200K and counting

[SRQYukon]

If a lifter is collapsing I would expect possible misfires on that cylinder, even though you're not feeling them. Maybe monitor the misfires to see.

I know, it's a little puzzling. I would have expected a misfire, too. But I guess the cylinder still fires and maybe the valve is opening enough to partially fill the cylinder with fuel/air.

I watched some mechanic on YouTube repairing an NNBS with VVT DOD and he showed how roller lifters can separate and then spin around in the lifter bore. If something like that were happening, the roller would be misaligned with the cam lobe part of the time. That would cause lifter noise. So maybe something like that is happening. As suggested, changing the lifters might buy me another 50-80k miles. But, it may have also resulted in damage to the cam lobe, which means I'm done.

 

[iamdub]

I know, it's a little puzzling. I would have expected a misfire, too. But I guess the cylinder still fires and maybe the valve is opening enough to partially fill the cylinder with fuel/air.

I watched some mechanic on YouTube repairing an NNBS with VVT DOD and he showed how roller lifters can separate and then spin around in the lifter bore. If something like that were happening, the roller would be misaligned with the cam lobe part of the time. That would cause lifter noise. So maybe something like that is happening. As suggested, changing the lifters might buy me another 50-80k miles. But, it may have also resulted in damage to the cam lobe, which means I'm done.

Usually a ticking lifter is just from a small amount of slack and not a totally collapsed lifter. The engine will run fine and, like you said, just have less valve lift. You could send an oil sample to Blackstone. If the iron content is high, then you'll know you have some serious mechanical problems. If the lifter collapses so badly that it has a lot of slack, it'll usually be louder and that might be the intermittent knocking you're hearing. That could beat up the cam lobe and lifter roller. If the oil analysis shows mildly elevated iron, then it might be from the harder knocking. You could pop off the intake manifold and valley cover and, hopefully, the cam lobes of the cylinder(s) in question will be one of the visible ones. If it's/they're smooth, proceed with replacing the lifters.

If it just has a failed lifter that was just by chance and not due to abuse and/or lack of maintenance, then, I don't see why dropping in a new one (or all on that bank or both banks) wouldn't put it back on its track to 300K miles- where it should be.

 

[SRQYukon]

Thanks, Iamdub. I'm thinking I'll try that when a get some time. Thanks

 

[S33k3r]

I suggest changing the weight of your oil. From the described symptoms, maybe going to 0/30 could stop the start up tick. If the noise were happening during run time, I'd suggest a 10/40, for example.

 

[SRQYukon]

I suggest changing the weight of your oil. From the described symptoms, maybe going to 0/30 could stop the start up tick. If the noise were happening during run time, I'd suggest a 10/40, for example.

Worth a try. maybe.

 

[SRQYukon]

Update:
I took my Yukon to another shop and had them replace the pickup tube and o-ring. This completely solved my problem and I should be good for another 80-100K. Thanks all, for the advice. My son-in-law, who originally changed the o-ring and pan gasket was just being stubborn and insisting that this couldn't be the cause. When I took it back to have him pull the pan and check it, I actually thought that he had done that. Turns out he just ran some diagnostics on it and told me the valvetrain was shot (w/o pulling the pan and doing what I asked). If you could have heard it, you probably would have agreed with that diagnosis. I had to twist the arm of the rival shop to get them to do it. They also thought I was throwing away $500 on something that wouldn't correct the problem. I finally just insisted that they do what I asked. They were amazed that all of the valvetrain noise was gone. I've driven it a couple of hundred miles now and I believe it's quieter than it was before the issue came up. So apparently the inconsistent oil volume was the problem. I suppose that's where the factory gauge is lacking. It always showed 35-50 psi (except for a few seconds after start-up). But oil pressure gauges don't measure volume. But anyway, it gave me an excuse to buy the Duramax