New noise

[JPaul]

So this morning I drove to work as always in the Alpha, and stopped at a Fastenal on the way to get some washers for the red H3. Well when I started the Alpha back up at Fastenal I started hearing a new noise. It's a grating kind of sound that is engine speed dependent. I did not hear it at all on the drive to Fastenal. Initially it was loudest at idle and would get quieter as engine speed increased, but on the drive home from work it started doing the opposite, it would be louder with higher engine speeds and at idle it was barely audible.

At first I was thinking maybe the starter wasn't fully disengaging and causing the noise, but after popping off the inspection cover in the bottom of the bell housing I did not see anything on the flexplate teeth that indicates they are rubbing on anything. I also used my mechanics stethescope to determine if the noise is internal to anything, but it was far quieter with the stethescope, I could really only hear it in free air. I'm worried it might be something in the transmission, but I have no idea since I have never dealt with a failing automatic transmission.

Thoughts?

[video=youtube_share;CkfrQrpjeEg]https://youtu.be/CkfrQrpjeEg[/video]

 

[JPaul]

Talked with a friend of mine and he's got me thinking it might be a cracked flexplate. I'm have my red H3 back together so I can drive that while I start tearing the Alpha apart. I'm going to start off with pulling the starter motor and see if that gives any insight/visibility into the matter. If I cant find anything that way, then the next step is probably going to be separating the transmission from the engine and digging deeper.

 

[JPaul]

Well, got the transmission pulled today. It really, really sucks doing that by yourself on the floor. If I could have even lifted the Alpha up enough to at least be able to sit under it the job would have been 10 times easier.

Flex-plate looks fine, transmission fluid looks ok, bit dark but nothing un-called for, no bad smell either. I spun the torque converter around as fast as I could to see if I could get it to make that same noise, or anything even close to it, but nothing out of the ordinary was emitted. It's possible that maybe it needs to be pressurized for it to make the noise? I still have no idea what that noise was coming from.

I'm going to pull the oil pan on Monday and see if there are any indications of abnormal engine wear. When I changed the oil a couple weeks ago there were a couple largish chips of steel clinging to the magnet on the drain plug, so that has me a bit concerned. Seeing how the engine has been running fine though, I'm not 100% sure they actually came from the engine internals, it's quite possible they got picked up some time before when the plug was out of the pan during an oil change or something. They didn't look like bearing material, nor really like they were chipped off from something like a tooth or anything like that. More like chips from metalwork. Really hoping I don't find anything wrong when I pull the pan, but we'll see.

If anyone can listen to the clip I posted initially and give me a better idea of what that noise could be I'd greatly appreciate it.

 

[mdocod]

Hi Jpaul,

The noise is occuring at a rate of about 1 time per 4-6 (estimated) engine revolutions.

Think about what on the car makes a complete revolution 1 time for each time the engine rotates about 4-6 times while the vehicle isn't moving.... Not a lot of options to choose from here and I'd be willing to be it is related to either a timing chain or serpentine belt.

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EDIT.... it just occurred to me... the 5.3L probably idles a lot lower than I was thinking. I'm thinking in terms of small engine idle speeds (~800RPM).. sure enough, looked it up and I guess the 5.3L idles as low as 500RPM... With that in mind, I'd be looking at valvetrain related possibilities.

https://www.youtube.com/watch?v=6aaI_e1z1E0

there's another 5.3L with a noise occurring at the same "rate." Sounds fairly similar. Put your stethoscope on the valve cover.

 

[JPaul]

That does seem to be at the same rate, and maybe it is lifter noise, but typically lifter noise is a definite tapping, whereas my sound is more like a metallic rubbing. I did change the oil the week before the noise started, but it seems odd that would cause the issue.

But you're right, I did the math and at 500 rpm that's just over 8 revolutions per second. With a 4 stroke that works out to about 2 cycles of a single valve per second which is about where this noise's frequency is at. So that sucks. Guess at this point I should just pull the engine and rebuild it, I have the transmission out already which is half the battle. I was planning on doing all this eventually anyway. But was hoping I'd get another year or so out of it before i needed to.

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[Guerrero]

Just my suggest.....remove the accesories serpentine belt, and start the truck for 1 or 2 minutes, and try to listen the noise....if the noise dissapear...you know where is pointing, if not, engine or transmission.

