Re: Compression Testing Procedure
Doing it warm gives you the most meaningful and accurate compression readings. There won't be too much or too little oil that can throw the readings. Plus the parts are mated best at operating temperature.<br /><br />I do it cold for customers unless I want to compare readings from warm and cold. Time is money and warming up takes time. Cold readings still give you good enough information. If time isn't an issue, do it warm.<br /><br />The extinguisher is in case the motor has gas in the cylinders which can spray out and ignite from a sparkplug. It's rare but certainly possible.<br /><br />I take it your motor doesn't have a telltale. The water won't come out of the holes on the back of the motor when you're on muffs. It needs exhaust back pressure from being in the water. You can probably install a telltale. Many Chryslers and Forces have a plugged 1/8 pipe hole in the head. Screw a fitting in there and route some speedometer or aquarium hose out of a rear corner thru a hole you drill in the pan. Definately a worthwhile upgrade.
