Help to identify top end noise

gmcman

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Dec 12, 2011
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Sounds like it's coming from the valvetrain...could be a bad lash adjuster. Sometimes when I start it I will get a noticeable, .much louder tap, tap, tap...might last a few seconds, or close to a minute. However....if it does tap, as soon as I shut the motor down and restart, it's gone. No noise upon restart.

This is a video of the noise when warm. Could be part of the cold start noise, but if I just tap the gas, enough to bring it off idle to about 900 RPM, the instant it begins to rev, the noise goes away then settles back into a light tap.

I dont know if that's a lash adjuster, timing chain tensioner, or maybe the cam phaser.

The CPAS is clean.

I thought maybe the cam phaser only because it gets quiet the moment it stars to rev, but the noise seems to be near the #2 cylinder.

Hard to say, but let me know if anyone has had a similar noise and possible remedy.

 

Mooseman

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Dec 4, 2011
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Is it a really regular tapping or irregular? Can you feel something at the front top of the valve cover? Do you think it could be the timing chain tensioner? Think the chain is flopping against the top chain guide? It sounds almost like a knock but very irregular. When mine went, it made irregular noise only at idle and would stop as soon as I revved it because the oil pressure would put tension on it.

A regular tapping could be a lifter.
 

gmcman

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If I put it in gear and load it up, it's dead quiet. It's definitely happening at cam speed and is in the top of the motor. That being said one can argue it's happening on the power stroke but it appears to be in the top.

The cell video seems to give a hint of a lower tone but it's a little bit higher pitched.

Hard to pinpoint the noise, these blocks send noises everywhere, don't really feel anything on the plastic cover.

I recently ran a couple cans of Liqui Moly hydraulic lifter additive with some MMO, and this quieted the noise a little. Odd that it could be varnished as it had Mobil 1 most of its life.
 

littleblazer

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Jul 6, 2014
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Sounds like valve noise to me. Like a diesel.
 
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Mooseman

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I think there's a trick to check.for.lifter noise by plugging the valve cover crankcase vent hose to.increase pressure in there. Not sure exactly what it means if the noise stops with that buildup of pressure.
 

littleblazer

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Jul 6, 2014
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I think there's a trick to check.for.lifter noise by plugging the valve cover crankcase vent hose to.increase pressure in there. Not sure exactly what it means if the noise stops with that buildup of pressure.
Higher delta P and thus more oil pressure? Leaky lifter is better with more I guess?
 

gmcman

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Dec 12, 2011
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I think there's a trick to check.for.lifter noise by plugging the valve cover crankcase vent hose to.increase pressure in there. Not sure exactly what it means if the noise stops with that buildup of pressure.

I remember doing that a couple years back...been going round robin with this noise but sometimes it's barely noticeable.

Yes, if I plug the port, the vacuum I believe pools the oil and the noise stops. Is that the known procedure to determine a bad lifter?
 

m.mcmillen

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Apr 29, 2016
554
Wisconsin
I remember doing that a couple years back...been going round robin with this noise but sometimes it's barely noticeable.

Yes, if I plug the port, the vacuum I believe pools the oil and the noise stops. Is that the known procedure to determine a bad lifter?

I don't think it determines a whole lot. I could do the same thing and it would make my engine stop knocking.
 

gmcman

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I don't think it determines a whole lot. I could do the same thing and it would make my engine stop knocking.

When I first saw that happen, I was also thinking it provides such a high amount of negative pressure in the crankcase that it possibly pulls the pistons down just enough to take up any gap from the rod bearings upon the start of the power stroke..... thus possibly reducing the amount of audible knock.

That's just a wild hunch.
 
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littleblazer

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When I first saw that happen, I was also thinking it provides such a high amount of negative pressure in the crankcase that it possibly pulls the pistons down just enough to take up any gap from the rod bearings upon the start of the power stroke..... thus possibly reducing the amount of audible knock.

