ok guys, i have a '00 2200 and i pulled it into class last week and did a compression test on it.
mind you, i forgot to hold the throttle open, but i did for all cylinders, so readings should be a little low around the board.
1-140psi
2-120psi
3-100psi
4-90psi
...then i got really nervous...so i did a cylinder leak test.
1-5%
2-6%
3-8%
4-9%
...not much leakage at all
so...why the big range of compression? i don't hear any engine noises, like ticking or anything like that. it HAS to be something in the valvetrain, correct? valve not opening all the way, and staying open too long? maybe a callapsed lifter or 2, or sticky lifter? but wouldn't i hear that? what do you more experianced guys think?
oh, and the engine has 162xxx miles on it...not bad for the leakage huh?
Add a few drops of oil to each cylinder than retest.
No it doesnt "have" to be anything in the valve train, your valve thing about not opening all the way or staying open just shows you have no idea how an engine works, I suggest you visit howstuffworks.com and search "car engine" than you may understand why it doesnt make sense
You would hear a sticky lifter
- 2004 Cavalier - 124k, owned since new
Do it again, start at # 4
When taking a compression test you must have a good battery, all plugs removed and if at all possible disable the fuel system. Pull the relay or fuse.
Your engine may have been cranking slower and slower and slower with each cylinder.
You may have not been doing the same number of rotations on each cylinder
Gasoline was washing the cylinder walls with each test and by the time you got to #4 the sealing oil around the rings was washed away.
Crappy test gauge
Test gauge not screwed in properly or not held tightly against each spark plug hole.
Always retest when you get screwy numbers like this. Each cylinder is down 20 -30 pounds from the previous one, this isn't real life.
Dave
I would redo it again, If it comes out with the same numbers thing its time for a new motor.
Rob wrote:Add a few drops of oil to each cylinder than retest.
No it doesnt "have" to be anything in the valve train, your valve thing about not opening all the way or staying open just shows you have no idea how an engine works, I suggest you visit howstuffworks.com and search "car engine" than you may understand why it doesnt make sense
You would hear a sticky lifter
ok, doucher, i know how an engine works, the valvetrain thing was a suggestion from my teacher(which, if the valve wasn't opening all of the way from a collapsed lifter, not as much air would go into the cylinder, which would mean it wouldn't create as much pressure when the piston reaches tdc...makes sense to me...so far he's been right about everything i've brought to him). i did add some oil to each and retest. one step ahead of you. after oil i got from cylinders 1-4
140
130
120
100
slight increase, but still a large spread. the reason why i didn't post that was since i had low leakage, i didn't think it was too important, and it didn't bring it up enough to not make me wonder whats going on. i asked for help, no need to try to show how high and mighty you are. being condescending isn't helping at all. just cuz i don't understand this, doesn't mean i know nothing about an engine.
i did the test quite a few times that day. i did unhook each injector, and each plug was out. battery tested good before the test, and each test was 5 cranks. thats why i'm confused. i kept doing the tests over and over hoping for some magical new number...but nothing.
i thought the same thing at first about needing a new engine, but then the leakage test just confused me, and idk...i guess since i have low leakage, it makes me more confortable about my engine. hoping its not a false hope...
Well the fact that it brings the compression up about 10% on 3 of the 4 cylinders after adding oil it could be from piston rings, but the leakage past them isnt that significant.
The leakage test, you dont need to know that for the real World, I have never in my life seen anyone use a leakage tester in the real World, and never met anyone that has one.
If the lifter was collasped you would have other driveability issues, besides compression being a bit low.
Your engine is most likely just wore out and some cylinder show it more than others.
By the way, are you getting into the automotive industry,just wondering thats all.
- 2004 Cavalier - 124k, owned since new
When you do a cylinder leakage test it is so much more than just numbers.
One of the biggest things you can find out is where the problem is.
Is it an intake valve? Air will come hissing out of the intake manifold
Is it an exhaust valve? Air will come hissing out of the tail pipe
Is it rings? Take off the oil filler cap, air will come hissing out of the crankcase
Is it a head gasket or cracked water jacket? Air will turn into bubbles and come out of your filler neck of the radiator
Is it a bad head gasket between cylinders? Air will come hissing out of the spark plug hole next to the cylinder being tested.
Sure, the numbers are nice, but as you can see not all that helpful.
Just for fun, run the compression test starting at # 4.
How's it run?
Lack of power
Idle uneven
Have you done the old time test and put a vacuum gauge on it, that will tell you a lot.
There were many tricks of the trade BEFORE engine analyzers, scopes and OBD II !!
dave
david keevil wrote:When you do a cylinder leakage test it is so much more than just numbers.
One of the biggest things you can find out is where the problem is.
Is it an intake valve? Air will come hissing out of the intake manifold
Is it an exhaust valve? Air will come hissing out of the tail pipe
Is it rings? Take off the oil filler cap, air will come hissing out of the crankcase
Is it a head gasket or cracked water jacket? Air will turn into bubbles and come out of your filler neck of the radiator
Is it a bad head gasket between cylinders? Air will come hissing out of the spark plug hole next to the cylinder being tested.
Sure, the numbers are nice, but as you can see not all that helpful.
Just for fun, run the compression test starting at # 4.
How's it run?
Lack of power
Idle uneven
Have you done the old time test and put a vacuum gauge on it, that will tell you a lot.
There were many tricks of the trade BEFORE engine analyzers, scopes and OBD II !!
dave
well, i didn't check to see where the leaking was coming out of, cuz my teacher said not to even worry, cuz the engine had such low leakage, especially for its milage. and lack of power?...have you ever driven a ln2?lol. its the same as it has always been for me...had it since 132000 and it always idled around 600, but varied up to 200 rpm's(so, between 500 and 700), and has absolutely no top end power, but considering it only has 115 hp from the factory, and that was when it was new, i thought that was just fine. it still can reach the limiter, so its not like it doesn't have enough power to get up there anymore...just has very poor acceleration at highway speeds...but again, its a ln2.
i did a few compression tests that day from 1-4 and back again...probably like 4 or 5 times...always the same readings. and that was before i put the oil in. when i put the oil in, i only did one compression test.
is anything starting to get narrowed down yet?