Be careful about the engine temperature, when you remove the serpentine belt, your water pump will be stopped. Put one person inside the driver seat looking the engine temp while you search the noise.

Hope its help!

 

[mdocod]

I wouldn't remove the whole engine.... yet... check around with the scope. That noise could be the tight hissing of a head gasket leak or exhaust manifold leak. Try to figure out the issue before pulling it. Think scientific method. You want to have a hypothesis about the noise, then PROVE that hypothesis before proceeding with a repair. Rebuilding the whole engine would probably fix it, but if it turns out to be something silly that can be fixed with the engine in place that will have been a waste. It's also a good idea to have it narrowed down before the rebuild so you can make better decisions about which hard parts to replace in there as it is being rebuilt..

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whereas my sound is more like a metallic rubbing.

Like a cam lobe scraping against a push rod?

Put the stethoscope down in the valley.

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I did change the oil the week before the noise started, but it seems odd that would cause the issue.

Just to double check... have you checked the oil sump? Made absolute sure there's oil in there? Suddenly developing engine noises after an oil change..... hmmm....

 

[JPaul]

I wouldn't remove the whole engine.... yet... check around with the scope. That noise could be the tight hissing of a head gasket leak or exhaust manifold leak. Try to figure out the issue before pulling it. Think scientific method. You want to have a hypothesis about the noise, then PROVE that hypothesis before proceeding with a repair. Rebuilding the whole engine would probably fix it, but if it turns out to be something silly that can be fixed with the engine in place that will have been a waste. It's also a good idea to have it narrowed down before the rebuild so you can make better decisions about which hard parts to replace in there as it is being rebuilt..

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Like a cam lobe scraping against a push rod?

Put the stethoscope down in the valley.

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Just to double check... have you checked the oil sump? Made absolute sure there's oil in there? Suddenly developing engine noises after an oil change..... hmmm....

Seems you missed where I said I already pulled the transmission, there is no starting the engine up to check for sounds now unless I want to tear my engine bay to shreds as the engine flails around on the motor mounts. It's got 160K on it, a rebuild isn't going to hurt it.

 

[mdocod]

Seems you missed where I said I already pulled the transmission, there is no starting the engine up to check for sounds now unless I want to tear my engine bay to shreds as the engine flails around on the motor mounts. It's got 160K on it, a rebuild isn't going to hurt it.

I'm under the impression an engine can be started/idled without a transmission behind it as long as the flywheel is on and the other engine mounts are attached.

Just don't rev the engine.

If it makes you feel better, use some bolts and blocks on the back of the engine to strap/support it better.

 

[Mr_Rich]

Possibly valve train related? It doesn't have that harsh sound of a little man with a hammer inside the engine. Some kind of peripheral noise is my guess...

 

[JPaul]

I suppose i could brace the engine with some jacks and wood blocks to make sure it doesn't tilt too far forward or back which is my main concern. Maybe I'll try that after work today.

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[JPaul]

Well, I put the starter back on and wedged a block of wood between the oil pan and crossmember to help keep it steady. Tried to start it and it wouldn't crank. I ended up pulling the parking/neutral sensor off the transmission and plugged it in and made sure it was in the park position, the engine started right up.

The noise is definitely from the engine, and more so it is a lifter causing it, i put my stethoscope on one of the valve cover bolts and I could hear the lifter tapping in sync with the grating sound.

Apparently the engine has had a lifter tick for a while, and unfortunately something in there decided to fail further. I'm hoping that at worst it will need a new camshaft and valve train. I really hope the block itself is ok as well as the crank and rods. If all those are messed up too then I'll probably just get a remanufactured engine. Since it's apparently the valve train though I'm hopeful that and metal particles from it were caught by the oil pickup screen and filter. We'll find out in the next week i think, looking it over it shouldn't be too bad a job to pull the engine out since the transmission is already out.

