I clean off my engine about 1 time every two weeks with a rag and windex but some places that are deep and cracks I cant get. Is it alright to spray it off with water, Or does water make anything under the hood rust. Thanks.

 

You'll be fine, just put a rag over the distributor if you're paranoid, and if you have a carb leave the air cleaner on.

 

I would avoid using high pressure water (i.e. carwash) to clean the eng. compartment. The water makes it way into the various electrical connectors and causes corrosion.

I don't clean my eng that frequently, but when I do, I use mineral spirits (cold eng!) with a venturi-type chemical sprayer.
It won't hurt anything, works well, and dries pretty quick.

 

Yeah, I just use running water as well.

 

For the really dark, deep, skanky recesses of the exterior of the engine, I've had good success with a liquid laundry detergent concentrate thinned with a little water. Use a stiff parts cleaning brush to apply the thinned liquid, allow it some time to work, then break the deposits loose with the brush while adding a bit of warm water. When you have a nice, greasy splooge of a mess on your engine, rinse off the soap and debris with a sharp stream of water from a garden hose, then attack any remaining spots. It may take several attempts to get the really tough buildup, but it will eventually clean up.

If you get a really baked-on deposit, a mineral spirit or kerosene will break up the crust effectively, followed by the soap cleanup. Just be aware that the solvents are flammable and can stain conrete or soften asphalt. The beauty of a laundry detergent is that is won't harm the plastics or rubber, won't etch the aluminum parts as some harsh cleaners can, and rinses off the driveway or garage floor without leaving an oily mess behind.

If you are concerned about wetting the ignition or fuel systems, tie a plastic shopping bag over the distributor with a rubber band and cover the carburetor or TBI throttle body with an inverted coffee can or appropriately sized container (cut off the top of an empty plastic windshield solvent bottle). Everything else shouldn't be harmed by the water/soap mixture nor the rinse.

Incidentally, the engine should be moderately cool before you perform the cleaning.