V12TT

Background:
Car was shaking in idle. Indy shop replaced plugs, distributor and wires. It's still shaking after parts replacements and the shop pointed to no compression on V8 cylinder #4. All other cylinders read 140.
Took to another dealer for diagnostic and dealer said car needs a new engine.
Car runs fine and no CEL but shakes violently in idle. Coolant reservoir showed low fluid but no leaks were found. Muddy sludges were found at the oil filling cap. Oil drained and no metal dust were found.
Question:
Assuming passenger side head gasket is blowed. Can it caused no compression on 1 cylinder? Should it be low and not zero compression?
Multiple issues and not just coolant leaks?

kevinkpk

I'd look at pulling the head, might be a valve, or if you can look in the plug hole with an optic scope

V12TT

If I have suspicions that one ignition wire to the problem cylinder was disconnected and I removed the upper intake manifold and distributor already; would it be worthwhile to pull the head at this point?
What are the risks with pulling the head beside potential oil leaks from gasket replacements?

kevinkpk

Use a fiber optic scope to see if you have a burnt valve. You can pull the head, my suspecion is a valve at this point

V12TT

I will take this advice. Remove the spark plug and stick a camera into it. Great idea. Thanks

kevinkpk

If it's not making any compression at all, you'll see the issue if it is a valve, and I don't know where else to look with the problem you posted. I bought at Lowes a small fiber optic, gave it to my son, cannot remember what the name of it was.

V12TT

Will I be able to see a burnt valve? The spark plug is supposed to be new and removing it will allow me to confirm whether it has been fired or not. In hindsight, I should have looking into the plug first and not just depends on people words. Lesson learned.

kevinkpk

You should especially if you have "no" compression. Pull the pcv valve out with it running, there should be alot of blowby if it's rings.

V12TT

I pulled the spark plugs. No compression plug is on the right. Plug from good cylinder is on the left. Any thing obvious?

Closer looks at the plug from no compression cylinder:
Also I need to mention that I can remove the plug from the no compression cylinder with bare hand. It wasn't torqued down at all.

V12TT

Here are a few images from the zero compression cylinder. I don't know what I'm looking at. Please let me know if needing more images