Drive the car around until its at full operating temperature. Go to the car wash, whip out a bottle of Simple Green, cut the sprayer onto "stream", and go to town. Spray everything down, minus the alternator, distributor, and anything exposed (air filter, wiring). Let it sit for about 5-10 minutes, then go at it again, soaking it all down once more. Cut the pressure washer to rinse, and spray it down.

Works like a champ. I do it every other time I wash my car, since it was new. I have 91,000 miles on it now, it looks like I have 10,000.