' I would not use a pressure washer. If there's enough pressure to blast built-up grease and grime off, I'd say it's too much. I'd use a high pressure hose nozzle, at most (like the things you stick on your garden hose to blast leaves out of your gutters). And aim away from fuse/relay boxes and the like.

Newer stuff should have pretty waterproof electrical connections, but it's still possible you could get water into somewhere you don't want to. The engineers are only thinking about water spraying up from the bottom (and more and more modern cars have plastic trays covering some or all of the bottom of the engine bay). Not the engine getting blasted from the top...so you could find a weak spot that normally wouldn't be an issue.

Also, if the car's been running, I wouldn't wanna blast cold water onto the exhaust manifold, especially if it's cast iron.
 

HeXen

Diamond Member
Dec 13, 2009
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k, i'll do that. i always hated having older cars where the engine bay was so heavily grimed up that even the best cleaners were helpless. I'd rather do it when i wash the car.
 

disappoint

Lifer
Dec 7, 2009
10,137
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Get this:

41mb7flixkL._SY450_.jpg


It's the Nelson Rezimar Easy Clik Seven Pattern Spray Nozzle with Flow Control 50130. $12 on Amazon.com

It has a setting called Mist. Spray Simple Green all over the engine bay (Don't forget the underside of the hood) Then use the mist mode of this sprayer to rinse it all completely. Covering the alternator and other exposed electrical equipment is recommended but not required. Do it when the engine is cold.

http://www.amazon.com/Nelson-Rezimar...868916&sr=1-11
 
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nerp

Diamond Member
Dec 31, 2005
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Just do it by hand, don't blast water on the engine, especially if it's newer. There's a reason modern cars have splash guards and panels under the car and in the engine bay to prevent water getting in. Use lots of rags and some simple green if you have to. I've seen too many people introduce all sorts of problems by spraying water into their engine bay.
 

phucheneh

Diamond Member
Jun 30, 2012
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Just do it by hand, don't blast water on the engine, especially if it's newer. There's a reason modern cars have splash guards and panels under the car and in the engine bay to prevent water getting in. Use lots of rags and some simple green if you have to. I've seen too many people introduce all sorts of problems by spraying water into their engine bay.

Actually the plastic beneath the engine is more for aerodynamics. Older cars are actually far more succeptible to issues from 'washing' the engine...very easy for water to get under the distributor cap, or into other places where it shouldn't. Modern 'weather-pack' style connectors trump the hell out of old spades and whatnot.

Not that I'm disagreeing with 'don't do it' or anything...just sayin'...
 

nerp

Diamond Member
Dec 31, 2005
9,866
105
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Yes, you're right about the aerodynamics. Newer cars are a lot better about where rain water is directed under the car and the wheel wells, though and I have a suspicion that the more covered-up our engine bays are getting, the more electronic bits are showing up in places they otherwise wouldn't.
 

yhelothar

Lifer
Dec 11, 2002
18,408
39
91
My experience with spraying down the engine is that sometimes water gets into the spark plug wells. This sometimes keeps the engine from starting, or from running on all cylinders if not all of the plugs gets filled with water.

So just check your plug wells and make sure they're thoroughly dried before you start your engine.
 

phucheneh

Diamond Member
Jun 30, 2012
7,306
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My experience with spraying down the engine is that sometimes water gets into the spark plug wells. This sometimes keeps the engine from starting, or from running on all cylinders if not all of the plugs gets filled with water.

So just check your plug wells and make sure they're thoroughly dried before you start your engine.

For clarification: he's talking about engines with the spark plugs going down into the top of the cylinder head...what are modern 'hemis,' basically. Though combustion chamber design varies greatly, I think you could call modern heads "hemispherical"...if for no other reason than four valves per cylinder pretty much requires it.

This is opposed to your general 'wedge head' setup, where the spark plugs go in closer to horizontal. e.g. some modern V8's, mostly older V6's and I4's, and of course all of your old 'muscle car' V8's aside the from the aforementioned chrysler 'hemi.'

The latter, you don't have to worry about, really. The ones that go in at the top will have cylindrical wells that pass through the valve cover. There will be kind of an 'umbrella' on the top of the long spark plug boot, which generally seals moisture out...but it's not meant to take even a pressurized garden hose blast. Similar problems are had when the seals between the plug wells are the valve cover are bad, and they get filled with oil. I'd imagine water would be worse.

Nothing should really leak into the engine, though. To get past the crush washer and then threads of the spark plug is a difficult task. I've seen them get oil fouled eventually, though...or maybe that's just because a bunch of oil fell into the cylinder and ran down the plug when i took it out. ;P Your risk is misfires because the spark 'pulse' is using the moisture to find ground before the gap of the spark plug.