That's just a wild hunch.
The momentum of the rod moving around is probably way higher that that. My guess. Magic!
 

gmcman

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The momentum of the rod moving around is probably way higher that that. My guess. Magic!

Well, I was thinking it would only be applicable at TDC and shortly after. In theory it holds some water, but in practicality I agree there are other stronger forces working against it, but....vacuum is a powerful thing, especially at almost 20 in Hg.

The way it behaves when cold sometimes, I'm 99% convinced its in the valvetrain.
 

littleblazer

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Well, I was thinking it would only be applicable at TDC and shortly after. In theory it holds some water, but in practicality I agree there are other stronger forces working against it, but....vacuum is a powerful thing, especially at almost 20 in Hg.

The way it behaves when cold sometimes, I'm 99% convinced its in the valvetrain.
Funny you say that, pretty much every engine I've torn down (all two of them) the wear is worse on the top bearings, making me think the knock would be occurring on bdc. Strange how things are sometimes. Iirc, pulling the plug wire on a rod knock makes the noise go away. It's been a while.
 

gmcman

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So I dove into this a little today and when I said I could plug the top port on the valve cover and stop the noise...that was awhile ago.

Today I tried it and there was minimal suction...barely any.

I removed the molded PCV hose on the intake and I have strong suction on top as I should, but from the lower port to the top of the valve cover....I barely have any.

I put a vacuum cleaner on the lower PCV port briefly and there is barely any air entering the top of the valve cover.

So I assume this points to a possible clog? I wonder if it's near the top port in the valve cover..or maybe that's normal but I doubt it.
 

gmcman

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Dec 12, 2011
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Ran a few ounces of seafoam in the lower PCV port in hope's to loosen something up. Tried some low pressure compressed air both top and bottom, I did get some airflow restored.

Drove it around and that seemed to be one of the major culprits...a restricted PCV system.

I had a oil catch can and while it worked, likely restricted the vacuum enough to slowly clog the system. The hoses on the catch can were not restrictive, but it was the only mod I had done to the PCV.

Will post pics later, but it's much quieter now.
 

gmcman

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Dec 12, 2011
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This was a cold start this morning, even quieter. Hard to hear but sounds like a weak lash adjuster still...that's been the same for quite awhile.






This is in the afternoon after a warm up.

 

Mooseman

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Dec 4, 2011
25,257
Ottawa, ON
My old '02 sounded like that, maybe even worse. Just drove it till the tranny went.

Could be the oil. Different oil brands or types can affect it.
 

gmcman

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Dec 12, 2011
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So I was poking around the motor again today, the noise gets quieter when warm so I was looking for maybe an exhaust manifold leak or just something I could hear with the stethoscope.

I've disconnected one cylinder at a time and not much difference...if any. Today I disconnected one cylinder at a time but placed the stethoscope on the coil pack bolts and listened while the cyl was active and when inactive. I could clearly hear a slight knock on the #4 coil pack bolt and it went away when I deactivated that cyl.

This is barely audible outside, and not audible under load. It could be the onset of a rod bearing or a worn skirt.

My plan is to pull the oil pan and check the bearings. My question is....do I really need to remove the steering rack? Can I get the pan off with the rack in place?
 

Mooseman

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Dec 4, 2011
25,257
Ottawa, ON
Maybe it's a kind of piston slap?

I had to remove the R&P because the crossmember has to come down. You also have to pull the axles and unbolt the diff (if 4x4) and unbolt the A/C compressor. I wouldn't pull the pan for this. If it was a bearing, I would think it would be noisier when hot as the oil would be thinner. However, piston slap makes sense that it would quiet down when hot as the piston expands.
 

gmcman

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Dec 12, 2011
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I changed the oil this am so I will drive it awhile today and take another listen. It could be piston slap...and safe bet I could have some skirt wear @ 287K.

