Help diagnosing 5.3 noise

[1badc4]

I have made other post about my recent purchase of a 2001 Tahoe with supposedly spun bearing to drop my 5.3 with 183K out of my rusty Suburban in. the Tahoe motor doesn't really act like a spun bearing. great oil pressure and runs smooth, just has horrible knocking. tons of you tube videos of trucks with same issue. some cleaned with motor flush some had severely pitted lifter which also wiped the cam. I at the point do I just do swap or try to just fix this one? the noisy Tahoe engine has 158K miles on it. I first need to determine the problem with it. I have tries seafoam with no change, then I pulled valve covers and nothing is obvious there. next step pull the heads. does anyone have a good idea what the noise is. I am not familiar with the LS platform and find it remarkable that a pitted lifter can make so much noise. thanks for looking.

 

[Larryjb]

If you are already prepared to swap the motor, send in an oil sample, pull the heads and consider having them rebuilt. If the oil analysis shows relatively normal wear on everything else, it could be worth it.

While it's not in my interest, other take the opportunely to put a different cam in.

 

[swathdiver]

...does anyone have a good idea what the noise is.

No, but I suggest getting a mechanic's sthethoscope or a long extension/breaker bar and stick one end to your ear and move the other around the motor and accessories until you nail it down.

 

[iamdub]

It sounds too "fast" at idle to be a lifter, like twice as fast. This leads me to suspect something in the reciprocating assembly that would tap/knock in both directions, such as a wrist pin. But a really bad rod bearing could do the same. Of course, two equally-FUBAR'ed lifters (one intake and one exhaust) would sound twice as fast as a single lifter. But that sounds bigger than a lifter.

 

[Doubeleive]

sounds like rod knock to me, it's just a matter of time now I wouldn't take it out of town

 

[jeffsyukon]

Did you try running it without the accessory belt installed. Just to make sure its the engine.

Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[mountie]

I've heard that kind of noise before ( sort of, too high of a pitch for a rod / too fast & too low of a sound for a rocker)....... On my 5.7. GMC truck..... Forward pump in my transmission made the exact sound.
What is the sound level below, underneath, at the driver's door ( transmission), compared to above, over the engine??

( No codes??)

Also, sound level below, at front of engine area ( rod) ??

Compression test ( valve train?)

A loud sound can echo all over the place.

But as Swathdiver suggested, get a stethoscope !!

 

[1badc4]

Thanks for all the input, I did get a stethoscope, really found nothing definitive. I pulled bell housing inspection covers. I could see pretty much all the flex plate and was able to verify all the TC bolts were tight. looks like brand new torque converter. also drained oil and zero signs of metal. I pulled valve covers, learned nothing, pulled rocker arms and found 6 of the 8 push rods on the side I took apart were what looked like ground down(see pic) I was only able to pull 6 lifters so far and ran out of time. the 6 at first glanced looked okay. really odd? haven't touched it in a few days. trying to finish the stereo install on my Corvette which has the dash and interior ripped apart. I have decided to just yank this 5.3 and drop the one from my Suburban in and just be done with it. interesting comment on trans pump noise but after looking at the push rods I assume that is the culprit.

 

[1badc4]

If you are already prepared to swap the motor, send in an oil sample, pull the heads and consider having them rebuilt. If the oil analysis shows relatively normal wear on everything else, it could be worth it.

While it's not in my interest, other take the opportunely to put a different cam in.

No interest in performance cam. my C4 is for fun. this will be my daily

 

[-DIRTBAG-]

If it was a rod bearing there wouldn't be that kind of oil pressure. I've blown up my share of engines and I speak from experience. LOL

In my opinion, that engine is worth tearing down further to examine! Sounds more top end, but I'm def no expert.