just use a regular hose, people tend to have problems when power sprayers and pressurized water and the like are used to clean the bay. Just spray it down real good and scrub it with a soft bristle brush. You should be fine.
If you're willing to spend $3-4, head on over to any auto store or place that has an auto section, and buy some engine degreaser. This stuff works great. Just remember to READ THE DIRECTIONS I'm not sure what could happen if you don't, other than vaporization of the water when you spray the parts while they're hot.
When we bought my sis's first used car, it looked great outside, but sooo ugly under the hood. So my dad took some of that stuff out and sprayed it on, and BAM, it looked better than mine.
cover battery, cai (intake) if you have one that is exposed and underhood fuse box with ziploc freezer bags or something that will keep water out, mist engine with hose, spray full strength simple green all over engine, let sit about 2 minutes, hose off, you now have a clean engine!! Let idle for about 5 minutes to remove some excess water :banana: :chili:
I use my Preasure Washer on my engine all the time, never had any problems.
I cover my air intake, and the coil pack, spray is down with a can of Engine Bright when the engine is cool, let it sit for 15 minutes or so, and use the preasure washer on a medium setting, not full blast. Once it's dry I lightly spray the engine with some Meguiar's NXT Generation Protectant, looks great!
I've been doing this on my old '93 Mitsubishi Diamante and on my '98 Taurus at least 3 or 4 times a year. It's never given me a bit of trouble.
I might be too late in stating this but before anyone applies the degreaser (or any other kind of solution to clean the motor) make sure and wet down the hood, fenders and even the windsheild area with soapy water.
And while you are applying your solution and/or spraying the engine clean, make sure not to let the soapy water dry. Keep those areas misted.
When I use to detail cars for a Lincoln-Mercury dealer ages ago, I learned this trick the hard way. There was nothing worse than finishing up cleaning a motor compartment only to see the fenders streaked by the cleaning solution.
I think I have gone over this one before, but, you can do it both ways. The trick is making sure you avoid the important parts (electrical). I use low pressure from the hose and plain ol car wash fro an engine that isn't too bad. For others that are filthy, I use orange blast as well, and a little more pressure from the hose.