I was just thinking about cleaning my Engine Bay today, I think Im going to use a air hose first to get rid of the bugs and loose dirt etc. then Im going to go over each plastic part with son of a gun or something like that then dry it down with another cloth but spray the Son of a gun on a rag not on the engine or other parts, it mite take a little longer but it shouldnt hurt anything this way, no replacement for good old elbow grease. besides that it leeves a lot of time for thinking of what your focus could turn into with a little time and money.
I wouldn't do it on a Hot engine... just think, hot metal, cold water = crack? Not sure, but not something I'd like to find out the hard way
I've cleaned the bay a few times, I've never used degreaser though. My engine really doesn't have a lot of "gunk"... it's just dusty/gritty, so i find water and some selective Simple Green to do just fine.
At home, I just pull the car into it's "bath space", engine on maybe 20 sec, so it's plenty cool. When I have to do a DIY-bay wash, the bay is within 5-10 min from my house, so again not like a 20 min highway drive. I generally save the engine for last, either way, so I'm sure it cools some.
I have a Duratec, so your Zetec looks different. I've never covered up anything either (I could be a terrible role model?) My CAI filter is mostly protected under the fender, and I avoid directly spraying the coils-on-plugs on the valve cover area.
At home, I like to rinse off the bay with a hose, without a nozzle on it... that way you don't get the "collateral spray" all over the place, seems more accurate? I give everything a brief rinse (except the filter/coils) and then get into the nooks and crannies with an old toothbrush, shop/paper towels, rags... whatever I have with me that day. Then I apply some SG to the particularly yucky areas (my valve cover generally looks grody) and scrub that with a rag, and rinse.
At the carwash bay, it's a little more annoying, since there's no spray control. I put the sprayer on regular water (no soap or "engine clean foam" setting - nasty). Then same deal, just try not to drench the questionable parts. A real quick spray though, is probably no worse than driving in a downpour, the engine gets pretty wet in the rain, so I try not to freak too much. Just don't deluge the whole thing, it rarely needs it.
jesus people ive done this hundreds of times. DONT COVER UP ANYTHING! just hose the thing off while its running. it will not hurt a thing! degrease EVERYTHING and let it sit for a second then rinse it all away good until no suds are left. repeat if nessicary.
^^^Not so true my friend. On our Dtecs you have to be sure to cover up the slot in the valve cover where the coil packs go. The seals on the boots aren't that great and I actually destroyed one once by just hosing it all off. Water seeping in with the spark plug and destroyed the coil. Only found out once it started misfiring.
Whenever I detail a client's engine bay, I have the engine running and I go over it first with the hose on one of the brisk fan-type sprays. If I go over something and the engine blips, I just stay away from it with the hose. After that, shut it off, apply some degreaser to loosen up the crud, rinse, and then elbow grease where necessary. As long as you're not blasting away under there with a power washer designed to take the paint off your house, I think you'll be okay.
They make a degrease in a spray can I think it's called "Engine Brite"....mist the engine bay with degreaser.... spray carefully with luke warm water (avoid sparks, air intake, etc.)....use a rag to scrub hard to get areas and dry the saturated areas...and then follow up with a silicone spray to keep the "wet" look. Run engine to burn off the rest of the water.
The belt might make noise when it is wet, but it should stop after you drive a little and it dries up.
I clean my engine almost every time I wash the car. I spray it down with simple green, hit any particularly dirty spots with a stiff brush, then use the garden hose to rinse it off. If I happen to be at a DIY pressure wash car wash, I just go to town with the soap then rinse. This is what I have done on hundreds of cars and my own vehicles, and I've experienced problems only with the DOHC v6 engines in ford taurus and escapes.