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KL03
09/19/2003, 01:39 PM
So I finished my first bottle, and decided to do a compression test to see how well it held up. My car also has 142,000 miles on it. The engine was cold, the car sat two days before I did this, so it may have effected it but these are the numbers I got,

150, 140, 150, 155, 150, 145
________
rolling a joint (http://howtorollajoint.net/)
Splat
09/19/2003, 02:18 PM
I'm not familier with compression so this means nothing to me... a little explanation?
Eric94GT
09/19/2003, 03:14 PM
Those are pretty good numbers. You may want to check it again after another bottle to see how that cylinder that got 140psi is doing.
Eric94GT
09/19/2003, 03:20 PM
Originally posted by Splat
I'm not familier with compression so this means nothing to me... a little explanation?

A compression test is to see how the internals of your engine are doing, mainly the valve seals and the piston rings. First thing you do is pull the fuel pump fuse and disconnect the distributor. Then one by one you put the compression tester ($30 at Checker) in the place of a spark plug and turn the engine over for one second three times. The tester will then show how much psi the cylinder created during the times you cranked it over. You want all the numbers to be close to each other and if they are that means that all the cylinders are wearing evenly which is good. If you have a cylinder that is showing a lot less psi than the others than you may have some sort of seal or ring problem and you might want to bring it somewhere to have a leakdown test done to see where exatly the problem is.
Splat
09/19/2003, 03:31 PM
I know what compression does and how to test it. But I don't know if 140-155 is a good range. It could be 75-100 and I'de be asking the same question.
MN Probe GT
09/19/2003, 03:33 PM
on a brand new PGT it would probably be around 190psi.

mine ranged from 150 to 180.
naustin
09/19/2003, 03:44 PM
I need to do mine. My car burns alot of oil. But I don't think it's the rings. I thin k its the valve seals. :shrug:
jay
09/19/2003, 03:45 PM
i think that anything below 130 is abnormal.
KL03
09/19/2003, 03:54 PM
Do you think that my numbers would have been a little higher if the engine was hot? Cause the cylenders would heat up and expand and such
jay
09/19/2003, 03:56 PM
heat causes things to shrink.. not expand... its okay to do compression on hot engine, you can find out if you have any
BLOW by in the cylinders... but its recommended to do it after a 2 to 3 minute start up from cold.. then do a compression test...
Splat
09/19/2003, 04:05 PM
Originally posted by naustin
I need to do mine. My car burns alot of oil. But I don't think it's the rings. I thin k its the valve seals. :shrug:

This shouldn't matter since your BUYING A NEW ENGINE
Eric94GT
09/19/2003, 04:38 PM
Originally posted by Jay Mayes
heat causes things to shrink.. not expand... its okay to do compression on hot engine, you can find out if you have any
BLOW by in the cylinders... but its recommended to do it after a 2 to 3 minute start up from cold.. then do a compression test...

:smokin: What are you smoking? Heat makes the aluminum of the engine expand. It's probably fine to do the test but be careful of stripping things because the spark plugs will be hard to crack loose.
naustin
09/19/2003, 05:43 PM
Originally posted by Splat
This shouldn't matter since your BUYING A NEW ENGINE

Well Yeah, I know.. But not for awhile. ;) But I might keep the old one and rebuild it into a turbo motor.... So it would be nice to know.

My basement could be the MNPOC indoor, heated, engine rebuilding shop.... Who wants to donate tools?
matt
09/19/2003, 05:58 PM
Originally posted by Jay Mayes
heat causes things to shrink.. not expand

ruh roh, looks like someone failed 8th grade chem.
tracer bullet
09/20/2003, 10:20 AM
Heh, yeah, he must have had a "brain fart".

Nick, you likely do have a vlave seal problem, it's more common than rings in general, was in fact beginning to happen on my PGT as well, and - if you get a little puff of smoke in the mornings on startup you can be certain of it. Oil dribbles past the seal, between the valve and the guide, and sits on the piston until you light it off the next time the car starts.

Props to Eric for a good explanation of compression test! Not that I'm surprised, just sayin good explanation!