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[Reloader]

Drain the oil into a container and check for lifter roller needles. I've seen a few of these over the years with this problem. Stick a magnet on a wire into drain hole and see if anything sticks to it from on the floor of oil pan. Also check rocker as I believe they are roller rockers also.unfortunately when the roller lifter fails like this it can wipe out cam lobe. Oil pump is driven off crankshaft in timing cover. Changing camshaft not bad but to replace lifter you need to pull head. And if you do one you might as well do them all. And put in a nice performer cam. I believe PCM of NC has a cam and tuning package for this setup.
Another common cause of lifter tick on these 5.3s is poor oil pressure due to a leak at the pickup tube to timing housing. The o-ring seal fails and pump starts to suck air and cavitates. Anytime you drop the oil pan on these ingines always replace oil pickup tube seal. And oil pan gasket leaks are common too. You can't tighten bolts as the gasket is a metal gasket with a silicone bead on inside edge that compresses and fails with time.
This may seem like a lot of problems with this engine but there are so dam many of them out there that it can seem like they have issues.
Most engines are designed so that if low oil pressure exists, the valve train suffers first to protect the mains and rods.
Maybe you get lucky and have a bad roller rocker. We would just replace rocker and pushrod and fish out as many of the roller needles as we could from oil pan and top of head, new oil and filter and send them on their way. Any needles left would usually get stuck on drain plug magnet and get removed at next oil service. Also make sure lifter guide plate is bolted in place properly.
Wishing you good Luck.
If you have to replace engine with a reman unit be sure it's an aluminum block one as that's oe to save weight. Or have yours gone through by a reputable machine shop. That's how I would do mine.

 

[JPaul]

Thanks Reloader. When I changed the oil a few weeks ago the magnet on the drain plug had a couple 1/8" metal chips stuck to it along with some metal particulates, but nothing that looked like needle bearings. A friend of mine linked a video to me for an 08 Denali with the 6.2 with a bad lifter that was making the exact same noise as mine is, so it's definitely something along there.

I'm going to pull the engine and do a full rebuild on it rather than risk trying to patch it together just to have something else fail on me later. I'll keep an eye on the pickup tube. And I hear ya on the aluminum block, that's why I'm really hoping the block and bottom end are all ok so that I don't have to go to the expense of replacing them.

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[Happy Hummer]

Very informative thread so far.

 

[JPaul]

Finished pulling the engine today. Here's the culprit:

#6 cylinder intake lifter. Not totally sure what chewed it up like that, but the cam lobe is eaten up on the leading edge of the lobe just before max lift.

 

[JPaul]

I went back out and cleaned off the oil and gave it another look. All the needle bearings are there, so it wasn't that. I noticed that there is a flat spot on the roller though. The cam lobe is chewed up from open to close positions as well. Poking around in Google I found this blog post that has a pic of lifters and cam with similar damage:

http://www.gidcumb.net/jerrysblog/gm-active-fuel-management-headache/

He mentions that it is caused by the lifter slapping against the cam lobe, which considering the lifter had a tick previously sounds about right. I found a couple other posts with similar damage.

 

[alrock]

Glad you got it diagnosed!

 

[mdocod]

Normally I think we'd say something about how important it is to adjust valve lash as engines wear.... but I believe the 5.3 has hydraulic lash adjusters.

My rodeo has a notoriously noisy (clackity) valvetrain caused by a number of factors, the primary being that the pivot shaft for the rockers in the SOHC design doesn't get enough flow/lubrication to the last few rockers on the passenger head near the firewall. Over the years, this wears out the pivot shaft, causing the whole rockers to slap a bit as the engine runs. The rest of the valves all have some clatter too as these engines age just from the hydraulic adjusters no longer working as well, which can be caused by a number of things, primarily varnish buildup on the wheep hole.

My rodeo started making valvetrain noise within a few thousand miles of buying it (~140K miles). I used fancier oils in it through most its remaining life and it continues to run today with about 250K on that original engine still making noise but hasn't failed. Being a direct acting valvetrain, I avoided oils with reduced boundary lubricating additives, sticking with oils designed to produce thicker films and leave behind more barrier lubricating additives. The 5.3 shouldn't need this with rollers in the valvetrain, but I'm of the opinion that the "ideal" conditions they figure on for which oil is good for an engine, can't be counted on through the life of a vehicle and all the unexpected conditions the engine may have to run in, like being overheated, run low on oil, started at -35F, or simply, the effects of a oil leaving varnish behind over the long haul.

I can't say for certain if lube choice had any impact on my rodeo engine or your engine, but I'll treat my H3's 3.7L to the same treatment of nicish oils. I like 5qt jugs of whichever 0W-40 A3/B4 is on sale at walmart. Doesn't cost much more than regular oil but gives me some peace of mind.

Anyway... I'm rambling pointlessly about oil... I'll just get to the meat of my curiosity. What kind of oil has been in this engine most of its life, and how often was it changed? On the other cam lobes, is there surface varnish or are they clean?