<FIXED> Lifter noise & dull knocking (bottom end?) troubleshooting

[Capote]

So I've got loud lifter noise in my engine, been going on a week now? Cannot find the culprit, and as of two days ago I noticed a dull knock too. I at first thought it was a vacuum leak or exhaust leak, but I have checked everything I can think of and I cannot feel any air or exhaust escaping either. I have a block off plate that used to leak, but no exhaust is escaping from it this time. I fear that I may have some sort of issue with cylinder 1 (no codes though). I used a stethoscope to try to pinpoint where the dull knocking I hear is coming from as well as specifically which cylinder the lifters are noisiest around. Everything is pointing to cylinder 1. I used my knuckle to feel for the vibrations consistent with the knock and it's indeed coming from there. When I unplug that coil pack the knocking vibration goes away. Yeah, even though the engine is shaking due to a cylinder not firing when I do that test, I can still tell that the vibration I was feeling ceased. Lifters are noisy regardless. I believe as of now the knock mentioned above is coming from the bottom end. It's dull and hard to hear over my exhaust and the engine, but it's there. I can only hear the knocking if I listen in closely or if i'm laying down next to my truck with my head underneath.

-oil level is normal
-RPMs at idle normal
-only driving habit I've changed recently was driving in 3rd in town

Brandon isn't here this weekend to consult with in person, so I've had to text him, he's unsure without taking a look for himself. If I find out I've got a rod knocking for sure, is it worth rebuilding with a rebuild kit or should I just go and swap in another 4.2? Like an '08? That year 4.2L had 285hp. I've looked at a few online that were alright prices I guess. 5.3 is out of the question, barely anyone has done a full swap and documented it, not to mention it's pricey to get everything needed to properly swap it over. AND this is my D.D., i'd sell my Cutlass to do the swap.

 

[Sparky]

Happen to have any audio?

These engines technically don't have lifters because they are DOHC, but there are still valvetrain components that could tick if something was worn/broken such as a valve spring (my Camaro is suffering from that right now).

Thudding from down low sounds like it could be a rod but could be something else, not sure. What year is your truck again? I know you can put later year engines in earlier years to a point but there are some things that either need to swap over from the old engine or extra stuff needed to make the newer one work in the older model. I forget what exactly.

 

[Capote]

Happen to have any audio?

These engines technically don't have lifters because they are DOHC, but there are still valvetrain components that could tick if something was worn/broken such as a valve spring (my Camaro is suffering from that right now).

Thudding from down low sounds like it could be a rod but could be something else, not sure. What year is your truck again? I know you can put later year engines in earlier years to a point but there are some things that either need to swap over from the old engine or extra stuff needed to make the newer one work in the older model. I forget what exactly.

No, I don't have any aftermarket audio equipment.

When me and Brandon replaced my valve cover last year, we inspected all those components, replaced the lifters (even though they were fine) and the valve springs were in good shape. I still have a bag of new ones though since they never had to be used.

Mine is an '04, I don't recall what all changed from '04 to '05 and up. I know there were a few minor changes. That became apparent to me and Brandon the first time we met up and worked on our rigs together.

 

[Sparky]

I meant audio of the thudding/tapping, not vehicle sound system

 

[Capote]

I meant audio of the thudding/tapping, not vehicle sound system

Haha! Wow..................................................I was wondering why you were asking that.
Nah man, you'd never hear it on a video or audio recording. I wouldn't be able to pick up the noise properly.

 

[Sparky]

My experience with rod knock was with a different engine (3800 series 2), but when it was knocking it was a very obvious thud thud thud, and it would go away if I revved up and let off the gas. While the engine speed would drop down it would stop thudding until it came back to idle. The first one lacked power too, the second one you could almost feel the friction in the engine at idle because the oil pressure dropped so low. (Same car, incorrectly done install caused the used engine to spin rod bearings too, replaced via warranty with another used engine which was knocking almost immediately, replaced again under warranty and that 4th engine ran like a dream lol but what a pain that was.)

 

[Capote]

My experience with rod knock was with a different engine (3800 series 2), but when it was knocking it was a very obvious thud thud thud, and it would go away if I revved up and let off the gas. While the engine speed would drop down it would stop thudding until it came back to idle. The first one lacked power too, the second one you could almost feel the friction in the engine at idle because the oil pressure dropped so low. (Same car, incorrectly done install caused the used engine to spin rod bearings too, replaced via warranty with another used engine which was knocking almost immediately, replaced again under warranty and that 4th engine ran like a dream lol but what a pain that was.)

I've noticed no performance issues. I'll have to check on Dash Command for oil pressure readings. My truck's exhaust is too loud to really tell if the knocking ceases at a certain point or is consistent with the engine speed. Not to mention the lifter noise is louder than the knock anyway. Maybe if I had someone under my truck listening for the subtle knock they could tell, but by myself it's not do-able.

