On my Scenic Cruiser you remove the mattress, disconnect the two shock absorbers and lift the plywood that supports the mattress all the way up and out of the way. Then you have the box and the cover is held by long screws. Some are hard to find because they are sunk into the carpet, remove them and the box cover will come off. The top of the engine is exposed and you should be able to do what you want. That is a good time to get a electric power washer and after you have sprayed the engine, CAC and radiator with Simple Green or a degreaser, then after five minutes spray the whole thing clean. I actually start the engine and let it run while I am spraying since I have a rear radiator, the fan pushes the water and degreaser right through the fins and the engine will like new. Then just do the reverse of uninstalling and install the cover back. To remove the long screws use a power cordless power drill, it saves you a lot of work.
2002 Gulf Stream Scenic Cruiser
2018 Buick Envision Essence
Neway Freightliner chassis
Aventa II Blue Ox