[Oscarvan]

Wife's Denali with 126,000 miles. Called me today that it was making a bad noise.... Drove to meet here with the trailer and carried it home.

Sounds like the piston slap has suddenly gotten REALLY bad........

Suggestions? Will a compression check show anything if this is the case?

Thanks.

 

[silverado002]

Piston slap is usually a short period knock right after cold engine start up. A few minutes usually. If you have a knocking noise after engine warm up then you need to check your oil level. What is your oil pressure? Use a mechanics stethoscope to localize the knock.

 

[Oscarvan]

Oil level and pressure OK.

 

[xPosTech]

Piston slap or rod knock? Drain the oil and filter. Cut the filter open and look for metal flake in it and the oil. Post the results.

Ted

 

[Oscarvan]

After starting it fresh this morning it appears to be in the top end, which could be good news. Took it to an independent repair shop right down the road here that's been doing work for me for years. Don't have the time to get in to it myself.

 

[RayVoy]

Hmmm, top end and a 2012, if it's an AFM motor it might be cam and lifter failure.

 

[Oscarvan]

OK.... change of plan. Dude doesn't have time till next week..... Soooo, brought it into my shop. Got the valve cover off, and I have one rocker arm that's flopping all over the place..... Probably 1/8" of play, hard to measure.

Now what.......?

 

[RayVoy]

What cylinder?

Number one is front left (from driver's seat)

 

[Oscarvan]

#4 intake. Rotated engine through, valve not moving very much.

Pulled rocker and push rod. Rod is good. Stuck a scope in there. Hard to tell but the lifter looks boogered up. In the process of pulling the intake manifold. Hope to get to the lifters without pulling the head.... But a lot of Chevy motors require you to pull the head.

Of course it's also possible that the Cam is messed up.

 

[RayVoy]

1, 4, 6 and 7 are the AFM lifters

You need to do some research, lots of info on the site, most is not good news, sorry

 

[Oscarvan]

Thanks for all your input Ray....

Intake manifold is off. No lifters to be seen. Head needs to come off. Three Exhaust manifold to down pipe nuts VERY uncooperative. PB blaster on the case overnight.

Read up on AFM. Yes, special lifters. Some extra things to watch but still sounds doable.....

 

[Flyinfool]

If it is AFM, I would seriously look into deleting the AFM altogether since you will be replacing most of the parts anyhow. A repair will still fail again. An AFM delete is good forever.

AND

Since you are putting in a new cam for the AFM delete, you can always get one with slightly bigger bumps.......................

 

[Oscarvan]

Yeah, thought about it...... Since this is the wife's day to day mobile I don't think we need (even) more ponies. I think I am going to put new AFM lifter in that side, and this spring trade it in on something that runs on all 8 all the time.

 

[RayVoy]

If you read about the AFM problems on this site, your probably aware that lots of times a failed AFM lifter may also damage the cam lobe

 

[Oscarvan]

If you read about the AFM problems on this site, your probably aware that lots of times a failed AFM lifter may also damage the cam lobe

Yeah, I read that. If that's the case we are definitely deleting the whole crap show. I finally "re-educated" the hardware on the exhaust side of it and have the exhaust manifold off. It's down to pulling the head. No time tomorrow, Saturday morning we'll know a lot more.

 

[Oscarvan]

BTW I appreciate everyone's input and moral support.

 

[RayVoy]

Yeah, I read that. If that's the case we are definitely deleting the whole crap show. I finally "re-educated" the hardware on the exhaust side of it and have the exhaust manifold off. It's down to pulling the head. No time tomorrow, Saturday morning we'll know a lot more.

I haven't had an LS apart; but I'm wondering, do you need to remove the head to pull a lifter?
I thought intake and valley pan and you have access to lifters. I thought they were pulled in groups of 4 lifters

 

[Oscarvan]

 

[Oscarvan]

The tubes you are looking at in the valley are the oil channels that command the AFM lifters into on/off mode. The lid on the valley has oil channels in it and the solenoids that control the oil down the channels.

 

[Oscarvan]

Well, I think I can stop taking stuff off. Got down to the lifters and the keen eye will quickly see the problem. It appears the failure was contained and that the cam is unscathed. I don't feel like tearing down the other side of the engine and everything in front of it to get the cam out, so the delete kit is out. I'm putting 4 new Mickey Mouse lifters in and putting it back together. With a little luck we'll get enough miles out of the left ones to last us 'till the next truck.......