I agree, you have to know what you're doing with a pressure washer and also let the engine bay have adequate time to dry before starting/driving.

 

My engine bay cleaning/detailing routine is very similar and I am very happy with the results. I cover the alternator with a gallon-size plastic baggy, or small trash bag. I then take my air hose (from garage compressor) and blos any loose dirt/debris from the engine bay (normally just dust). I then take my garden hose with the nozzle set to 'shower' and liberally sprinkle the entire engine bay. Once done, I will spritz the entire bay with Simple Green diluted to a 2:1 mixture. I let it set for a brief time to dissolve any grease/oils, but not long enough for it to dry (as mentioned, Simple Green is no bueno on aluminum). I then use the nozzle, again on 'shower', to liberally rinse the entire compartment. That is followed by a pretty thorough drying session using a couple drying towels (for the uninitiated, there are such a thing. They absorb more than standard bath towels). Once dry, I follow with a the air hose, blowing water out of electrical connections, coil/plug areas, etc. Don't go crazy with the pressure, just enough to move the standing water. I will then give the entire compartment a liberal spray of Griot's Garage Engine Bay Dressing, paying special attention to any 'black' areas. The dressing really makes the black or grey stand out. Let it dry, then lightly wipe with a microfiber towel. Start your car, let it get to operating temp and the dressing will 'set'. Stand back and enjoy your detailed engine bay!

 

A couple of years ago I tore down an engine for a project where many of the components would be replaced. All the parts were removed and set aside. They were filthy.

I was looking for a method to degrease engine and frame components. First I tried soaking some small parts in solvents like Safety Clean and Genuine Safety Solvent 140. Neither of these removed the oil film build up left from heat soak. Then I tried diesel oil, spray can degreaser, break cleaner and just about anything you could get from the local automotive part store. None of them worked, or worked well enough to claim success.

Wondering how to remove the heavy deposits on the pistons I decided to scrape them with a razor blade, but realized quickly this was too dangerous. Then I thought the heavy deposits would come off with a brass rotary brush. This too was a fail.

Frustrated, wondering what to try next, I noticed an old pump spray bottle of 'Simple Green'. So I sprayed it on some of the steel internal components and the oil deposits just wiped off with very little soak time. I was shocked! Then I sprayed it on one of the rods and it too cleaned up very quickly.

So I made up a soak bath and filled it full of Simple Green concentrate, and placed four of the piston rod assemblies in to soak overnight. The following morning I was able to clean them all with a light scrub from a soft bristle nylon brush.

My point is, Simple Green is good stuff.

Below are photos of parts, before and after cleaning.

On the clean piston photo you can easily see the scratch marks left from the rotary brass brush. Then you can easily see the result of the Simple Green soak. The line across the piston indicates where one side of the piston received more soak time than the other. Regardless, SG did a wonderful job cleaning the piston, the rod, the rings and the ring lands; all with very little effort on my part to bring them to the condition as shown.

A number of the guys here have suggested Simple Green, ALONG WITH A METHOD for use in the engine bay.

If you want a clean beautiful engine bay there is no need to look further than this thread. Simple Green, along with the final top coating and the methods described here, JUST WORK..


Before cleaning with Simple Green


After cleaning with SG


Internal oil pan before


Internal oil pan after




Other internal parts cleaned with SG

 

Yessir, the stuff (Simple Green) works! Just don't let it dry on your aluminum parts or it WILL remove the finish.