 

[Sparky]

Unless you have an aftermarket oil pressure sensor you won't have much to go by. These 4.2L engines have a dumb pressure switch remember, so it doesn't actually give you a reading which sucks for troubleshooting.

 

[Capote]

Unless you have an aftermarket oil pressure sensor you won't have much to go by. These 4.2L engines have a dumb pressure switch remember, so it doesn't actually give you a reading which sucks for troubleshooting.

I'm aware that the oil pressure on the cluster is a dummy, but I can still read what it's actually at through Dash Command though.

 

[Sparky]

It isn't so much the dash gauge that is the dummy as much as the input to the PCM being just "on/off" and the PCM then fabricates the reading from an expected base PSI + "x" increase for RPM increase and pushes that to the gauge.

If Dash Command is reading the PCM data it is getting the fabricated number same as the gauge on the dash. That's why I asked if you had an actual oil pressure sensor installed somewhere.

 

[Capote]

It isn't so much the dash gauge that is the dummy as much as the input to the PCM being just "on/off" and the PCM then fabricates the reading from an expected base PSI + "x" increase for RPM increase and pushes that to the gauge.

If Dash Command is reading the PCM data it is getting the fabricated number same as the gauge on the dash. That's why I asked if you had an actual oil pressure sensor installed somewhere.

Wow, GM just can't do something so simple as to give an actual reading, even from the OBDII?

I do not have an auxiliary oil pressure sensor unfortunately.

 

[littleblazer]

I have a rather quiet knock when warm. You just barely hear it. Honestly it sounds more like piston slap... in lines are known to do it. The iron duke in my boat (3.0l 4 banger) has a very similar noise. Do you notice it when you first start it? Actually, I'll go get some video of mine with a mic and you could see if it's similar.

For the lifter noise, cover the little hose from the valve cover to the intake box. ( I know you don't have it any more but the front one) and see if it goes away after a minute. That should pressurize the crank iirc.

 

[Capote]

I have a rather quiet knock when warm. You just barely hear it. Honestly it sounds more like piston slap... in lines are known to do it. The iron duke in my boat (3.0l 4 banger) has a very similar noise. Do you notice it when you first start it? Actually, I'll go get some video of mine with a mic and you could see if it's similar.

For the lifter noise, cover the little hose from the valve cover to the intake box. ( I know you don't have it any more but the front one) and see if it goes away after a minute. That should pressurize the crank iirc.

The lifter noise and dull knocking underneath are noticeable upon start up, just a little quite at first until the engine is at normal operating temps. Yes I've done that test, crankcase is pressurized still. There's an obvious vacuum occurring when I unblock it.

 

[littleblazer]

The lifter noise and dull knocking underneath are noticeable upon start up, just a little quite at first until the engine is at normal operating temps. Yes I've done that test, crankcase is pressurized still. There's an obvious vacuum occurring when I unblock it.

Does it quiet down when you do that?

 

[Capote]

Does it quiet down when you do that?

Never did on all three occasions.

 

[HARDTRAILZ]

Why not go for the 291 HP version if you need an engine? Mine has treated me well.

 

[Sparky]

The lifter noise and dull knocking underneath are noticeable upon start up, just a little quite at first until the engine is at normal operating temps. Yes I've done that test, crankcase is pressurized still. There's an obvious vacuum occurring when I unblock it.

At startup? Does it go away after it warms up or get louder?

 

[Capote]

Why not go for the 291 HP version if you need an engine? Mine has treated me well.

Too much money for other components that come along with a v8 swap

At startup? Does it go away after it warms up or get louder?

No, never goes away or lulls down. Consistent noise

 

[littleblazer]

Too much money for other components that come along with a v8

The 291 is an i6.

 

[HARDTRAILZ]

Stock I6 in my 06

 

[littleblazer]

I think they're identical but they de-rated the hp for the thermal clutch. I could be wrong. You have a MAF right?

 

[HARDTRAILZ]

Yup. I do not think accessory matter on the HP ratings.

 

[littleblazer]

Hm. Thought they tested as is.

Anyway @Capote any drive ability issues or shimmys or anything? Only reason I ask is because if pulling the coil pack made it go away that makes zero sense in my mind. I would think it would make more noise. My truck sounded like a blender filled with rocks when #3 went out.

 

[HARDTRAILZ]

Did you try swapping the plug and coil pack around and see if things changed to another cyl?

 

[Mounce]

Also with having it narrowed down to one cylinder do a compression test.

 

[Capote]

Anyway @Capote any drive ability issues or shimmys or anything? Only reason I ask is because if pulling the coil pack made it go away that makes zero sense in my mind. I would think it would make more noise. My truck sounded like a blender filled with rocks when #3 went out.

