4ZZS

Armor-All - NO
Most Aerosol Cleaners (Gunk, etc.) - MAYBE
Simple Green - YES
Read the Armor-All bottle cautions about what NOT to spray. The silicone in it will make things slippery, so DO NOT get it on the belts. As stanggand1892 just said, it is nice and shiney but it collects more dust.
The foaming spray cleaners work pretty good but some of them make your engine compartment stink for days.
Simple Green is great for cleaning the entire engine compartment. Hoses look clean and good, but not shiney. I spoke with the Simple Green guys at the SEMA show last November. They said the most cost effective way to use their product is to buy the "Regular" strength juice and dilute it 1:1. When using it under the hood, mist the entire engine down with water, spray the Simple Green all over, wait a minute or two and hose everything down. Get the engine running and keep on rinsing with water. Obviously, spray lightly around all electricals. Make sure you thoroughly rinse the hood, fenders and windshield with water. Keep the engine running and if you have an air hose, use it to blow the standing water out of all the low areas (Engine Block, fuse boxes, etc.). Take an old chamois or towels to get rid of any water spots. This won't collect the dirt as fast as if you use Armor-All.

GTBILLY

hey man u can look on my profile at my engine best thing to do is go to the car wash LEAVE YOUR CAR running and pop the hood and spray it off real good after that go home and maybe take a rag and wipe what u can down this will make a big differnce thats how i do mine and mine stays clean PS when your washing they have that engine/tire cleaner

Mt Twigbert

Use any good engin cleaner.. Go to any auto parts store and you will find it..

Spray it on and use a brush.. Yes, using a brush is key for the caked on stuff.. Something similar to a toilet brush to get in all the nooks n crannys.. Then hose it down.. It make take 2 applications to really clean it up.. I've done it many of times to my engines and am yet to have any problems.. Just don't use alot of water pressure.. Thats why you want to use a brush..

2000STANGGT

I use armor all wipes too, but I just have to wipe the dust off my car I hardly drive it. Get some engine detailer at Wal-mart it makes it shine.

dlazrael

I use simplegreen(diluted 1:1, spray bottle) + a garden hose linked to my kitchen sink (don't have an outside spricket) I spray the entire compartment, just don't concentrate on electrical or belts. Then, depending on what Im doing with it, Ill either just dry it off with a towel and armor-all WIPES the plastic parts, or just dry it off. I have done it with the motor on and off, I haven't noticed a difference, really. most of what everyone's said here is pretty good, if you really worry, cover electrical parts + alternator etc with syran wrap.

But, you DO know that if the car is off.... the circut is running the full amperage... reducing the risk of shock....

jlong00

I wouldn't clean an engine while it's running. (I know some people do, and swear by it, I just wouldn't) I always clean my engine while it is off, and more importantly, cold - to prevent the risk of possibly cracking the block (hot engine + cold water = [:'(] ) I usually cover the battery, and the carb (if its carbuerated - i'm assuming its FI)... Gunk Engine Brite is pretty good stuff.. Just let the motor cool, spray it on - wait 20 minutes and hose it down. You may need a brush depending on how bad the crud is caked on.

06mustang88

that's what i always thought. why do people do it with the engine on? what does that help?

Sebski

Gunk.. forgot the specific name, but heat up the engine TURN if off. spray it on scrub lightly then use little water pressure and rinse off. Shiney

dlazrael

same idea.... thats why i do it off from now on.... that and completed circits with running energy (volts/amps) + water = a shcoking expierance....

Wouldn't you be more likely to damage your car or injure yourself with running water, conductive chemicals and electricity? Or did we all not pay attention in 6th grade science...

70 MACH I

Just be careful with coil on plug cars with heavy hose or powerwasher by the individual coils. You can get water down into a plug well and cause a misfire. Other than that, wash away.
John