Life expectancy of timing chain, guides, and tensioner?

c good

Original poster
Member
Dec 8, 2011
526
Since I believe I have worked the gremlins out of my Envoy (new coil, and Berryman's soak) I"m enjoying driving it again. I'm almost at 190K miles. When should I start thinking about replacing timing chain, guides, and tensioner? I know this can be service dependent but this vehicle has been well maintained by me and the previous owner. All fluids on time or earlier. That includes, engine oil, transmission fluid (Dex VI) and filter, Transfer case (auto track II) front differential (mobil 1 full synthetic), rear differential (mobil one full synthetic), radiator coolant (gm dex cool), power steering fluid, and brake fluid.
 
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mrrsm

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Oct 22, 2015
7,642
Tampa Bay Area
Technically, the recent Nominal Engine Performance improvements you've experienced might be compared with something akin to a 50 Year Old Life-Long Smoker taking up Jogging and after finding he has lost a legitimate (10) pounds from his recent, fresh weekly exertions... imagines that he has cured himself of all prior ills.

The formerly Badly Clogged Up Screen on the Oil Pump Pick Up Tube might be showing signs of improvement... but the events leading up to that Rash of "Low Oil Pressure" Alert Dash Lights you encountered was an indicator that if there is any damage lurking inside that LL8 Engine Block... it has long since happened and that a few Very Bad Things may still be lurking in the background waiting to raise their Ugly Heads.

As for the Timing Chain R&R, the Biggest Issues with High Mileage, Semi-Clogged Engines are the 'Big Three Codes' popping up; either all or singly as follows:

P0017
P0014
P1345

All of which will focus the Owner's attention on problems involving Crankshaft and Camshaft Correlation.

Poor Oiling of the Hydraulically Fed Tension Plunger inside of the Timing Chain Tensioner along with the out-and-out wearing down of the Two Timing Chain Plastic-Nylon Guides along with inevitable Chain Wear and Stretch will invite the Crankshaft to Camshaft Correlation (Ignition Timing) Nightmare.

These events WILL require following the well documented actions of performing the R&R of the Crankcase-Oil-Pan, the Front Timing Cover and the Valve Cover to do this entire Cloyes Timing Chain Set R&R.

Performing this work "in-situ" is worse than just Pulling the Motor and doing ALL of what is required after the LL8 becomes completely accessible once Mounted on an Engine Stand. @Mooseman has often recommended obtaining a Well-Tempered, Low Mileage GM 4.2L Motor and then conducting an Engine Swap in lieu of doing the "In House" Timing Chain Repair as a MUCH Better Course of Action to Follow. I concur with this approach.

The Smart Man in this scenario... First Mounts the "Swap Motor" on an Engine Stand and performs the Cloyes Timing Chain Set R&R and De-Mung and De-Carbon Efforts to Clean the Bottom End of any Black Carbon Build Up from the innards (Oil Pick Up Tube Screen) as well... in a Pre-Emptive Strike to ensure that the "New" Motor is being given every single chance to behave itself once it's installed and is Up & Running.
 
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mrrsm

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Oct 22, 2015
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To these, I would add in even more things to attend to WHILE THE MOTOR IS STILL ON THE ENGINE STAND:

(1) Pull the Spark Plugs and using the FOAMING version of ACDelco TEC (Top Engine Cleaner)... FILL ALL (6) Cylinders to the BRIM and then INVERT the Engine to Drain Out The Black Carbon Mung (3) Hours Later.

(2) Check the Torque on the Fasteners holding the Gerotor Oil Pump to the Oiling Cavity on the Front Timing Cover and also REPLACE the Blue Teflon "O" Ring in between the Oil Pick Up Tube and the Oil Pump.

(3)Inspect and Replace the Flex-Plate if there are the slightest signs of any Cracking or Fractures around the Crankshaft Holding Flange and Fasteners.

(4) Replace the Three Figure 8 "O"Ring Style Gaskets on the Intake Manifold along with ALL of the similar style Gaskets on the Valve Cover. Inspect the Valve Train for Roller Camshaft Follower Lobe Galling and replace the Roller Rockers as needed.

(5) R&R the CPAS and Clean the Screens looking for THIS exact problem as found by Paul "Scanner" Danner's Brother:


(6) Install the Starter BEFORE Installing the Engine while it is still EZR to do so... ON THE STAND.

(7) Inspect and Replace the Old, Cracked, Leaking Exhaust Manifold while access to performing Broken Bolt Repairs is EZR to do with the Engine mounted ON THE STAND.
 
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Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
The timing system is quite durable for the life of the engine and the vast majority are never opened up. My situation was quite different. It was a replacement engine that, unbeknownst to me, was poorly maintained as evidenced by the amount of coked up oil inside once I opened it. It developed several issues with the timing system including failure of the chain tensioner and the cam phaser (twice). The process is well documented in the FAQ. However, I do not recommend taking the engine out completely for this. That's what we actually recommend for the cylinder head. Although replacing the timing chain parts is quite laborious, it's not quite as bad as yanking the engine out.

I wouldn't worry about it until something does fail. Drive and enjoy.
 
Dec 5, 2011
574
Central Pennsylvania
I have approximately 280k miles on the original engine, trans, tcase, and diffs with nothing but fluid, filter, gasket, coil, plug, and belt changes with the exception of the exhaust manifold and O2 sensor. I still drive this thing like I stole it ten minutes ago....
 

rchalmers3

Member
Jul 11, 2020
207
Irmo, SC
I''l second Tequila Warrior's experience. I have now seen a half dozen of these engines up close and personal, all with high (160k-280k) on the clock.

Half of the engines I have opened were ruined due to rod bearing seizures and the subsequent parting of the reciprocating/rotating pieces. None of them suffered from extreme chain, sprocket or guide wear. Besides some severe coking deposits on the parts, I found only one engine had chain guide plastic that was somewhat brittle, but I guess would have continued to serve had I not opened it and dropped the guides on the floor!

Rick
 

Ilikemy3s

Member
Dec 3, 2011
367
I have 233K+ miles on mine and I am hooping to make it to 300K Been using Mobile 1 oil and filter since I bought it 6 years ago with 86K on it. Along with other regular (if not over maintainence) and tune ups, mostly highway mileage, and not beating on it, I am keeping my fingers crossed
 

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