Honestly the BEST way to do it is to just remove it and than tape the end of the tube. Don't forget to use some tin foil on parts like the alternator, etc. If the motor compartment doesn't need a full on wash than don't do it. Once you do it it's very easy to maintain it. There is a risk when cleaning the motor considering how many electrical connections there are. When I do have to I make sure I cover things like previously mentioned, as little water as possible, and as soon as I'm done I use a backpack leaf blower to dry it. Others want to either keep the motor running, wash on a hot motor, or turn it on immediately after and I disagree with all of them. I use the blower and still let the motor sit until the next morning before starting it. I've got a 100% success rate doing it this way on TONs of cars.