I have to change the front diff to oil pan seal and replace the splined disconnect anyway. My gut is saying it could be the rod only because the noise is a quick, solid, tap but not a high-pitched tap nor a deep throaty knock...kinda in between, which could be the very early stages of a failing rod bearing.
 

m.mcmillen

Member
Apr 29, 2016
554
Wisconsin
I pulled an oil pan on one of these once and I don't recall pulling the rack and pinion completely. I think I just unbolted it and tied it up out of the way.

In regards to your noise, I had almost identical symptoms that you're describing with my engine. The noise eventually got to where it would not go away, even when warmed up. I found scuffed up pistons. One was bad enough to score the cylinder wall a bit. I found that all of the bearings, both rod and mains, had very little wear.

Something you could do to get an idea of what is going on without going through the trouble of tearing it apart is to get your oil sampled. I use Blackstone Laboratories https://www.blackstone-labs.com they will send you a free sample kit.

Edit: I added a copy of an oil analysis so you can see what they tell you after you send a sample.
 

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Mooseman

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Dec 4, 2011
25,257
Ottawa, ON
Another thing you could do to is check for scuffing in the cylinders with a boroscope. The oil analysis is a good idea but you'll have to wait until the next change since you changed it unless you still have the old oil.
 
Dec 5, 2011
574
Central Pennsylvania
Be careful sending used oil that has been "stored". Blackstone's (and presumably any oil analysis) is extremely sensitive - to the point of picking up silicon from permatex used to secure a gasket months beforehand. This is why I didn't send my oil - I found out about them after I changed my oil. I still have it, but the "grit" that falls into the catch pan and the fact that I use the same pan for changing everything is why I haven't sent it. I'd get misleading results like "antifreeze in oil" from changing my waterpump using that catch pan and metal flakes from changing diff fluid.
Oil analysis is awesome - but it has to be sampled correctly to be accurate.
+1 for the borescope, though. I've been looking for one. A couple Christmas's ago, Lowes had them for cell phones but I haven't seen them there in quite a while. I've found them online for as little as $10 since but am dubious of the quality at that price.
 
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mrrsm

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FWIW... have a look at my "Flickr-Bucket" on the Complete Tear Down of a 2004 4.2L Engine with around 160,000 Miles in its history. The engine was well cared for... but as you can see from the images of the Cylinder Walls... at the point just before and after Top Dead Center... as @m.mcmillen 's image showed... the Pistons hover momentarily at TDC during "Piston Dwell" as the Connecting Rod swings forwards in a clockwise direction underneath... and this causes all of the Pistons to rock back and forth...effectively wiping enough oil off of the Cylinders near the top and allowing the two Compression Rings to erode their way into those Cylinder Wall areas.

43478720011_f37b0e1c47_z.jpg

GM42LCYLIDERSCORING.jpg

As mentioned already by "The Legendary Mac"... in this Motor... there was only the slightest amount of wear on the Main and Con-Rod Bearings present. These images will give you a better idea of how these things look in plain sight. In Colder Climes... the delay in having immediate lubrication on the Cylinder Walls and the tendency for most owners to avoid using the recommended 0W-30 Winter Motor Oil will exact a price in creating Piston-Rock (Slap) evident in higher mileage vehicles much sooner than later.

 
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gmcman

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Awesome....thanks for the pics...I'll check them out.

I drove it to work, honestly, I need to get all the little noises fixed first before I determine if it's a rod or skirt, or something else.

1. There's a slight lash adjuster noise.
2. Small exhaust leak on top of muffler
3. Rear exhaust manifold bolt is broken...been like that for years..haven't heard much coming from it.
4. Light piston slap when cold
5. "Possible" rod knock on #4 but I could also have a cracked exhaust manifold.

I'm going to check the exhaust manifold as well as repair the muffler. Will try to get the bolt out and seal that area up.

When listening near the passenger tire, it really sounds like a resonant noise from the heat shield during the tapping or knocking noise.

