Serious help needed

[MyM3isKillingMe]

So looong story short. Changed the head gasket on my 04 M3 due to misfiring and compression test failure. Head checked, cleaned and reinstalled. Vanos updated and valve adjustment done. Now the car hasn’t been right since. It’ll start and idle but will not drive. It has great compression when it’s cold but when it reaches operating temps it fails compression and starts to misfire incredibly bad. I need help! I’m either gonna sell it for parts, or pull the engine and rebuild, but I’m kinda hoping for a path to head in if I rebuild. Also, due to work and waiting for parts to come in, the car sat from mid December to early February with the engine pulled apart.

[Slideways]

Are there any error codes and what parts were used during the head gasket replacement?

[sapote]

It has great compression when it’s cold but when it reaches operating temps it fails compression and starts to misfire incredibly bad.

Post the compression numbers for all cylinders for cold and hot engine condition.

Note: it's not recommended to remove spark plugs with a hot engine for fear of strip the threads.

[MyM3isKillingMe]

Slideways, the only error codes it is giving, and I don’t remember numbers off hand, are for misfires on all cylinders and then a general P1341. With the 1341 code all the possible causes for that one have been found and fixed.

Sapote, the shop it is at currently told me that when cold cylinders 1,2 and 3 are at 192 PSI and 4,5 and 6 are at 190. When it’s at operating temp all 6 read between 85 and 95. That’s the most I’ve gotten from the shop.

[Ramps]

Almost seems like the valve adjustment is way too snug and when the engine warms up the shims expand slightly and the valves can’t close all the way. That could explain why the compression drops significantly but not to zero. It’s a strange issue that’s for sure.

[sapote]

Sapote, the shop it is at currently told me that when cold cylinders 1,2 and 3 are at 192 PSI and 4,5 and 6 are at 190. When it’s at operating temp all 6 read between 85 and 95. That’s the most I’ve gotten from the shop.

Ask the shop to measure the valve clearance with hot engine if possible; if not then with cold engine.

[D-O]

Almost seems like the valve adjustment is way too snug and when the engine warms up the shims expand slightly and the valves can’t close all the way. That could explain why the compression drops significantly but not to zero. It’s a strange issue that’s for sure.

First thing I would check.

[MyM3isKillingMe]

Sorry for the delayed responses; I've been busy with work. So I called the shop, and he did make a valve adjustment. I had done one while putting the head back together, and the mechanic said there were three that I had done too tight. He fixed that, which momentarily helped, but the compression loss remained. I don't know anymore. I'm leaning towards maybe the shop that inspected the head did a piss poor job, or there is some significant issue with the block.

[Icecream]

How did the head gasket look when you removed it?

[sapote]

I just can't think of what else can cause the major leaking when engine is hot beside valves are not completely closed. Even if the piston rings with little ring gap, it should be tighter and not leaking more.
Do the cylinders have new cross-hatch hone lines? Maybe the hone lines are so deep that it cause leaking via the rings with hot thin oil.

[MyM3isKillingMe]

How did the head gasket look when you removed it?

The head gasket was in bad shape. It was broken between 1 and 2, 2 and 3. It was fine between 3/4 and 4/5 then broken again between 5/6. There was minimal pitting between cylinders 5/6 that was eliminated when the head was shaved. Everything else was in pretty good shape.

[MyM3isKillingMe]

I just can't think of what else can cause the major leaking when engine is hot beside valves are not completely closed. Even if the piston rings with little ring gap, it should be tighter and not leaking more.
Do the cylinders have new cross-hatch hone lines? Maybe the hone lines are so deep that it cause leaking via the rings with hot thin oil.

Honestly, I don’t remember what the hone lines looked like. I didn’t mess with anything there other than sticking rags in there to keep moisture out. I almost wonder if my piston rings didn’t seize up just sitting there so long. I know that would be a rare case, but nothing with this car has been normal.

[Icecream]

The head gasket was in bad shape. It was broken between 1 and 2, 2 and 3. It was fine between 3/4 and 4/5 then broken again between 5/6. There was minimal pitting between cylinders 5/6 that was eliminated when the head was shaved. Everything else was in pretty good shape.

What gasket did you use to replace it? Was the block ok?

[bigjae46]

What are the compression numbers?

I think 90% of all machine shops suck.

[sapote]

The head gasket was in bad shape. It was broken between 1 and 2, 2 and 3. It was fine between 3/4 and 4/5 then broken again between 5/6. There was minimal pitting between cylinders 5/6 that was eliminated when the head was shaved. Everything else was in pretty good shape.

Stainless steel gasket that hot gas ate through in 3 places sounds concerning. Assuming the same issue happened with the new gasket, this should not cause the loss of such low compression as people with this kind of leaking between cylinders reported the detonation noise.