2001 Chevrolet Tahoe 5.3 Engine knock - help to identify

[kjetilaf]

Hi

i have an 01 Tahoe 5.3 that got a heavy knocking sound after sitting for approx 14 days.
What happened is a failed start attempt at first, it turned over and instead of starting it just made some noise and did not start,
restarted it and then there was a new knocking sound.
I suspected lifter that needed to be filled with oil, but the sound did not go away after idleing and reving it a little.

What i have done
I have dismantled the top covers on each side, and inspected valvesprings, rocker arms. I cant find anything out of the ordinary here..

I would really appreciate someone with the same type of knock ''frequency'', that have found root cause.
I suspect lifter or bent rod, but dont understand how that would develop so quick.

If its lifter, should i not feel play when checking the rocker arms?

 

[strutaeng]

That to me sounds rather like rod knock. A lifter tick is a cycle half of the engine RPM, and sounds similar like a diesel.

Have you drained the oil for inspection? Look for a glittery sheen on the oils drain pan. Also, remove the oil filter and cut it open to inspect the filter media.

 

[kjetilaf]

That to me sounds rather like rod knock. A lifter tick is a cycle half of the engine RPM, and sounds similar like a diesel.

Have you drained the oil for inspection? Look for a glittery sheen on the oils drain pan. Also, remove the oil filter and cut it open to inspect the filter media.

it is on my todo list,
so far i have done a compression test with all plugs out,
and one in the suspected area is reading lower. / 131 psi / 9 bar
the rest were reading 174 psi / 12 bars

with camera there is also signs of some scratches on cylinder wall, that can explain the lower compression, but does not explain the sound.


i am also heading for a bottom end / rod bearing issue here... maybe i should just drop the pan before deciding what to do next...

 

[rockola1971]

Holy Smokes! If that isnt a rod knocking then its a cracked flywheel. That does not sound good at all.

 

[Mudsport96]

Could be a cracked flywheel like Rockola said. In your first post you said it made a noise when trying to start it. What kind of noise?
Could be a rod knock.
What caught my eye was the HORIZONTAL mark in the cylinder.

That looks like the mark a ring makes when an overheating engine is shut off and rings seize until the engine cools. Have you ever overheated it?