First Compression Test

[x98awddsm]

just got the car back from getting its first compression test here are the results.

#1 150 #2 130 #3 140 #4 150
the tech told me the compression in #2 was kind of low but the car is running fine. any ideas of what i can do to fix this? Thank you

 

[ShadyGST]

how many miles?

 

[JusMX141]

They're all a little low for a 2G in my opinion.

My buddy's '95 TSi w/ 138k on the stock 7-bolt reads 180, 182, 178, 180.

 

[clockworktoy]

2G (95-99) T/E 2.0L 4G63 Turbo engine
Compression ratio 8.5:1
Standard compression 178 psi
Service limit 133 psi

Taken directly from vfaq

 

[1gDSM4g63]

Each car's compression is different. 150s is fine although you have to look into the 130. Maybe head gasket, piston ring, etc... Do a leak down test.

 

[Splitpi]

Compression is below service limit on number 2 and out side the range of variance from the high #1 and # 4. I would just keep an eye on if you are burning oil and what not. If the car feels fine, then I wouldn't worry too much. If you plan on keeping the car, save up for a rebuild that will include honing the cylinder walls, new rings and valve stem seals and sleaves.

 

[talonalex92]

My car has 130k on it, compression was 140 all the way across. I burn no oil at all, and it runs vary strong.

 

[KelTsi90]

I think that's low. Mine have 2g pistons and is 180 across. You can try putting a cap of oil in each cylinder. then check it again.

 

[98 Mits GS-T]

I agree with the last comment. Put about 2 drops of oil in #2 and try the test again with all of the spark plugs out. It should stay the same if everything in that cylinder is in sound condition, if the rings are worn then the oil will help them seal and the compression will go up.

 

[x98awddsm]

thank you everyone for your replys. A lil more info on the car, she only has 102K on the motor and is prety much stock, i dont even red line it because i still have the t-25 on so there is no point. really think i need a rebuild already????

 

[JusMX141]

Rebuild? No.

I'm willing to bet your valve seals are leaking, causing oil to seep down the valve stems which is crystalizing on the seating area of the exhaust valves, causing them to not seal properly. This is quite common on DSM engines with over 100k. The car is still 100% driveable, but you ARE losing power from the low compression.

A way to diagnose this would be to pull the exhaust manifold away from the head, and peer into the exhaust ports with a flashlight. If ANY of the exhaust valve stems appear wet, you have your answer.

If this is the problem, the only cure would be remove the head, remove the valves, clean them VERY well, lap them back into the head to insure a good seal, and install new valve seals. This would also be a great time to install ARP studs and a new head gasket.

 

[JStrateger]

My stock 7-bolt I just bought has 150 on all four cylinders, I was told it has around 40-60k on it, mine seems to run alright.