Does anyone know if its possible to do one when the motor is out of the car?

I was under the impression you were supposed to do it when the motor was warm.

 

you could, but i wouldnt trust it, unless you have an air gun. compression could leak since it turns slow, if you have a bad piston.

 

I have an air gun.

 

compression or leak down test??
you can do either out of the car, for a true compression test... your supposed to do it cold.

 

I want to do a compression test.

Everywhere I've read/heard says to first warm up the engine. When the compression test fails is when you'd (I'd) do a leak down test.

 

yea the engine has to be at operating temp I know for a fact if you really want details on why pmme and i will respond

 

you can do it with the engine out, it wont be as accurate without warming the engine up. however, it will still give you a good idea of what it is.

 

How about you just post here so everyone can see what you know?

Or is it something you can't share with the group o_O?

 

if you tell us, ill tell you secrets that will change your life.

 

To do a compression test they RECOMMEND that it be at operating temp. One trick is to buy a block heater and let it warm the block, then run the test. Or you can run it cold and the reading will be off a little, but not by much. Make sure when you do it that you pull the plugs out of the rest of the cylinders for the ease of turning it over. Only let the cylinder compress 4 times to get a correct, or almost correct in your case, reading.