The other day I just crested over 220k miles and heard a small knock when on the highway. Parked it at home and have yet to start tearing into anything. I'm pretty good at most repairs on vehicles just unsure if this will result in the engine having to be pulled. Any help would be greatly appreciated. Oil has been maintained and filter changed everytime, with a quart or two normally missing at the cycle change.
Dreaded Knocking Noise 2008 GMC Envoy 4.2L I6 220k miles
- Thread starter Furious92
- Start date
Welcome to GMT Nation...
(1) First... Start with making a Video closer to the underside area between the Back of the Engine Block and the Bell Housing of the Transmission. That Rhythmic "1,2,3,4....1,2,3,4" sounds more like a problem with a Cracked Flex Plate versus Rod Knock and it is fairly easy to investigate this area first then Post your Follow Up Video back here whenever convenient.
(2) Next... Perform a Dry and Wet Compression Test after pulling the Spark Plugs and looking them all over very carefully for anything other than a "Fried Chicken Brown" patina inside. Jot down their results for Dry first and Wet Second and let us have a look at the results.
Other Hints from Better Minds @ GMTN should follow along...
Glad you came here for Help...
(1) First... Start with making a Video closer to the underside area between the Back of the Engine Block and the Bell Housing of the Transmission. That Rhythmic "1,2,3,4....1,2,3,4" sounds more like a problem with a Cracked Flex Plate versus Rod Knock and it is fairly easy to investigate this area first then Post your Follow Up Video back here whenever convenient.
(2) Next... Perform a Dry and Wet Compression Test after pulling the Spark Plugs and looking them all over very carefully for anything other than a "Fried Chicken Brown" patina inside. Jot down their results for Dry first and Wet Second and let us have a look at the results.
Other Hints from Better Minds @ GMTN should follow along...
Glad you came here for Help...
Glad to be here. You guys know your stuff! I have a 2nd video more from the backside near the transmission and rear of the engine. I will definitely do the test, I can get the tester kit from the parts store tomorrow after work. I know the truck isn't much to some but I love this thing and would like to keep it going. Tomorrow I can also remove the plastic shroud and get it on ramps to get a better video as well.
Mooseman
Moderator
That really sounds like rod knock. A couple of things you can do to confirm. Drain the oil and look for metal, either glitter or metal pieces. Either spells death for that engine. Next, to confirm it futher, you could use this method to find which cylinder.
When you rev the engine, does the noise stay constant but at a faster speed? Although a broken flexplate is possible, the noise is usually irregular and tinny, especially when it's revved.
When you rev the engine, does the noise stay constant but at a faster speed? Although a broken flexplate is possible, the noise is usually irregular and tinny, especially when it's revved.
THAT is Great "Text Book" Follow Up Video...
Prior to performing the Dry & Wet Compression Testing... Make certain to use either "Canned" Air or Compressed Air to vacate and expel any accumulated Rain Water (or Motor Oil) that may have leaked down into the Spark Plug Wells from the Valve Cover Gaskets prior to unwinding the Spark Plugs from an ICE COLD Engine Block.
By the way...I can see from having spotted your K&N Oil Filter during your filming of the 2nd Video that you have been taking your Motor Oil and Filter Changes...Seriously for your Very High Mileage LL8 Motor. So THAT is Way Cool...Dude.
One observation... in the case of a Bad Connecting Rod...whenever the Engine accelerates to a Higher RPM ...the Knocking Noise tends to subside. Nonetheless, I'm keeping an open mind and await the results of your Compression Test, just in case @Mooseman 's 'ear' for this instance is better than my initial impression of it being the Flex-Plate misbehaving.
That Last Video he has recommended is the BEST Technique around to follow for isolating a Sloppy Con-Rod.
Prior to performing the Dry & Wet Compression Testing... Make certain to use either "Canned" Air or Compressed Air to vacate and expel any accumulated Rain Water (or Motor Oil) that may have leaked down into the Spark Plug Wells from the Valve Cover Gaskets prior to unwinding the Spark Plugs from an ICE COLD Engine Block.
By the way...I can see from having spotted your K&N Oil Filter during your filming of the 2nd Video that you have been taking your Motor Oil and Filter Changes...Seriously for your Very High Mileage LL8 Motor. So THAT is Way Cool...Dude.
One observation... in the case of a Bad Connecting Rod...whenever the Engine accelerates to a Higher RPM ...the Knocking Noise tends to subside. Nonetheless, I'm keeping an open mind and await the results of your Compression Test, just in case @Mooseman 's 'ear' for this instance is better than my initial impression of it being the Flex-Plate misbehaving.