You did not understand my statement... Obviously pulling a coil pack makes the engine rock around and sound like crap. Yes it did that, but while it was doing that I could tell that the vibration in question was gone. It's hard to explain.

Did you try swapping the plug and coil pack around and see if things changed to another cyl?

I haven't only because I believe the issue to be internal

 

[mrrsm]

FWIW...I've been thinking about your initial post for a while now watching others respond...and it occurs to me that since you have narrowed down the sound to the front #1 cylinder area that this is actually very encouraging. Perhaps the problem is not a connecting rod issue... but one or more of the bearings in either the Water Pump or the Alternator. Recently a video done by @MAY03LT has become very popular for viewing because his diagnostic approach singled out the very scary noises you are hearing as being the alternator. The other reason to view this is at the very least... you can compare the racket from your own engine to his during the before and after sessions when he pulled the Serpentine Belt and started the engine:

 

[Capote]

FWIW...I've been thinking about your initial post for a while now watching others respond...and it occurs to me that since you have narrowed down the sound to the front #1 cylinder area that this is actually very encouraging. Perhaps the problem is not a connecting rod issue... but one or more of the bearings in either the Water Pump or the Alternator. Recently a video done by @MAY03LT has become very popular for viewing because his diagnostic approach singled out the very scary noises you are hearing as being the alternator. The other reason to view this is at the very least... you can compare the racket from your own engine to his during the before and after sessions when he pulled the Serpentine Belt and started the engine:

I watched the vid and the noise level of that alternator is way louder than the two noises I am hearing. I doubt I could pick it up on video. The "knock" underneath is hard to hear because it's so dull and my exhaust is loud even at idle. The noise up top is more of a lifter or worn out valve spring noise as far as I know. Good find with that vid of @MAY03LT 's. I will do that same test regardless though this weekend. I'm literally checking anything at this point. Hell I even checked my Flywheel bolts to see if one was loose causing a knocking sound underneath, I had that issue once.

 

[mrrsm]

The one thing to be mindful of is that since the "pushrods" in the Atlas LL8 are only say 1 1/2" long and fairly solid due the DOHC-OHV design with four valves per cylinder... you could have broken or shattered one or more of the thin metal rocker arm(s) in the top of the head for the #1 cylinder and if the thin valve stem collapsed from a failed spring keeper... the valve might have dropped inside the top of the combustion chamber just a bit...and after being struck by the ascending piston head...bent...and then got lodged inside the head. This can account for a banging noise each time the piston makes contact. This would not be the first time this has happened to the 4.2L Engine with 270 to 291 horsepower possible inside this bizarre six cylinder motor.

Here is a short video of some poor, quizzical soul in a similar situation who found just such a problem. In his case... I am suspecting that he over-revved the motor and "floated" the Valve Springs to cause this to happen...but due to the very thin metal parts used to minimize the mass in the valve train...these parts appear to be more delicate than we might think:

 

[Capote]

The one thing to be mindful of is that since the "pushrods" in the Atlas LL8 are only say 1 1/2" long and fairly solid due the DOHC-OHV design with four valves per cylinder... you could have broken or shattered one or more of the thin metal rocker arm(s) in the top of the head for the #1 cylinder and if the thin valve stem collapsed from a failed spring keeper... the valve might have dropped inside the top of the combustion chamber just a bit...and after being struck by the ascending piston head...bent...and then got lodged inside the head. This can account for a banging noise each time the piston makes contact. This would not be the first time this has happened to the 4.2L Engine with 270 to 291 horsepower possible inside this bizarre six cylinder motor.

Here is a short video of some poor, quizzical soul in a similar situation who found just such a problem. In his case... I am suspecting that he over-revved the motor to cause this to happen...but due to the very thin metal parts used to minimize the mass in the valve train...these parts appear to be more delicate than we might think:

Holy hell!!! That scared the hell out of me man! Me and Brandon hated just having to replace my valve gasket a long time ago. We never wanted to do any top end stuff again after that. I don't wanna take the valve cover off and find nothing. I don't have money to spare for rocker arms and etc either....

Damn guys. I'm hoping its something I'm just overlooking.

 

[Mounce]

Compression test will rule out dropped valve. That or point to it and/or a bad piston.

 

[Capote]

Compression test will rule out dropped valve. That or point to it and/or a bad piston.

Just read up about it. I have barely any chances do any of this. I work 6 days a week, 2nd shift.

 

[therealsethallen]

Sounds similar to what happened when my truck. When we tore down the old engine to see what the culprit was, it was discovered to be a bad intake valve on Cyl-6. It began as a misfire but the engine was never quite right afterwards, it started consuming oil. Which I neglected to even check, eventually it spun a bearing. 2004 wasn't one of the years I recall having valve issues, maybe you'll get lucky.