I really have a 5-piece band playing under my hood even though it's not that noisy...too many sounds so it's hard to pinpoint.

If I'm stopped In gear and power brake the trans to 2000 RPM, I don't believe I hear any knock. This kinda possibly rules out a rod but not entirely.

I surely dont want to pull the pan before I get the rest figured out...just don't want to wait too long if in fact it's a rod bearing.

Any suggestions on exhaust manifolds? I'm going to check it first, but may want to have one next to me if I have to swap it. Weekends are tight and time is precious.
 

Mooseman

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Dec 4, 2011
25,257
Ottawa, ON
The aftermarket has improved manifolds (Dorman is one). I had two that were cracked right at the Y between cylinders 5 & 4.
 
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mrrsm

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Sometimes... you can get a better feel for the sounds under the Valve Cover if you open the Oil Filler Cap ...start the Engine when Cold ... and then listen at the opening to the interior upper engine head ...and record the sound from that position. These engines have 24, non-adjustable, VERY short, hydraulically activated Valve Train Push Rods that have been known to shatter from time to time. This video shows the Bench Top Assembly of the Exhaust Side Valve Train on a GM 4.2L Engine Head that displays great views of the assembly of these tiny and often delicate components:


In regards to Diagnosing Pulsating or Thumping Rod-Knocks... They present themselves more when the Engine is at Idle than when under the Dynamic Loading of a rapidly rotating Crankshaft. This is because at higher RPM... any Con-Rods with Loose Bearings or Play tend to get grabbed by the Crankshaft Journal at high speed and NOT given the opportunity to go slack enough to rattle around inside of the larger space within the errant Journal.

Think of this sensation as though you have experienced when under hard acceleration as you are pinned against the seat... but as soon as you let off the Gas Pedal... you can lean forwards and backwards with freedom and ease... the same thing happens in this case... but with Angular Momentum imitating Gravity to pin the Con-Rods to the Crank Journals and thereby quiet down the engine at higher RPM.

I suspect that if your Maintenance Schedule concerning the use of Mobil1 5W-30 was happening regularly around every 3,000 Miles... the likelihood of that motor suffering any serious damage to the Bottom End is very unlikely. If you manage to take another Video while holding the Camera down below and under the Engine Compartment and Wheel Well areas... you could better identify, isolate and eliminate any major problems with "The Bottom End".
 
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littleblazer

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Jul 6, 2014
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At least it doesn't have the random tick mine does.
 

gmcman

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Dec 12, 2011
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Thanks for all the insight...much appreciated. I did change out a lash adjuster a few years ago but didn't have the Kent Moore tool so this time is was much easier.

Something I noticed this time is while I was bumping the starter, I didn't get any oil flowing from the lash adjusters. Last time I was able to see a small pooling around them. I cranked the starter for about 20 sec just to see and there was no oil.

IIRC, I did see oil last time if the starter ran for about 5 sec.

The motor is quieter on the top now, cold start this am showed no ticking, I do have something going on though in regards to a deep tap, could be a knock...but not sure.

This noise was there before changing the lash adjusters, but overall the motor is quieter.

I will need to check the oil pressure again at idle but it quiets right up when started. I'm confident I'm getting oil up top at idle but could be a reduced flow.


Pic of the valvetrain @ 288K Miles

Screenshot_20190407-143210_Gallery.jpg

Screenshot_20190407-143234_Gallery.jpg
 

mrrsm

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That is the CLEANEST Top End in ANY GM Atlas 4.2L Engine that I have EVER seen to date... so there can be absolutely No Question that your engine has received excellent, scheduled maintenance with timely, Top Quality Oil and Filter Changes for its entire operational life.

The other encouraging thing is that IF your engine head innards were coated with Gas Gum and Dark Carbon Residue... it would be proof positive that the motor was suffering from Worn Rings and Excessive Combustion Blow-By ...which does not seem to be in evidence at all with your Motor.

