Anyone familiar with engine knock noise from faulty DOD?

[16K2XX]

Hello,  noob user here.  I am in the process of buying a 2016 Silverado 1500 with the 5.3 L83 AFM/DOD engine.  During the test drive I noticed a knocking sound, what almost sounded like an intermittent rod knock under light loads. My guess was a sketchy front CV axle joint making a noise, and assumed the intermittence was from moving the steering wheel.  But the service manager at the dealer drove it and said the noise is coming from the engine, and is a faulty lifter (tied to the DOD feature) causing the knock only on deceleration. Or when it goes into V4 mode the knocking noise is brief and barely audible, but I definitely hear it.  Not the kind of noises I want to hear on any rig!

My question: Has anyone ever heard of the DOD lifters causing a knocking (similar to a rod knock, but slower speed/tempo, so valve-train would make sense) noise at random times?  I have searched all over the innerwebs, and they all mention a tick, collapsed lifters and misfire symptoms, but never a knocking noise on decel.   I ask, as I don't know how much faith to put into the Chevy dealer (I never buy rigs from the dealer) to really know what the issue is.  We have the sale in process, but not taking delivery until the issue is resolved.  They are taking the engine apart to assess what is wrong, and they are on the hook for all of the repair costs, and even threw in a 2 year service contract.  Just curious if this is a common problem, or possibly misdiagnosed.  I love the truck, but I can't in good faith blow $30K on a truck with knocking noises!  - Thanks in advance. 

[newdude]

Yes they can make noise.  Tick, knock, etc.  The vacuum pumps can sound similar if they fail too.  It could be a lifter eating the cam too.  

[16K2XX]

5 minutes ago, newdude said:

 It could be a lifter eating the cam too.   

Thanks. That's kind of what I expect, going from the noise, and what they told me. Sounds like more than a stuck lifter noise or typical valvetrain noises from bad lifters. Crossing my fingers! Only has 89K miles on it.

[Lsgun1]

Don't buy it. Find another truck. It's probably why someone else traded it in.

Edited September 4, 2020 by Lsgun1

[Donstar]

Welcome to this forum and good luck with this purchase.   It sounds like you are buying this truck from a dealer even though you make a point of saying that you never buy from a dealer.  I appreciate that you may get better deals privately but, like in this case, dealers will often offer some type of warranty.  Peace of mind has a value!   My last truck with the 5.3 had to have the engine taken apart by my dealer at around 50k miles.  It gave me a subsequent 100k miles trouble free miles.  Enjoy your new truck!

[diyer2]

I don't understand why you don't find another truck. I would walk away no matter how they sweetened the deal. 

[flyingfool]

check the KR  on an obd2 scan tool

[16K2XX]

8 hours ago, diyer2 said:

I don't understand why you don't find another truck. I would walk away no matter how they sweetened the deal. 

 

Thanks for the responses!

We have, driven about a dozen or so, however we have found for a truck in the same cosmetic condition/features we like is consistently $4-5K more than this 2016.  Aside from the engine issue the truck is MINT, sat in a garage for four years, then was traded in.   Yes it's a messy situation, I may be a glutton in some ways as I almost always buy my rigs in some broken state (head gasket, blown tranny, broken timing belt/chain, etc.) and fix them myself for a fraction of the cost of buying one off a dealer lot.  However, in living debt free for decades now:  need to build credit, so this is the first rig on the purchase block in decades that I won't be on the hook to repair myself. Not many private party sales, or broken 2014-2019 Silverado's,  but fate somehow brought me to this one lol     - We can back out anytime, we made that clear, but at this point I am just curious what it is, and if it will need a reman engine or not.   Worse case, the cam is damaged, or a lifter is sized in the block requiring a GM rebuilt engine with a warranty,  I am ok with that, given the $5K discount. We would in no way buy it and drive off with engine knock!  It just slipped through the cracks, and must be why it was traded in.  Whether we close the deal or not, it is an interesting study of the L83 platform for me.  I am new to the LS/LT scene, but I have been a die hard Chevy guy for 40 years, so it's more of a learning journey for me at this point.  Plus I LOVE the look of the 2014+ Silverado's - as a 20 year Square Body owner.  Feel free to try and scare me away though.   

To me the engine is a moot point almost, as I already want to drop an LT4/5 in it and let her EAT. lol

 

 

[flyingfool]

you can get a used 6.2 motor from a yard for about $2500 with low milage.. while the used 5.3 motors are even cheaper..  pull and overhaul the stock unit after a swap. keep for back up.

 

i might suggest you visit  https://www.hemmings.com/ 

 i found some nice trucks with low miles, elderly owned  from model years 2000-05 they're all garaged kept

Edited September 5, 2020 by flyingfool

[flyingfool]

from AC delco youtube, the tick noise is a collapsed AFM lifter

 

[16K2XX]

We never noticed a valvetrain tick, just a knocking/thunking noise. But the AFM/DOD is suspect last I heard.

[16K2XX]

Update on this one:  The AFM lifters were bad, (on both sides) so they were replaced (cam was OK), and they are waiting on a fuel rail line that cracked going back together.

Found a video that audibly demonstrates the exact noise we discovered for anyone curious what they sounded like.

 

[16K2XX]

The dealer finally got it all back together, took delivery, needed new lifters on the driver side.  Runs great now! Now time for a long road trip!