I used to detail for a Honda dealership. We leave the car running, spray down the engine and underside of the hood with some detergent, use the camel hair brush (foaming brush in most manual carwashes) and scrub the top of the engine a bit.. then just hose off with a modest amount of water. The reason you leave it running is so that you actually clean all sides of every belt and pulley, and if you keep your ears open, you know when you´re drowning something, because the car will sputter. Also, being warm you don´t need to wait for it to dry.. just let it keep running for a while.
YOU WILL NOT CRACK YOUR BLOCK.. that´s just silly, you know how big that block is and how much cool water from the radiator enters the block when the thermostat opens up? You ever seen land rovers with snorkles?? You think those shoddy engines crack? Hell no. Just don´t dedicate yourself to soaking down your exhaust manifold and you shouldn´t have any problems. And yes.. sheild any cone air filters unless you like the idea of your engine ingesting some un-compressable water.. say goodbye to your pistons rods and crank.
PS, some notes on that foaming camel hair brush at the carwash (don´t use the nylon POS brushes, don´t even visit those carwashes) :
- Soak down your car with soapy water.. no use rinsing it with fresh water right away, you´re paying for every gallon (minute), make it count.
- Once you´ve gotten the car completely wet, and most importantly, cool, walk over to where that brush is up on the wall and spray it with the pressure washer for a good 10-15 sec to get any sand or dirt the last person left in there.
- Then run back, throw the switch over to the foam brush. Use the brush in a back and forth motion on the hood windsheild, roof, backlight and trunk, then move to the side windows. Be rough with it, that camel hair won´t hurt the finish. Don´t go below the level of the trim until you´re completely done with the top.
- After you´ve gotten the sides and the rear, hit the front facia and scrub those bugs off. Now, scrub the hell out of your wheels with the thing.
- Now that the car looks like a mound of foam, throw the brush back up on the bracket like a good carwash patron and start rinsing with the wax.
- Go from top rear to front bottom. The car is designed to shed water from front to rear, and you want to rinse in ever nook and cranny (to hell with sheding). Shoot the hell out of the door handles, body panel gaps, mirrors and the wheel wells.
- If you see any foam towards the rear of the car, move back to that point and move forward again.
- Once all the foam is gone, keep spraying and moving around until you can see the water beading up all over from the wax.
- If you´re doing your engine, you´ll want to do so after you´ve scrubbed the wheels, you´ve already left the hood popped and the engine running, right? Just pop her open and scrub the hell out of the underside of the hood, working your way down until you´re scrubbing the top of the radiator... rinse the engine/hood first then move to the back of the car and continue normally.
This should take you 8-10 minutes depending on how fast you can run around the car... which translates to a couple bucks. Whalla, the best 10 minute carwash in the world.