| Author | Topic |
|---|
I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
|
|
Re: What is a compression test?
|
Wed, 06 November 2002 11:32
 
|
 |
A comp check is done to check the integrity of the cylinder seal....in other words to look for wear.
Spark plugs are removed and a comp guage is placed/screwed in the spark plug hole. The engine is cranked over usually with WOT and after a prescribed period of time (usually 10 or so revolutions), a plateau value is reached. This should fall within certain values as dictated by the manufacturer. This process is repeated for each cylinder.
The values should all be within a specified range....if one or more is well outside this range, then the engine should be opened and the cause determined, or not bought/returned. Wet compression can also be checked on a dodgy cylinder....basically oil is squirted into the cylinder (it temporarily aids in sealing the suspect cylinder) and if there is a significant improvement, then it suggests ring + bore wear. You can also do what is known as a leak down test. I won't go into it but it can give a better idea of where the motor is losing compression.
This is by no means definitive, and I suggest you read up in greater detail. No idea what a mechanic charges to do this.
|
|
|
