Unknown Lifter Knock

[RockGlock86]

So I have a 2007 Yukon SLT with 5.3 LMG AFM motor, currently at 155k. Last november had it in the shop and they pulled the driver side head and replaced intake and exhaust lifter on No1 as the AFM lifter had separated and the spring portion was kinda falling off. So afterwards it runs great and back on the road. About June this year starts having the same issues and symptoms but now its Cyl 5 misfire, not an AFM Cyl. Figure its time to delete AFM anyways if I am doing further work.

So I used a Northern Auto parts AFM delete kit without cam, Summit 8718 Cam and 3 bolt timing gear and ARP bolts, Black Bear ECM/TCM. Reassemble engine and fires up no problem and runs fine for 5 minutes or so and starts a tick which transitions to a loud knocking sounds over the next 5 minutes. Coming from the driver side bank, around No 5. Not sure if it is 5 though, might be 3, I cant isolate the exact location of the noise.

Turn engine off pull valve covers and inspect drive train and everything looks fine. I only installed new lifters, used same push rods and rockers. Run engine with cover off and everything looks as it should. all push rods are tight, rocker arms are not bent or loose, valves are all tight and opening and closing as they should. Now noise it down to a slight tick like my 2000 6.0 2500, so i figure its fine. take it for a test drive and the sound comes and goes several times, in and out from a ever so slight standard tick to a hammer sound back to a tick. On initial startup it ticks while it pumps up pressure for maybe 5-10 seconds, probably need a new oil pump or O-ring in the pickup tube. Then the it makes no noise initially, as engine warms up the tick shows up and it most prevalent when engine is hot. Oil pressure on initial start up is <5psi for 5~ seconds then goes to about 35 psi. Under acceleration at over 2k rpm it will raise to 40-45psi.

I have done everything I can think of to quiet a noisy lifter short of removing the head and changing the brand new lifters on the driver side. Pulled the rockers back off and sprayed chemtool down the pushrods, fired it up and it sounded super quiet and smooth and that lasted about 3 miles then back to tick/knock. Changed the oil and used liquimoly MOS2, lasted about 5 minutes of idling and went back to tick/knock. Seafoamed the upper engine through the brake booster hose, sounded good for about 5 minutes of idle and then tick/knock.

No codes, misfires, hiccups, runs and drives great actually the only issue is it makes a loud knocking noise intermittently. I feel like if I had a louder exhaust I wouldn't even notice it.

I have owned loud diesel trucks and know that those engines are very noisy and sound like a typwriter. I have read that there are TSB's about Chevy engine noise. this seems louder than usual, and louder than the truck ever was before. but now that its deleted I'm not sure what its supposed to sound like.

So I guess my questions are,
Is it possible to have just installed a crap lifter?
Is it possible that Cyl 5 has some issue that sounds identical to lifter knock.
What else other than lifters could cause this issue?
Is it something else entirely and has nothing to do with lifters?
Whats the best way to diagnose the problem?

Thanks for your time guys.

Justin

 

[iamdub]

Have you ruled out a broken exhaust manifold bolt and/or failed exhaust manifold gasket?

Based on your story line, my guess is a piece of debris released during the operation found its way into a lifter and is intermittently plugging it up or it's a bad lifter. Lets hope it's not a cracked guide letting the lifter rotate in the bore or a spun cam bearing. It sucks to do so, but you may be pulling the head soon. Any glitter in the oil?

 

[RockGlock86]

All exhaust bolts were replaced with fresh studs and nuts and new exhaust gaskets. New buckets with the lifters, and no glitter in the oil, clean and clear. I ran it 20 minutes, changed oil. 50 miles changed oil. 150 miles changed oil. I ran a zinc additive the first time, and locus heavy duty stabilizer the second change and liquimoly truck the third. I'm at the beach now, but I'm thinking when we get back inland just pulling the head and dropping in new soaked lifters, I'm thinking of mopping the lifter bores too with kero

 

[BG1988]

have you put a new plug? swapped ignition coils? swapped wires? that is the basic steps to try..

also the oil pick up tube might be plugged up (or screen) or oring fail that is the cause for low PSI on startup

 

[RockGlock86]

New plugs, swapped wires around, swapped coils around, tried all that. I do need to drop the diff and pan and I want to swap to a high flow standard pressure pump with new rings in the tube. I don't think its lack of pressure tho that's causing the knock.

