Before replacing head or gasket, did you put any oil in the two leaky cylinders? I've read it's common to put a tsp of oil in the cylinder for the compression test but then +1 on the advice above.

Another tool I get to add to my box it seems. Hopefully I’ll run that down this week. Fingers crossed for a head gasket but there was almost nothing on 2 and 4, it sounded like how kicking over a bike with no rings left feels.

Regardless of head issues, is there any reason I should be concerned about the block? Seems the head is what sees the most extreme temps.

This has been an interesting exercise in troubleshooting. I’ve not had to do this on a 4-stroke engine before (let alone a car).

when you take the engine head off, you can use a flat-edge and feeler gauge to measure for block warpage and the maximum variance will be listed in the engine specifications. it usually doesn't happen as it's most often the head that warps.

If like you said, cylinders 2 and 4 have 30, you should have noticed the engine misfiring when you started the car. In your earlier post, I thought you said the engine ran smooth.

I would agree with the other post above, add a tea spoon of oil in cylinders 2 and 4 and check for compression again. I had noticed this in my 330i a few years ago where I did a compression test on a healthy engine and I remember cylinder 1 had 30 psi. I added a spoon of oil to all the cylinders and it helped.

I’ll check them again with some oil squirted in. The engine did seem to run smooth when I started it last week, no misfires.

You want to confirm not the rings brie you decide to do head job so hopefully you get some pressure even if not great. Changing out a valve or three not bad at all. I had to do 8/32 the last time I did a head overhaul. (broken timing chain whacked 1/3 of the valves)

Do you have an air compressor? Can you do a leak down test?

It's Dead, Jim ('01 3.0i)
 

I do have an air compressor but no leak down kit. It’s easy enough to retry the compression test with a squirt of oil in 2 and 4 that I’ll do that first.

Edit: I did try multiple runs on cylinders 2 and 4, so it shouldn’t be a gauge seating issue. Hard to believe that the rings could be so dry that they don’t seal worth a damn anymore but testing again is not a huge endeavor.

You can probably borrow a free leak-down tester from one of the auto part chains... it will likely tell you where the leak is... although if you are still low on compression after putting a little oil in cylinders, it won't matter much...the head has to come off.

I have seen only one instance where a piston or piston ring failure has caused the kind of compression loss you are seeing...It's almost always in the valves...or the head gasket..

Yep but def want to eliminate that possibilty since it's relatively easy


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