 

[mrrsm]

Batman... Listen ...Please... I did not intend to inflame your already justified high level of concern... But mentioning this potential...and hopefully unlikely possibility early seems important; should everything else on the Problem Check Off List fail to disclose the problem and a simpler solution prevail. The Compression Test on this engine is fortunately very straightforward and especially so if your confidence is high that the #1 Cylinder is the Prime Player here as access is immediate upon removing the #1 Coil On Plug, removing the Spark Plug and inserting the compression tube via spark plug like thread; topped off with an "O" Ring with the Compression Pressure Gauge attached and proceed with the test. Details abound on Youtube with How-Tos to get the most reliable results and once done, the test will be definitive.

In the mean time...if you think the engine is in immediate danger of a catastrophic internal component breakdown... I'd like to suggest that you drain your oil... replace the Oil Filter...and Autopsy the Old Oil Filter in a bucket partially filled with fresh Kerosene. Then run a magnet on a string around the inside of the bottom of the bucket for Ferrous Metal particles...and after draining the largest portion of the kerosene into a seal- able jar... pour the remaining contents of the bucket through a a Large Coffee Filter and search for Non-Ferrous metals... copper, aluminum ...essentially your search is for the remnants of any Babbitt Bearing material. If you discover nothing in the way of metal... that will be at least a good start and perhaps minimize the threat of any impending rod bearing damage.

Last but not least... I would suggest that you make a direct request for help to Drew @MAY03LT and seek his advice... knowing that he will probably ask you to post several videos with the engine idling... while moving the camera around to pick up any sounds from the front... and from the sides and from underneath the vehicle. As a military man with considerable experience... you know how important it is to ACT... rather than REACT... and doing these things in an organized, pro-active manner will get you closer to solving the problem.

 

[Capote]

Lol you've got a way with words dude.
Compression test is for sure happening as soon as I have ample time. I do not think that I am going to have catastrophic failure. I have no performance issues and no behavior from my truck reflecting such. I can WOT pull hard down streets all day and my truck will run like a charm. I do 100mph runs home at night and once I get into town and hit a red light, no funky idling or odd behavior from the truck. Its just time for a throttle body cleaning is all.
As for the draining of oil, I'll have to check my records to see what miles the truck had when I did it last. Was only last month. But first, the compression test once I have time and rent a kit.

 

[mrrsm]

Observing Credit to @Mounce here for the original suggestion on Performing a Compression Test to either confirm or eliminate this as the problem:

Harbor Freight has this $30.00 offering for a Quick-Disconnect Compression Test Tool Kit:

http://www.harborfreight.com/catalogsearch/result?q=quick-disconnect+compression+tester

And here is a Youtube Video "Un-Boxing" Review of the same said tool kit:

And for the sake of anyone thinking about doing this...Eric the Car Guy has a nice review:

Using a FEW drops of 3&1 Oil will do the trick... But inducing too much oil in there will cause the engine to hydro-lock once the plugs are re-installed and the engine is cranked over and may risk damaging or bending connecting rods. And so... "Lightly Oiling on the Wet Test... is Best!"

 

[littleblazer]

If you do a compression test, I suggest partially fogging the motor. That way you don't have to worry about adding too much or little oil. Just do it down the brake booster.

Personally a healthy motor should test fine dry as well. I'd be looking for one that is significantly lower or flutters more.

 

[mrrsm]

If you do a compression test, I suggest partially fogging the motor. That way you don't have to worry about adding too much or little oil. Just do it down the brake booster.

Personally a healthy motor should test fine dry as well. I'd be looking for one that is significantly lower or flutters more.

Not to HJ this Thread... But I would be very interested in learning how to do this "Fogging" procedure... so if you have a previous post on the subject and can drop a link here..it would be great. Or perhaps you could create a new one over in the Technical Discussion area. I can guarantee... many people will appreciate knowing how to do this.

 

[littleblazer]

Not to HJ this Thread... But I would be very interested in learning how to do this "Fogging" procedure... so if you have a previously post on the subject and can drop a link here..it would be great. Or perhaps you could create a new one over in the Technical Discussion area. I can guarantee... many people will appreciate knowing how to do this.

Fogging on a carburetor is simply pouring a light oil down the intake while it's running. Producing a light oil coating to prevent rust build up for long periods of lay up. On the i6 I would go via the brake booster like you would to do a seafoam treatment. I use marvel on the boat poured in very slowly until you start to see smoke from the exhaust. Once you get that smoke let it run for a few seconds without adding your oil of choice and kill the ignition. Not enough in there to hydrolock anything so it should be enough for a wet test.
About 5 minutes in here, except you would go down the vacuum line. A seafoam treatment is basically fogging a motor. And you probably won't need to use as much as he did either. (It's a boat but the same principal...)

 

[mrrsm]

This is a PERFECT Explanation and Reply! Thanks...