If you really want to do the engine cleaning yourself and you don’t want to leave it to the professionals, here are some things to remember:

sample engine cleaner

• Remove the air cleanser or filter and waterproof the distributor and air intake with plastic bags to prevent water from seeping in.
• When using an engine cleanser to get rid of the grease and dirt, make sure you read the instructions of the cleanser properly.
• Keep the cleanser out of the car finish. These can damage the paint and ruin the finish.
• Rinse or hose off the cleanser immediately after it had time to take effect.
• Start the engine and let it idle to dry the parts under the hood.

Info from:

Auto Repair for Dummies by Deanna Sclar

Image from:

http://www.chemical-cleaners.com/catalog/images/engine_cleaner.gif