But the actual confirmation of having nominal Min-Max Oil Pressure of 12 PSI to 65 PSI and Good Compression must involve performing an Analog Oil Pressure Test via @MAY03LT 's Great Video on how to do that task... and as always brought up by @Mooseman... performing a Dry-Wet Cylinder Compression Test as well:

 
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gmcman

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Thank you for the kind words. I will try to get an oil pressure test done, I also bought a set of rod bearings just in case they have worn.

I will also get a good cold start video and hopefully we can pinpoint the noise.

Could be an exhaust leak, or likely skirt wear. If the rods do need bearings I would want to attack that sooner than later.

All 6 intake ports look the same, but that doesn't show the chambers.

Screenshot_20190407-155046_Gallery.jpg
 

mrrsm

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Because your Atlas Engine is open and exposed... now would be a good time to investigate Loose Con-Rods by following this simple, definitive, non-destructive and none-invasive test:

 

gmcman

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In regards to Diagnosing Pulsating or Thumping Rod-Knocks... They present themselves more when the Engine is at Idle than when under the Dynamic Loading of a rapidly rotating Crankshaft. This is because at higher RPM... any Con-Rods with Loose Bearings or Play tend to get grabbed by the Crankshaft Journal at high speed and NOT given the opportunity to go slack enough to rattle around inside of the larger space within the errant Journal.

That does make sense....the last motor I had a rod issue with was an Iron Duke 2.5L and when cold it was quiet but within a few minutes, the knock would start but didn't dissipate too much at higher RPM....but did quiet down when revved. The noise progressed quickly over the course of about 1K miles...fresh set of rod bearings breathed new life into it.

I will definitely try to get a good video tomorrow afternoon. The top end appears to be quiet, seems when warm there's a faint knocking sound, honestly it's hard to tell if it's a manifold leak or a rod.

The noise almost seems louder on the passenger side which gives hope it's a manifold but the tapping sound is just too close to what would sound like a rod.

Like stated before, if I put in gear and load it up a little the noise is quieter if audible at all.

Basically starts quiet, then somewhat chatty, and as it warms up, the noise dissipates slightly but doesn't completely go away.

Sorry to ramble on, hopefully a video clip will help.
 

mrrsm

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If you start to "Get Into The Weeds" with conducting either a partial or complete Atlas Engine Re-Build... drop in at these links to my Threads on what started as an Engine Head R&R ...and quickly disappeared down a Rabbit Hole towards deciding upon an Engine Swap (...which is NOT indicated HERE concerning your Motor).

Due to some unreliability issues with my Photobucket Account... I recently transferred a large number of Photo Albums with many hundreds of images concerning the GM Atlas Engine Repair over to a new "Flickr-Bucket" Account. This first link to all of those Albums is a good place to start if you want OEM Part Information and Part Numbers including Box Ends with lots of data. There are quite a few of these Albums there that cover the 2002 as well as the 2004 GM 4.2L Engines...so look each of them over... you will be surprised how much time it will save you in locating the information you might need when the time comes to Order Parts:


I'm also suggesting that you check these other two links out as well, for no other reason than a speed read over Pages (1) and (2) for some VERY Detailed information about the Make-Model & Part Numbers necessary to know for performing this task to assist you; regardless of how deep or shallow things become as your repair goes forward:

Please note that I cannot recommend reading these Threads entirely to their completion...as the Best and Most Direct Information for this kind of Engine Repair is available in Threads completed succinctly and brilliantly by @m.mcmillen and @Mooseman:


 
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gmcman

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I apologize for not getting a video posted, but so far the cold starts have had zero lash adjuster tick.

I had some Rislone in the fresh oil and ran that for about 500 miles. I looked into one of the cylinders and found some carbon on the piston crown. This morning when I got home, I was under the hood and was hearing a light knocking that was eminating from the intake. The noise had that hollow plastic sound, it bugged me since I know the intake is fine and theres no gasket leak.

