P21S Total Auto Wash works great on engine bays. Steps are really quite simple but before the steps it's important to note that depending on the year of the vehicle you'll be required to cover sensative areas of the vehicle. What I mean is that if the vehicle is a brand new model (2008, 2007, 2006..ect..ect) then you shouldn't really need to cover too much areas, maybe just the air intake and the alternator if you can see it that is. If the vehicle is an older model vehicle, then you'll need to cover the spark plugs, alternator, air intake and well any other parts that are exposed.
So depending on the vehicle you may need to cover up sensative areas or not....so once you have protected sensative areas (or not) you give the engine bay a quick rinse, then spray P21S Total Auto Wash. Let it sit and works it majic for several minutes. Then agitate with a brush, you can repeat the process and apply another coat of P21S Total Auto Wash but becarefull because P21S Total Auto Wash goes by quite fast, before you know it it's all gone.
Any who, that's what I do hope this helps
