Thought I’d share what’s going on with my 2012 6.2L Yukon XL. Warning its long, but perhaps it will help someone with the same issues.
The short & sweet:
L94 6.2 AFM motor with cold start noise. Lifters were replaced prior to our purchase about 9 months ago, and this week my dealer replaced the camshaft & lifters noted camshaft damage. Videos of noise before and after below. There is still a noise after the repair, piston slap - and would you say normal?
The detailed story.
Purchased 9 months ago in North Alabama. 2012 Yukon XL Denali 6.2L (L94 with AFM) AWD. 1 Owner, 89,897 miles. Apparently at 89,741 (2 months prior to purchase) the lifters were replaced under powertrain warranty, no evidence the camshaft was replaced at that time.
I purchased it without that information provided. But no problem, it was running smooth at the time, warm spring Alabama temps. My dad works in parts so had a friend pull the RPO codes & transaction history for the truck, thats how I found out about the lifter work.
I did a clean up oil change right after purchase then swapped to my AMSOIL batch on hand.
Fast forward to November 2015 timeframe. The nights are getting cooler, and I start to notice the noise at cold starts. The noise disappears once the motor warmed up, and I mean FULLY warmed up. It would clatter for 15 miles to town. I started researching and found TSB & lots of reports of lifter noise, piston slap common with these motors. I honestly wasn’t sure which it was so I laid out my plan to try and eliminate the lifter noise possibility since it was just repaired.
From the start of November I completed 3 oil/filter changes. I downgraded from my AMSOIL filters and oil to ACDELCO filters and whatever Dexos oil I could get my hands on. I removed the intake manifold and did a good cleaning of the manifold and intake valves (added a nice catch can as well). I replaced the oil pressure sending unit and the little filter (it was clean but had to check). I removed the valve covers and removed each rocker, cleaned each pushrod with a pushrod brush & B12. I then sprayed a little B12 through each pushrod onto the lifters. Then poured fresh oil over the rockers to prevent dry start. All looked good internally from the get go.
After the cleaning & immediate oil change the first start up sounded good! I honestly thought some contaminates just got in the lifters and the cleaning helped. In hindsight the temp was around 60 so the sound was probably just muted. The next day a cold morning, the noise was back. Now even more of a shrill at times with any acceleration. The holidays hit and delayed my trip to the dealer.
So last Tuesday I dropped it off at the dealer with 97100 miles. I simply told the service lady it had a bad cold start noise with a prior history of motor work before our purchase & to please have it left outside overnight for a cold am start. The next day she called to say the mechanic has ordered a camshaft & is trying to find out from the previous dealer if the camshaft was ever replaced. Would take a week to repair under powertrain. I had him replace the oil pump & water pump while he was doing the surgery at no extra labor cost.
Picked the truck up last night. The mechanic stated he could not find any evidence that the prior dealer replaced the camshaft only the lifters at 89,741. So he replaced both the camshaft & all lifters again. Stated he did find camshaft damage & not sure if it occurred before my purchase or not since it wasn't replaced. He said the motor internally looked real good for one of this millage & the pistons were rather clean (he speculated they had carbon knocked off during its last tear down).
So now, the next morning, the temp is 30 outside. I start it up and it has a similar noise
to what I brought it in for. It still continues to tap for a good 15 min of driving.
Piston slap? I'm hoping this is just the normal noise & we can go on for another 10 years with no major tear downs. Please set my mind at ease. Thanks!
10-4 thanks for the responses!