04 Silverado started knocking, what could it be? Rebuild started

[ivin74]

The truck is my son's 2004 silverado extended cab. He has it cam'ed out, headers, tune and other misc stuff including a high perf transmission. The truck is not his daily. This afternoon he took it for a drive and got on it hard. After a couple of runs he heard some knocking. I would like to hear from the experience folks what you all think broke.

He is going to get it towed to my house tomorrow, probably will start by removing the heads and inspect the top end.

 

[rockola1971]

If that aint an exhaust leak then its definitely a rod knocking. OUCH!

 

[Snowbound]

Hard to tell from video. Could be a bearing, did oil pressure fall off? Could be in the valve train. First thing is to find out if the noise is high or low. Almost sounds like collapsed lifter I had a few years back.

 

[Donal]

The truck is my son's 2004 silverado extended cab. He has it cam'ed out, headers, tune and other misc stuff including a high perf transmission. The truck is not his daily. This afternoon he took it for a drive and got on it hard. After a couple of runs he heard some knocking. I would like to hear from the experience folks what you all think broke.

He is going to get it towed to my house tomorrow, probably will start by removing the heads and inspect the top end.

Remove spark plugs, take compression reading and record for all cylinders. That will identyfy the cylinder with a problem. Remove valve cover for the bad cylinder and check valve train. Repair as needed.
Sounds like a exhaust valve is not opening.

 

[THarber]

Sounds like valve train to me. Pull valve covers first and I bet you'll find a tossed rocker arm and possible bent push rod.

 

[MassHoe04]

Fingers crossed it is something easy (and relatively cheap) in the head like rocker or push rod...
Hoping for the best possible outcome for you!

 

[OR VietVet]

I am with everyone on this. Is the normal oil pressure still there? I doubt it. Sounds like also has an exhaust leak at the manifold but may not with all that noise. Remove covers and get a look see and whatever you do, fix it right and don't band aid it.

Please report back here about what you find out. Compression test as well before removing cover(s). Make sure all plugs are out and remove fuel injection relay when you do the compression test.

One last thing: There is a low down knock noise that I feel sounds like a rod knock as well as the upper end tick noises. So, like @rockola1971 said, I would have that in the back of my mind when diagnosing this.

 

[ivin74]

My first impression was a bent push rod, still waiting for my son to get it tow to my house to give it a proper diagnosis.

Hard to tell from video. Could be a bearing, did oil pressure fall off? Could be in the valve train. First thing is to find out if the noise is high or low. Almost sounds like collapsed lifter I had a few years back.

You are right it sounds like a collapsed lifter but this truck does not have the AFM system.

 

[Snowbound]

First thing I would do is check oil for any glitter on stick. Assuming it hasn’t gotten any worse, start it up and see if you can pin point if the noise is high or low or what side it’s coming from and see what oil pressure is. If it’s higher up on engine, pull valve cover or covers and look for play in rockers. It could be a bad lifter roller and/or cam lobe. They are more prone to flaking cam lobes than they are spitting a bearing.

 

[rockola1971]

The problem with theories of the sound being a collapsed lifter is if you listen closely to the knocking you will hear a slap after the knock. It isnt every time but it is a prominent sound. That knock slap routine ive only ever heard from a rod knocking.

"This afternoon he took it for a drive and got on it hard."
I take this to mean he was getting hard in the throttle and revving it. Which is when a rod bearing will decide to spin.