Head gasket issue?

[tom slick]

As part of a 200k mile check-up on my Protege5 I completed a leakdown test. Leakdown in all four cylinders was acceptable, less than 20%, but on 3 of the cylinders I could hear air leaking into the adjacent cylinder. I did not hear leakage into the intake or exhaust. Adding a little oil to the cylinder brought the leak down up into the 5-10% range. There were no bubbles into the coolant and the car has not been using coolant or oil. I've done several of these tests before but I've never heard air leaking into an adjacent cylinder. Is it time to pull the head and check it out?

 

[Drew99GT]

Are you sure you weren't hearing air going into the crankcase and head area past the rings? The drain back holes on top of the head might be located by those 3 cylinders. Any pressure coming out the oil fill hole or PCV hoses? If it's still running good, there's no coolant consumption, and the spark plugs look good and even across the cylinders, I'd just keep and eye on it.

 

[tom slick]

It runs good. The sound was coming from the spark plug hole, covering the hole made the sound disappear. I'm going to investigate more today.

 

[Bluestream]

Have you done a compression test?

 

[mechtech2]

Considering your good #s: If air really was leaking into the adjacent cyls, it probably is valve leakage into the next cyl. Either intake or exhaust. [Manifolds are shared]

 

[229]

If you had the valves closed on the adjacent cylinders and heard air coming out of the sparkplug holes then I would be concerned about cross cylinder leakage by the headgasket. If this engine is difficult to relieve the valvespring tension on then I would replace the other three sparkplugs and listen at the other areas that can escape air in order to diagnose.

 

[Chris142]

2 intake valves are open at the same time

 

[tom slick]

I checked it again today. The leakage sound is not coming from the intake, exhaust, or PCV. The sound definitely goes away when you cover the spark plug hole of an adjacent cylinder. #3 cylinder has 30% leakage the others are 15% Testing #4 cylinder I get sound from #3. Testing #3 I get sound mostly from #4 but some from #2. Testing #2 I get sound from #3. Compression test results: #1 165 psi #2 165 psi #3 150 psi 10% difference #4 165 psi. Seems like #3 is leaking.

 

[mechtech2]

In addition to my other post, air past the rings will go into the crankcase, and up the other cyls. So we are still not sure yet if a head or gasket is bad.

 

[mechanicx]

It does look like the headgasket is slightly leaking. It's probably the headgasket just nearing the end of it service life. Being somewhat lazy and a tightwad I'd consider putting it off until it shows more signs of being a real problem.