So I figured it may be some light carbon knock so I raised the RPM to 1800 and ran about 12oz of hot water into the vacuum port if the TB.

Once I returned it to idle, it seemed after a few moments that light knocking noise had diminished greatly.

Couple that with a loose exhaust manifold bolt in the front of #1 I tightened...the motor is pretty quiet now.

I switched to Pennzoil Platinum this AM and drained the oil after the water injection. I drove it around and really the only noise I hear is a very, very faint exhaust leak as I have 2 broken manifold bolts, but theres a single, light tap near the #2 or #3 cam lobes on the drivers side. This noise goes away if I plug the fresh air intake port in the valve cover.

I'm convinced there's a slight lack of oil flow to that area. If I rev it up slightly the tapping stops.

I still need to get an oil pressure test but given the mileage, what could be the cause of this? I thought the oil pump fared very well with mileage as it could be a spring or maybe a restricted passage.
 

gmcman

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A lot has transpired since this morning. From what was a clearly audible tick has been reduced to barely audible over the injector noise.

Overall, I'm quite surprised what the motor sounds like now as opposed to a week ago. So much that I'm not considering removing the oil pan as of now.

Will keep you posted....been very busy as of this week.
 
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gmcman

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Here's one of the noises that had me looking inside the motor. I was able to tighten the forward most exhaust manifold bolt for cyl #1 about 1/4 turn, both bolts were loose for that cyl but this really quieted the noise a lot.


I still have 2 broken manifold bolts and will try to get that fixed next weekend. There is still an exhaust leak and is audible in the 2nd video as well...almost a slight, hollow sound that sounds like tapping on the manifold heat shield.

The 2nd video is a longer video, this is a cold-start and shows it's current state. The motor is somewhat quiet in the beginning then the noises progress. I believe once the piston slap settles down, there is a slight mix of the manifold leak and what seems like a light tick in the valvetrain.

The new lash adjusters have quieted the valvetrain and has so far eliminated the cold-start ticking.

About 3 minutes into the video, I interrupt the current cold start video to show what I was hearing before the exhaust manifold bolts were tightened for cyl #1, and also I did a water injection cleaning due to the noise I was hearing from around the intake manifold. I thought it could be carbon knock and turns out it did make a difference.

Still not ruling out anything major, but overall it sounds like a different motor now.

 

gmcman

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Over the course of a busy 3 weeks, I've changed out the exhaust manifold which seemed to quiet down some of the noise, ran some BG EPR for 20 min in the crankcase, last tank had a bottle of Techron concentrate while awaiting my Amsoil Pi, and this tank has a bottle of Amsoil Pi.

I ran the EPR with the Pennzoil Platinum which had a bout 800 miles on the oil...I didn't want to wait to run the cleaner in case I had any build up in the ring packs, so I did lose out on some miles on the oil but I need to get this all figured out.

I received a better remote camera today than the one I had been using and will get some pics inside the cylinders. I was starting to lean on the possibility of some carbon knock since I did have that restricted PCV system for awhile, still unsure of what the chambers look like.

The motor runs very well after the exhaust manifold change. I cannot remember the last time I ever had 300 miles to the fuel light with my mix of 70/30 hwy/cty miles....averaging 18 MPG mixed, I believe I stated 18.5 in another thread but it was right about 18.2.

My last tank incorporated the 20 min BG EPR cleaning and 10 min of GM upper engine cleaner so the mileage at the fuel light was 292...both times the tank took 16.5 gal...so I'm stoked about that but hoping I don't need to really tear into this motor now.

After the new lash adjusters, manifold, cleaning chemicals, I have no cold start ticking...which happened after the replacement of all 24, but there's one noise that is starting to lead me to either a rod, possibly #2, and/or the skirt wear which could be some piston slap.

After returning home tonight, I took a quick video of the area around the AC compressor....not that the compressor is the culprit, but when the compressor engaged, the sharp knock seemed to quiet down considerably, but when not engaged, you could hear the knock.


