Compression Test Result

[Pasteurised]

Hey guys, did a compression test on the S3, results:
Cylinder 1 195
Cylinder 2 155
Cylinder 3 190
Cylinder 4 195

Obviously there's an issue with Cylinder 2.
While performing the test on Cylinder 2 there was a loud pop noise, this did not occur on other cylinders. Any idea why that could be?

 

[andrew_wright]

Hey guys, did a compression test on the S3, results:
Cylinder 1 195
Cylinder 2 155
Cylinder 3 190
Cylinder 4 195

Obviously there's an issue with Cylinder 2.
While performing the test on Cylinder 2 there was a loud pop noise, this did not occur on other cylinders. Any idea why that could be?

Rings or valve seals most likely

Sent from my Nexus 6 using Tapatalk

 

[scotty_24]

Seems localised to one cylinder.
Stem seals, guides, worn rings, cracked cylinder head (thats what was up with mine), piston damage (extreme but possible, ive helped change an engine that has a partially melted piston causing low compression)

Only way to find out is to whip the head off and start investigating.

If you have access to / have someone local a cylinder leakage test may point you in the right direction before tearing the head off.

Elring do a full head gasket set including stem seals for approx £80 at euro. Then you just need head bolts which work out £20-30 at the dealers / euro.
Millions of standard pistons lying about if needed, Valve easily sourced too.

Parts wise the cost isnt much. Its just the ball ache of investigating.

Just depends on how far you want to go with it

 

[Stuart B]

chuck some oil down the spark plug hole and retest?

 

[badger5]

Seems localised to one cylinder.
Stem seals, guides, worn rings, cracked cylinder head (thats what was up with mine), piston damage (extreme but possible, ive helped change an engine that has a partially melted piston causing low compression)

Only way to find out is to whip the head off and start investigating.

If you have access to / have someone local a cylinder leakage test may point you in the right direction before tearing the head off.

Elring do a full head gasket set including stem seals for approx £80 at euro. Then you just need head bolts which work out £20-30 at the dealers / euro.
Millions of standard pistons lying about if needed, Valve easily sourced too.

Parts wise the cost isnt much. Its just the ball ache of investigating.

Just depends on how far you want to go with it

thing is, whatevers leaking inside, is inside..
head off is inevitable to fix/find

cyl leak down may show where, but the inevitable is head off

 

[SteveSAS]

Rings or valve seals most likely

Sent from my Nexus 6 using Tapatalk

I was lead to believe that a compression test wouldn't show valve stem oil seals just piston rings, or am I wrong?

 

[superkarl]

I was lead to believe that a compression test wouldn't show valve stem oil seals just piston rings, or am I wrong?

By valve seals he means the valve sealing to the seat in the head. Not the stem seals.
Stem seals might show as smoky start up as oil leaks through and down the guides when stood and cold. They go quite brittle with age