You need something like this Hotsy.
hotsy hot pressure washer 555SS $1000 or b/o
This would be a nice little unit to keep things nice and clean.
I have over the years used the Steam Cleaner at work we used on the trucks, tractors, PU`s, cars etc... I would do our MB`s and my PU every so often to keep them clean. I never worried about getting anything wet, and never had any problems.
I ran the front end up on ramps, and then did the bottom side first. then would do the top side of the engine last. blasting the bottom always blows stuff up on top. then do the top and wash it all down getting into all the nooks and crannys. just don`t hold the pressure in any one place long.
Charlie