 

[iamdub]

All exhaust bolts were replaced with fresh studs and nuts and new exhaust gaskets. New buckets with the lifters, and no glitter in the oil, clean and clear. I ran it 20 minutes, changed oil. 50 miles changed oil. 150 miles changed oil. I ran a zinc additive the first time, and locus heavy duty stabilizer the second change and liquimoly truck the third. I'm at the beach now, but I'm thinking when we get back inland just pulling the head and dropping in new soaked lifters, I'm thinking of mopping the lifter bores too with kero

Lol
You sound like me when I open up an engine. Yeah, it's really sounding like a failed lifter. Do you know if that Northern kit uses OEM lifters? At the price for the kit, I'd have to doubt that. Prices for OEM GM parts has skyrocketed. I know the lifters alone are now more than twice what I paid last year when I bought my AFM delete parts. So glad I started parts collecting back then!

Once you have the head off, thoroughly inspect the cam lobes. It may be worth it to remove the valley cover for better visibility on the other bank's lobes.

Hoping for the best and keep us updated!

 

[iamdub]

New plugs, swapped wires around, swapped coils around, tried all that. I do need to drop the diff and pan and I want to swap to a high flow standard pressure pump with new rings in the tube. I don't think its lack of pressure tho that's causing the knock.

Nah, your pressure is plenty high enough. It might could be a little better with a fresh pump and plugging the relief port in the manifold. But it's fine as-is.

I've heard of the built-in O-rings in the valley pan gasket leaking under higher pressures, so I tapped and plugged my AFM towers. I used the Melling HV pump that's supposed to be the stock replacement for an AFM engine. I removed the relief valve in the oil pan and plugged the port and ported the oil pump. Before, my pressure was upper 20s at the lowest to maybe 50ish at the highest, depending on temperature and RPM. Now, my pressures range from 37ish at hot idle to 80 at 6,000 RPM. Still on the original 200,000-mile shortblock, bearings and all.

 

[thompsoj22]

did the pushrods go back in there original positions, A little to coincidental to me, duplicate gripe just different cyl? jmo, but snake oil additives just fk things up! Flush that crap out with whatever oil you used prior to the delete. It is possible that the new lifters simply could not seal/endure the additives that they were force fed. If the #1 pushrod had a blockage and was installed in #5 that could do it. You sound like you know what your doing so no implied schooling here! im sure you inspected for straightness/ blockage prior to reinstallation. The oil pressure should rise quicker than described so you may be on to somthing there. but a quiet valve train for the first 5 min and then start tapping would allow enough time for snake oil to work it's magic and colapse a lifter, Has the oil pressure allways been a little slow to rise? if it were mine id dump the oil/filter and run 4 qt's of wallmart brand full syn 5/30 and one quart auto trans fluid. run it in the driveway and try to keep the noise to a tick and not hold a sustained hammer sound. fill the new filter with trans fluid prior to install and remainder of the qt into the eng prior to the fresh oil going in. it ran quiet for 5 min, i would not pull it apart yet, but i would be gentle with rpm. do the oil change with the eng allready at op temp.

 

[RockGlock86]

So just got back from vacation. The plan is to pull the driver side head, scrub everything down, soak new lifters and put it all back together. The additives, Lucas break in zinc the first run of 20 minutes. Summit recommended a break in oil or additive. Lucas heavy duty the second round of 50 miles I figured it would help and the stuff is thick. After 50 miles I was ready to change it and it made the oil almost stringy. For the third change I used the LiquiMoly as I use it in everything in my Audi track car and it works great. I don't think it made a noticeable difference at all. I think I am just going to run regular oil after I swap this head. I have run Shell Rotella Gas Truck for 30k miles now and I really like it. My oil consumption really went down once I switched to it. I will have some pictures and a follow up in a couple of days. Thanks for the responses guys.

 

[RockGlock86]

I pulled the driver side head today and replaced the cyl 5 and 7 lifters, the forward lifter for cyl 5 was definitely collapsed, and the rear cyl 5, and both the cyl 7 lifters seemed off so I tossed new ones in I have had soaking for a few days. The cyl 1 and 3 lifters were fine and tight, no wear or strange marks or anything, cleaned all the rods and rockers and the head itself and used all new felpro bolts and a new gaskets on everything. Looking down at the cam everything looked fine on that. Ran it down the road and back, maybe 10 miles and no hammering knocking sound at all, just the regular Chev chatter. So if you see the Northern Auto DOD delete kit for 350 bucks and think its a deal, it might not be.