Video taken tonight, you can hear the sharper knock behind the injector noise when the compressor kicks off.



This knock has me leaning me towards a possible rod bearing because if I disconnect the coil to cyl #2, that's the only cylinder that almost completely reduces the noise. If I look around the top of the motor, I tent to fixate around that area as well.

The knocking sound that remains when hot, doesn't start making itself known until about 3 min into the warmup, but remains. This noise is at cam speed so perhaps not a carbon buildup near the crown or in the squish area. I was thinking maybe one side of the chamber had a deposit and would cant the piston slightly causing a tap where the opposite side skirt would hit the bore....but I don't believe it would happen at cam speed, but every rotation.

After hearing this noise over the last week or so, it actually is audible from behind the glove box area inside the cabin, almost mimicks an exhaust leak...but I did check all the bolts. The noise seems sharper on the top, and more dull on the bottom. I did get a video but after listening on headphones and the speakers, the camera mic seems to exaggerate the noise a little so when I get the video posted, please note that it's not as loud and defined as it sounds but it's still clearly audible when next to the vehicle.

The noise is also more noticeable standing near the RR door than in front or next to the RR wheel opening.

Sorry for the delay on the other video, but I will have it up soon.
 
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gmcman

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Here's a few shots of cyl #2, this is at BDC. I was alarmed at the black cylinder wall at first but realized that was the reflection of the piston crown.

I'm guessing the piston to wall gap is excessive? Granted this is at the bottom of the bore but also means the skirt shares that gap.

The 90 deg mirror doesnt work very well but was able to get some scuffs in the frame.

Screenshot_20190505-131743_Gallery.jpg

Screenshot_20190505-131826_Gallery.jpg
 
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mrrsm

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Well now... That is a Damned Shame. Those images looks very much like what @mc.millen found upon the disassembly of his engine, too. This occurs from millions of Piston Rock events at TDC along with the Teflon Skirt Coatings getting worn away in High Mileage Engines. There is nothing that says that you cannot drive the vehicle for a while longer until you either locate a "youthful" in-kind Swap Motor, or choose some other rebuilding option. While I admire how straightforward your investigative technique has been in memorializing this definitive discovery with digital imagery, I am very sorry for the outcome... I wish it were otherwise.

The important thing to understand is that these GM 4.2L Cylinder Sleeve walls spec out to being only 1.50 MM Thick... and thus, they cannot tolerate much in the way of re-boring without creating additional problems. But, unlike many other engines, the Atlas Aluminum Engine Blocks CAN be brought back to an actual Factory Fresh condition by using a Special K&M Cylinder R&R Tool Kit along with (6) Replacement Chilled, Cast Iron Cylinder Sleeves machined to within just a smidgen of a necessary Plateau Hone that you would have to do yourself for a perfect sizing up of the Cylinder Wall Dimensions to the New Pistons. These R&R Cylinders are sold individually by Melling and are quite specific to the 4.2L Engine for around $30.00 per Cylinder.

This is the same K&M Kit being used on a Tiny Ecotec Motor...but the principle would be the same in the GM 4.2L LL8 Engine:


"The Legendary Mac' solved his problem though just by having his I-6 Engine Block lightly honed and then using the Stock as a Clock GM-MAHLE OEM Pistons, Wrist Pins, Ring Locks and MAHLE Ring Sets to overhaul his Motor. But... considering the age of your SUV ...it would still be an expensive repair to engage in yourself ...and 'off the hook' costly if you decided to obtain a Crate Engine for a Drop In Solution instead. Among all of these options... locating a Low Mileage, Running Engine would be the least problematic to accomplish yourself ...and a whole lot less hard on your Wallet.

While I am NOT encouraging you to follow suit or choose this repair path as your First Choice... If you want more information about the K&M Cylinder R&R Kit and its use... visit my 2002 -2004 Engine Swap Thread at Post #134 here:

 
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