2.0L Fsi Awa, Leak Down Test

[Paul Waterfall]

Hi, just did a leak down test with only a 5% drop, leaking from the oil filler cap, from what I`ve read

this is blow past gases which is acceptable.

My main question is how can this be with a low compression reading averaging 100 psi, surely the

leakage would be greater.

Can anyone explain these results, did the test several times.

Thanks.

Paul

 

[desertstorm]

Compression can leak through bad sealing on the intake / exhaust valves. Also if the head gasket has failed .If you do a compression test and then squirt a small amount of oil into the bore and redo the oil will help to make a temporary seal on the bore so if the reading improves then it's likely that's where the issue is.

 

[Paul Waterfall]

If compression leaks through bad sealing of valves at TDC wouldn't the leak down be a higher percentage than 5% that I`m getting.

 

[desertstorm]

How much pressure are you using for the leakdown test ?
Is the battery strong on the car ?.

 

[Paul Waterfall]

Compressor set to 100 psi, connected the leak down and calibrated to the set position locked the regulator then connected to the plug hole.

The test gauge read 20 to 30 psi and a 5% leakage, I even connected to air line direct to plug hole and got a slight loss through the oil filler

as you would even at a 100 psi.

 

[Paul Waterfall]

The compression test was done hot / cold with and without a squirt of oil and WOT, the hot result was a couple of psi higher.

The leak down was done hot / cold and no different with the readings.