Confused about compression test results

[5ch15m]

My results were from passenger to drivers side were approximately..
180
180
155
185

I have a 98 gsx with a little over 110,000 miles on it..pretty much stock except intake bov and some metal intercooler piping, small oil leak from the bottom but not more than a drop every few days..doesnt seem to be burning anything and no signs of smoke..i was pretty surprised to see the numbers that high though except on that one cylinder, being almost around 30 under the highest one.. still 155 is pretty high for the mileage? what do you think the problem could be? i figure it is probably a valve or something from the searching i did...also what should i expect to pay for repairs? any help would be appreciated..thanks

 

[Nors]

Just one question, are you doing it at WOT?

 

[5ch15m]

i had a mechanic do it actually today while i had the clutch bled and im not sure if he did or not..i can give him a call later today and check if he did if you think that would make a significant change in that 2nd cylinder

 

[Turbo Talon 111]

just for comparison, I had 180s all the way across at 140,000 miles.

 

[5ch15m]

isnt that really good for those miles? all the other posts i read said they were getting like 150 across at mileage around mine..

 

[Nors]

i had a mechanic do it actually today while i had the clutch bled and im not sure if he did or not..i can give him a call later today and check if he did if you think that would make a significant change in that 2nd cylinder

No it would not but it would affect the overall numbers. I wouldn't worry about making the call. The number really doesn't matter, but the numbers relation to each other matters. Ussually a 15% variance between the numbers is what most people think is border line. Something is definitely going on with that cylinder since it is much lower then the others, since its pretty close to 15% I'd say its your call on what to do. I personally wouldn't do anything just yet and would maybe perform a leak down test to see whats causing the lower number. Just so I would know what I will be replacing in the future (possibly distant future).

 

[5ch15m]

my o2 sensor is also acting up apparently and making my check engine light go off..when i get that looked at i will probably have them do a leak down test..i know what a leak down test consists of, but what do you think id be charged for it?

 

[Nors]

Not sure, probably the same cost as the compression test.

 

[5ch15m]

all right good deal..thanks for the advice..hopefully i can find out the issue and hopefully it isnt going to be too costly haha, ive only had the car for a year and still have had no extra money for mods..just doing maintenance and making sure the engine is in good shape first..

 

[LaN-]

pour a cap full of oil into that cylinder and redo the compression test. it if shoots up really higher your piston ring might not be happy. If it doesn't move much your valves are leaking. If could also be your head gasket, but normally you'd see some type of smoke.

If you have plan for the car down the road you might want to look into starting a build up.

If its the head just swap it with a 1g head. if its the rings, start to build up a block.

If its the head gasket i'd still say swap it with a 1g head, but thats up to you.

Either way as long as the car rides fine and doens't smoke, who cares. Run the bi*** into the ground.


Obviously the first thing to do is to really find out what the problem is.

 

[1g_tsi_awd]

pour a cap full of oil into that cylinder and redo the compression test. it if shoots up really higher your piston ring might not be happy. If it doesn't move much your valves are leaking. If could also be your head gasket, but normally you'd see some type of smoke.

If you have plan for the car down the road you might want to look into starting a build up.

If its the head just swap it with a 1g head. if its the rings, start to build up a block.

If its the head gasket i'd still say swap it with a 1g head, but thats up to you.

Either way as long as the car rides fine and doens't smoke, who cares. Run the bi*** into the ground.


Obviously the first thing to do is to really find out what the problem is.

^^ beat me to it.

But, if you swap in a new head, get a ported 2g head... They have better engineering, so when a ported 2g is compared to a ported 1g the 2g is better. If you aren't doing porting then get a 1g head.

 

[Splitpi]

pour a cap full of oil into that cylinder and redo the compression test. it if shoots up really higher your piston ring might not be happy. If it doesn't move much your valves are leaking. If could also be your head gasket, but normally you'd see some type of smoke.

If you have plan for the car down the road you might want to look into starting a build up.

If its the head just swap it with a 1g head. if its the rings, start to build up a block.

If its the head gasket i'd still say swap it with a 1g head, but thats up to you.

Either way as long as the car rides fine and doens't smoke, who cares. Run the bi*** into the ground.


Obviously the first thing to do is to really find out what the problem is.

Agree... do the wet test prior to the leak down test. Easy enough to do... 10 mins of work.

 

[5ch15m]

yeah i agree..i figure ill just deal with it unless it gets worse..or unless its a cheap-ish fix..ill probably do a leak down test..the mechanic said he figures the reason is one of the valves leaking also..but that was just his guess..anyone know about the price that would be to fix? i know the valves themselves are like 20 dollars but im sure labor will be a lot..

 

[1g_tsi_awd]

Do it yourself! Fun learning experience.

 

[5ch15m]

totally would if i could haha..definitly not experienced enough yet though

 

[Splitpi]

totally would if i could haha..definitly not experienced enough yet though

All you need is a compression gauge, a spark plug socket, a socket wrench and 20 minutes of your time. This is not a difficult thing to do.

And if you want to learn... there is no better way than trying.

1) Pull the spark plug wires from the spark plugs (remember which goes where).
2) Remove the spark plugs
3) Disconnect the Crank Angle Sensor (this stops the injectors and spark)
4) Connect the Compression gauge to a Cylinder
5) With the gas peddle floored, crank the engine for 3 seconds.
6) Record the gauge reading and move it to a different cylinder
7) repeat steps 4-6 for all cylinders
7a) If a reading is off, then pour 1 cap full of oil and repeat the compression test and see if the value raised.
8) Reinstall the spark plugs. You don't have to torque them too tight... just a bit more than snug.
9) reattach spark plug wires
10) reattach crank angle sensor
11) Remove the negative terminal from the battery for 1 minute then reinstall (to clear CEL)

Note: If you poured oil into the cylinder, it will smoke alot for a few minutes... don't worry... it will go away as that oil is burned off.

 

[5ch15m]

i was talking about my inability to fix a valve problem actually, haha..i could probably do another compression test myself if i had the gauge..ill pick one up soon and do a wet test to see if its a ring..if that doesnt help i might just live with it for the time being..155 is still pretty good even with the variation right?..it could have been a bit higher also if he didnt crank it long enough, correct?

 

[Splitpi]

It is drivable... but out of spec. But I'm in the same boat as well with one cylinder being out of spec on compression. Mine I believe is ring related. But I don't burn oil and it runs good, so I ignore it till it starts to be an actual problem.

Just keep an eye on it.

 

[5ch15m]

yeah if my car starts acting up ill pretty much have to, the only thing that ive noticed is that it takes a couple more turns to start..beside that the engine seems to run like new and i havent had any problems since i got it..the transmission on the other hand i will never figure out..haha..that reminds me i should probably start a thread on that..

 

[flashburn02]

You seem to have made up your mind but just so you know, I had identical compression results on my TSI and I ran a 14.2 no problem. So don't worry about it, just keep looking for oil in your exhaust.

You could sea foam it??

 

[spyderturbo007]

totally would if i could haha..definitly not experienced enough yet though

It's very easy and would be a great thing for you to start with. Here is a walk-through with pictures.......I like pictures.

 

[5ch15m]

all ready sea foamed it actually awhile ago..helped a lot it seemed..also thank you to the other poster when i go to do the wet one (when i have time, haha) that should help me a lot