That Last Video he has recommended is the BEST Technique around to follow for isolating a Sloppy Con-Rod.
Last edited:
Will do. I have been running the K&N ever since I gained ownership of the vehicle and tried to always get the best high mileage oil I could depending on the availability at the time. Will drain the oil though tomorrow and look and see if there is any metal/glitter shards and check back in with you all. Thanks again!
Check exhaust manifold for leaks. Do the simple stuff first. The first video sounded like rod knock, second more like exhaust leak. But it is hard to go just by a video.
Just to keep everyone up to date: This morning before work I went out to the truck to move it so I can drive my other car until I get this repaired. Car was on for maybe a total of 5 minutes. Idle was rough and seemed like it wanted to stall. Died right as I went to park it, check engine light came on and has codes P0014 and P0017. EDIT: To add I also tried starting the car last night without the belt on to check if the knock stayed and it did... not sure if that could have set the codes off. Have yet to look at connectors for leaks but plan to do so when I'm off work at 4pm. Don't know if that would cause the knock to begin with or if the codes were thrown because of the knocking happening. Just figured I would update, racking my brain out over this all night lol.
Last edited:
Mooseman
Moderator
No. These are codes for the VVT system. This usually points to an issue with the VVT actuator or the cam phaser. It is possible that the actuator is jammed because of metal contamination. It usually does not prevent the engine from starting or running unless it is severely over advanced.
Also... If the Flex-Plate has been cracking around the Crankshaft End Bolt-On Flange, it could be due to the Crankshaft hunting in and out <--> after the Thrust Bearings meant to restrict this Fore and Aft movements and impede any such excessive motions have failed.
The Thrust Bearing Plates for the LL8 Engine are NOT really 'Solid State" in their Design (see the attached image) and once they wear down substantially, they can fall out or disintegrate and thoroughly contaminate the Oil Galleries and other internal areas deep inside of the Engine:
The result is that the Crankshaft will "Hunt" forwards and backwards enough to trigger a P0017 "Crankshaft-Camshaft" Correlation Code once the Reluctor Wheel Cut-Outs lose their reference in relation to their rotational proximity to the in-dwelling nose of the CKP (Crankshaft Position Sensor).
These events happening so close aboard each other means that Changing and Examining your Oil for signs of Non-Ferrous Metal Particles Contamination as well as performing an Autopsy on the Fan-Folded Inner Filter Paper of that K&N Oil Filter will become very important to investigate when washed out in a Bucket using some Kerosene with a Stiff Parts Brush under the glare of a Bright Light.
Please note that if the Crankshaft becomes completely unrestricted in moving longitudinally inside of the Engine Block, as it rotates around, it might be possible for the Crankshaft Counter-Weights to Strike the Sides of the Mains Bustresses and be the source of all this "Racket" as well. This might also explain why you may not hear that sound all of the time. The Motor MUST have those Thrust Plates situated in place near the #5-#6 Mains position inside of the Engine acting as "Guides" to make the Crankshaft behave itself when under the stress of Rising & Falling RPM and Torque.
The Thrust Bearing Plates for the LL8 Engine are NOT really 'Solid State" in their Design (see the attached image) and once they wear down substantially, they can fall out or disintegrate and thoroughly contaminate the Oil Galleries and other internal areas deep inside of the Engine:
The result is that the Crankshaft will "Hunt" forwards and backwards enough to trigger a P0017 "Crankshaft-Camshaft" Correlation Code once the Reluctor Wheel Cut-Outs lose their reference in relation to their rotational proximity to the in-dwelling nose of the CKP (Crankshaft Position Sensor).
These events happening so close aboard each other means that Changing and Examining your Oil for signs of Non-Ferrous Metal Particles Contamination as well as performing an Autopsy on the Fan-Folded Inner Filter Paper of that K&N Oil Filter will become very important to investigate when washed out in a Bucket using some Kerosene with a Stiff Parts Brush under the glare of a Bright Light.
Please note that if the Crankshaft becomes completely unrestricted in moving longitudinally inside of the Engine Block, as it rotates around, it might be possible for the Crankshaft Counter-Weights to Strike the Sides of the Mains Bustresses and be the source of all this "Racket" as well. This might also explain why you may not hear that sound all of the time. The Motor MUST have those Thrust Plates situated in place near the #5-#6 Mains position inside of the Engine acting as "Guides" to make the Crankshaft behave itself when under the stress of Rising & Falling RPM and Torque.
Last edited:
aaserv
Member
I know the truck isn't much to some ....... Id get these people out of my life THEN start to working on the motor.....
