Confession time!
I power washed the engine compartment on mine with no ill effects. Done it on several other cars too. But my power washer is an industrial Karcher (ex hire company gone broke) with adjustable pressure and a maximum volume adjustment on the trigger. Turned right down it has little more oomph than a hosepipe but the actual wetting position is very controllable although swinging a 4 ft (ish) double lance with separate suds & water feeds can get cumbersome. But for £15 back in 1985 or there-abouts I wasn't complaining.
Didn't one of the detailing masters on here reckon a hand held steam cleaner worked well?
One day I shall make me a Haralson pressure multiplying hose end just to see how well they do.
Clive
PS Dyson. Over-rated, overhyped, badly engineered and, frankly, not very effective. Had one. Got fed-up with fixing it every couple of years and scored a cheap Kirby out of the local free ad paper. Also seriously overhyped and (way, way) overpriced but effective and built like a battleship. Fixing Dyson "Its just stopped" cleaners was easy money for a while but when one comes back for the fourth time 'cos James D can't design a cable clamp it got bit too old. James D is in the same category as Clive Sinclair and Alan Sugar all mouth, no trousers and a convincing line of patter to cover up incompetence. Ball-barrow was the only good idea James ever had. Even then he couldn't get the centre of gravity right managing to produce a wheelbarrow that is almost impossible to tip for emptying. Which is pretty hard to do!