YUP, I'm an old street racer from the '60's. Now have a 2011 Prius IV and thought it would be fun to see what kind of answers I would get about: How do you clean the engine in a Prius? We used to spray GUNK on our V-8's, then hose them off with LOTS of water and then run them to dry off the excess water. HOW NOW ????
A clean engine is a happy engine. But the owner's manual on the C says it is fraught with danger. I used to keep all mine squeaky clean, but not any more since there isn't anything there to really show off any more. "Wow! Those are AWESOME covers, rubber hoses, and pipes! Sweeeet!" My motorcycles and mowers still get the treatment, though.
Ever since the 2000's, I quit cleaning engines. First of they don't leak and have a greasy mess any more. Second, there are way too many sensors, wiring, etc. A cleaning would probably do more harm than good.
Hosing toxic hydrocarbons into nearby streams is just something I don't want to do. Same thing for those intake manifold cleaning services: just pumping raw fuel into the atmosphere. I'd suggest to just brush and vacuum if you want, use a brush to help loosen the dust, then switch to blow to knock leaves and junk out of the corners.
The dealer used Gunk on my engine this spring when they did the IM T-SB. Its clean but looks old now.
I use soap and water on my engine. All of the electrical connections are sealed so need to worry about getting them wet. I would never use a power washer on the engine but a garden hose is fine. I have been doing this for over 3 years now and not one problem!
Back in the day- I used to use Gunk Foaming spray periodically on my cars, but I wouldn't dare use anything on today's engines with their complex wiring, sensors, etc... unless it was a real mess. The Gem III Prius has under body covers too- so it seems to keep the engine compartment quite clean without any user intervention. And like Jonny Zero mentioned above "they don't leak and have a greasy mess any more".
Today's wiring, sensors and connectors are far better sealed than they used to be. Just don't go overboard with high pressure. Since modern engines don't normally get oily anymore, a soaking with mild detergent and gentle rinse does a good job if you are so inclined. That said, my Gen III is 2 years old and the engine hasn't been washed yet. It's not very dirty either.
Nobody hoses down engines anymore. To much electronics and cops are easily damaged. They use steam now if you want a professional detail. Have for years. I like my engine greasy. No rust anywhere.
