Back compression judgement by air blowing out from dipstick well

OPTRALOVER

MEMBER
2007 CHEVROLET OPTRA
1.6L
4 CYL
2WD
MANUAL
90,000 MILES

I have a chevy optra 1.6 LS (Petrol) having 90k kms on odo. Recently I got it serviced from a different mechanic than from the one I usually service my car. The mechanic told me that there is some compression loss in the engine and he concluded this by the air coming out of the dipstick well.

But the car is running just fine without any noticeable power loss. I took it to a different mechanic and he told me that air coming out of the dipstick well is because optras have a lower positioned oil chamber as compared to other cars and hence its normal.

I am a little confused now. Kindly assist.

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,708 POSTS

First, any engine will have a bit of compressed air in the crankcase. It is normal from compression bypassing the piston rings. Excessive compressed air could be a problem. However, in your case the engine is running fine.

Therefore, I feel that there is a different issue. On the engine is a valve called a PCV valve. PCV stands for positive crankcase ventelation. The purpose of the valve is to vacuum excessive air from the crankcase and reburn it in the engine. If the valve is plugged or damaged, it will not do that; thus, it will cause excessive air build up in the crank case which will escape via anywhere it can (dipstick tube, for example).

Check that first and let me know what you find. Also, remember it is normal to an extent to have air / compressed air in the crankcase. Excessive air can be a sign of worn engine valves or cylinders.