My Karchner pressure washer. Used it on my 90 legacy starting in 2000, then the 2002 and now the 2004. Do it twice a year, when getting ready for winter, and again in the spring to get rid of all the under hood / chassis salt.
I was always told be carefull about washing the engine in the winter. Soaking all the gaskets and letting them freeze at night could mean trouble. I have never heard of anyone bothered by this, but it does make sense to me. (Assuming it gets real cold)
I suppose you could run your engine or drive it around for awhile to warm everything up and essentially dry the gaskets.
The pressure washer doesn't get anywhere near anything mechanical in my household! Bearings, seals, electronics can all be damaged with a pressure washer.
FYI, there are bearings and seals on everything that a belt is connected to in the engine bay.