This applies to coil on plug as well as distributors.

Again: Simplest response is "no, don't pressure wash your engine."

If it's that dirty, anyway, I'd recommend just pulling the damn thing and cleaning it out of the car while you do a regasket (and possibly a total rebuild, if you fancy). That grime is actually forming a barrier to help keep actual, useful oil from seeping out through your shitty gaskets.

edit: god fucking damn I can write a lot about simple shit. I just thought 'spark plug well' might not be a familiar term to some, especially if they've got an older engine.
 
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bruceb

Diamond Member
Aug 20, 2004
8,874
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Do not use very high pressure and keep water out of the distributor (if it has one) and out of the alternator and throttle body. Let completely dry before attempting to run engine after it is done.
 

HeXen

Diamond Member
Dec 13, 2009
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might be hard to keep water out of the Altenator as it sits kinda low.

013swz.jpg
 

thescreensavers

Diamond Member
Aug 3, 2005
9,930
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Cover Electrioincs like MAF/alternator and others with Alluminum Foil, mist your engine bay. Spray Simple Green, scrub everwhere. And now rinse.

Done
 

Howard

Lifer
Oct 14, 1999
47,989
10
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For clarification: he's talking about engines with the spark plugs going down into the top of the cylinder head...what are modern 'hemis,' basically. Though combustion chamber design varies greatly, I think you could call modern heads "hemispherical"...if for no other reason than four valves per cylinder pretty much requires it.
I don't think anyone uses true hemi combustion chambers anymore. Just way too inefficient.
 

Railgun

Golden Member
Mar 27, 2010
1,289
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The short answer is no. If you know what you're doing you can wash it all day long. I've power washed too many engines to count without a single issue.

Be smart about it and you're fine.
 

phucheneh

Diamond Member
Jun 30, 2012
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I don't think anyone uses true hemi combustion chambers anymore. Just way too inefficient.

I just meant there's a general dome shape that supports that 'plug in the middle with four valves around it' setup, as opposed to the older shapes that were used to try and spread the flame front effectively when the plug is coming from the side(ish).
 

exdeath

Lifer
Jan 29, 2004
13,679
10
81
Modern design is called pent roof combustion chamber. Vastly superior to true hemi.

As for getting the engine wet, keep in mind that it gets wet all the time. Various fluids leaking, rain, condensation, dew, etc. It sits in an abusive outdoor environment all the time and design considerations for connectors, sensors, and such take this into account. You don't need to have the car in a clean room to open the hood. :awe:

I've had radiator hoses bust and douse a factory alternator with 180k miles on it, it's fine. It's just some enameled wire loops, water isn't going to hurt it. I'd be more concerned about the bearings more than anything electrical and those are sealed as well.

It's a crude 100 year old internal combustion engine, not a hard drive.
 
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phucheneh

Diamond Member
Jun 30, 2012
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'Pent-roof' is definitely the word I had forgotten about.

And agreed on the alternator. I didn't want to outright say it...but I've doused hundreds of alternators. Usually just rinsing stuff after a cooling system repair. A lot of the time, there's a massive air bubble I'm trying to bleed and the radiator throws up all over everything.

But again, that's just pouring water over the engine. Often while running (don't hit the belts, you'll go deaf). Pressurized water can do different things.
 
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Jun 7, 2015
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Many useful tips! Thanks guys!

Bumps old thread? Check. Bumps other old threads with similar topics? Check. IP from country known to have a significant number of spammers? Check. Sorry.
 
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JulesMaximus

No Lifer
Jul 3, 2003
74,456
854
126
Man, I've been driving for over 30 years and I've never power washed the engine of any car I've ever owned.

Do you spend a lot of time looking at the engine of your car? I've probably opened the hood on my current car 3 times in 2+ years.

Not sure what the point is quite frankly.
 

pauldun170

Diamond Member
Sep 26, 2011
9,133
5,072
136
It doesn't hurt the engine as long as you disassemble it first.

Man, I've been driving for over 30 years and I've never power washed the engine of any car I've ever owned.

Do you spend a lot of time looking at the engine of your car? I've probably opened the hood on my current car 3 times in 2+ years.

Not sure what the point is quite frankly.

I almost hit the like button to this comment until...
1. I noticed there is no stupid like button here
2. I did a go all Mr. Clean on my Kawasaki back in 2012. Figure I'd make it all pretty ahead of its 20th birthday.
 

jlee

Lifer
Sep 12, 2001
48,511
219
106
Man, I've been driving for over 30 years and I've never power washed the engine of any car I've ever owned.

Do you spend a lot of time looking at the engine of your car? I've probably opened the hood on my current car 3 times in 2+ years.

Not sure what the point is quite frankly.

That's because you drive appliances. :p