Mooseman
Moderator
aaserv
Member
Mooseman
Moderator
So I assume people in his life saying... OK, a bit drastic, but OK. Working through it to confirm suspicions first and we'll go from there.
Given the developments, I'm also of the opinion of a rod bearing going away. If that's the case, I'd not waste time doing a compression test. All pistons will still be going up and down, making relative compression. A cylinder with a bad bearing may not have sufficiently reduced pressure to be identified with certainty.
If you don't want to drain the oil, I'd go straight to pulling the PS pump to access and remove the VVT valve for inspection of contaminants on the filter screen. That may be your best, fastest, easiest method for confirming evidence of a bearing failure. That investigation can be followed by removal of the spark plugs and performing the screw driver test on the piston tops, as demonstrated in the video posted above.
Rick
If you don't want to drain the oil, I'd go straight to pulling the PS pump to access and remove the VVT valve for inspection of contaminants on the filter screen. That may be your best, fastest, easiest method for confirming evidence of a bearing failure. That investigation can be followed by removal of the spark plugs and performing the screw driver test on the piston tops, as demonstrated in the video posted above.
Rick
Sorry for the late reply, with work and other things I've been kept busy. I went ahead and drained the oil tonight and noticed a glitter like metal in the oil at the end. I suppose with 220k+ miles anything was bound to happen at this point, regardless of my oil changing habits lol. So I'm assuming the rod bearing like you've all helped diagnose
. Appreciate all you guys have done! Now to figure out what's going to be worth while to do, just had new suspension all the way around, tires, brakes/rotors, wheel hubs, probably about $2000 or more in the past year put on it. Don't want to scrap it, but I feel like with this many miles unless I were to pull the engine and rebuild it, I might be chasing other problems with it in the future.
. Appreciate all you guys have done! Now to figure out what's going to be worth while to do, just had new suspension all the way around, tires, brakes/rotors, wheel hubs, probably about $2000 or more in the past year put on it. Don't want to scrap it, but I feel like with this many miles unless I were to pull the engine and rebuild it, I might be chasing other problems with it in the future.Mines doing the same thing at startup. Always had a bit of piston slap that went away in a few seconds since I bought it in 2008 on a cold start (it's a 2004 TB LS). The oils been changed every 3-4 thousand miles since I bought it.
Recently I've been getting a slight rap on starts, intermittently. Once you hear a rod/crank knock there's no denying it.
What's killing me is it's intermittent on startup, revving the engine does nothing for the noise to make it worse.
Drove it to Maryland and back yesterday, no noises.
So, much like you, I'm changing the oil this week and looking for the metallic sheen, crossing my fingers there isn't any.
Mooseman
Moderator
That's the dilemma I had with two of mine, the '02 4.2 TB and the '06 5.3 Saab. The TB blew the trans at 330k km but the body was too far gone so not worth it to fix and the motor had been a trouble child having been poorly maintained during its life in the previous truck it came from. The Saab, although I liked this truck a lot, was a bag of trouble since I got it and it got a rod knock after having, what I thought, was piston slap the whole time I had it. It never had any glitter in the oil before that. The body was also too far gone with rust and the trans was also original with 220k km. Both were just not worth the time, money or effort to rescue.
You'll have to evaluate for yourself what this truck is worth to you and if it's worth it to throw another $2000-3000 at it. The next big thing that might go is the trans so keep that in mind. The body is the biggest factor in my eyes. Being in the rust belt, that is the biggest factor. If the body has rust through or the frame is getting eaten away, that would be a killer right there for me.
You'll have to evaluate for yourself what this truck is worth to you and if it's worth it to throw another $2000-3000 at it. The next big thing that might go is the trans so keep that in mind. The body is the biggest factor in my eyes. Being in the rust belt, that is the biggest factor. If the body has rust through or the frame is getting eaten away, that would be a killer right there for me.
How is the interior/exterior? If the rest of the vehicle is serviceable for say, another 5 years, then why not make it go again with either a rebuild or replacement engine?
If you just don't want to see the truck on your driveway any longer, I understand. Using strictly an economic outlook, you can make the case for replacing the engine vs getting another used car and other potential issues.
Rick
Update again: Currently I'm in the process of finding another vehicle for the time being, but going to keep the Envoy and next spring get a motor and put it in. Lol I just love that truck. Anyways I was looking at a 2005 Buick Rainier CXL, https://gmtnation.com/forums/threads/2005-buick-rainier-cxl-looking-to-buy-what-to-look-for.22484/
And was wondering if anyone here could chime in on things for me to check/look at it. Thanks guys!
And was wondering if anyone here could chime in on things for me to check/look at it. Thanks guys!