4.2 timing chain

jener

Original poster
Member
Jan 11, 2016
13
mt
I've got an 08 envoy with a 4.2 and a bad timing chain. It's only got 65000 miles on it. I'm going to put a new timing chain on it. I know this is a horrible thing to tackle. My question is, would there be any benefit to pulling the engine to replace it?
Any advice is appreciated
 

jener

Original poster
Member
Jan 11, 2016
13
mt
It runs horrible.A dealer ran the codes and said the guides were out. Then I was doing research and figured out I put the wrong weight of oil in it
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Chain is highly unlikely. They don't break or really wear out. I had to replace the chain tensioner because the chain was loose and hitting the top guide. Using the wrong oil would not do anything to the chain or guides. Might (and that's a very big MIGHT) affect the cam phaser but are not very affected by oil viscosity unless you something really thick like 50 weight racing oil.

Please provide the codes. We can better help advise you then. I have a feeling the stealership was trying to fleece you for a very expensive unnecessary job.
 
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jener

Original poster
Member
Jan 11, 2016
13
mt
Ok, I'll see if I 'm get them. The dealer told me the guides were gone. I haven't driven it in months, so I don't exactly remember what it was doing. I do know it is leaking oil like mad, from somewhere up front.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Unless he took off the valve cover, there is no way to know that. But a major oil leak is unusual for this engine. Was it leaking before you brought it to the dealer? That could be something as simple as a loose oil filter.

Again, it's extremely unusual for the chain guides to be gone at that mileage and definitely would not be caused by oil. An oil analysis could confirm that as there would be huge amounts of aluminum in the oil from the chain rubbing on the chain guide bases if the nylon inserts fell off. I have never heard of these just falling off and they usually last the life the vehicle, some 200k+ miles
 
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gmcman

Member
Dec 12, 2011
4,656
OP, not to call your dealer a liar, but what others have said, I want to say it's something else as well. I would try some 5W-30 synthetic substituting 1 qt of marvel mystery oil...keep in mind these take 7 qts.

Let us know where the leak is.
 
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jener

Original poster
Member
Jan 11, 2016
13
mt
I finally the envoy down to pull codes. The only code was poo17. It said crank position sensor, cam correlation sensor bank one?
I found the oil leak , it is on the passenger side on the rear of the engine under the exhaust manifold. I couldn't see the actual leak, but I could see it squirting oil on the exhaust at the flange.
It is very hard to start, and idles rough at a low rpm, it is very low on power
Thanks for any help
Jene
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Could be a bad crank sensor, which would explain the engine running poorly. I'd definitely try that before even thinking of touching the timing chain. Keep in mind that if you do replace it, you will need a CASE relearn. I'd also replace the cam sensor just to be sure. Both are fairly cheap.
 

jener

Original poster
Member
Jan 11, 2016
13
mt
What is a case relearn? How difficult are they to replace?
Thank you

How about the oil leak?
 
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Mooseman

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Dec 4, 2011
25,262
Ottawa, ON
CASE: Crankshaft Angle SEnsor
It can only be done by either a dealer or a shop with a high end scanner.

The oil leak I have no clue where that could be from. Squirting onto the exhaust flange? I'm thinking it's the transmission oil cooler line. Did you look at the colour of the oil? I'd also not drive it as the oil could catch fire (it has happened in the past).
 

jener

Original poster
Member
Jan 11, 2016
13
mt
The oil appears to be engine oil. It is parked!
Would it be worthwhile to check the cam actuator? Or just go straight to the crank and cam sensors?
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Start with the easier parts first as the cam actuator (or phaser) is a more involved repair and the part is also more expensive. Also check the operation or replace the CPAS (solenoid) located just behind the power steering pump on the head. That one though usually throws a P0014 code. The phaser and solenoid can be checked by the dealer using a Tech 2 scanner.

But you gotta find that oil leak first. Is it possible that it's leaking from the CPAS? I can't think where else but there and the oil filter where it could be squirting under pressure.
 

Sparky

Member
Dec 4, 2011
12,927
Can you grab a pic of where the oil is leaking at?
 

jener

Original poster
Member
Jan 11, 2016
13
mt
The oil is on the passenger side, on the back under the exhaust manifold. It is engine oil. Is there anything in that area? It isn't related to the way it runs, I don't believe. It started leaking after it started running like crap
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
I wonder if there may be an oil gallery plug there or something similar near that area that may have sprung a leak. I'd take to an independent mechanic you trust and see if he can find that leak lifted on a hoist.

It could be possible that if oil [pressure is being lost, it may affect the VVT system and cause wrong camshaft timing.
 

Sparky

Member
Dec 4, 2011
12,927
The only thing back there that I can think of is the pan gasket, but there shouldn't be any pressure to make it spray out :blinkhuh:
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
It would have a long way to spray back there. Best thing is still to get it up on a hoist and have a good look.
 

jener

Original poster
Member
Jan 11, 2016
13
mt
Well we got the oil leak figured out. There's a big fucking hole in the block between 2 oil plugs underneath the exhaust manifold.
Sad day
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Very sad. First time I've heard of something like that. So this makes the timing chain issue a moot point, which the dealer should have picked up on.

Will you get the engine replaced? A quick look on car-part.com, there are a few sub 100k mile engines in the $1200 range.
 

jener

Original poster
Member
Jan 11, 2016
13
mt
I have a buddy who works at a wrecking yard. He thinks he can get one for 850.
The little bit of looking I've done, it looks like 07 and 08 are different. Is that right? Right now I'm kind of trying to figure out what to do. I do thank you for all your help.
 

Sparky

Member
Dec 4, 2011
12,927
Probably runs bad not because of the timing chain or any of that, but because the hole was likely caused by some part of the engine (like a connecting rod) getting launched through the block.

Holes don't happen in engine blocks without something catastrophic happening.
 

jener

Original poster
Member
Jan 11, 2016
13
mt
It was running had long before it started leaking oil. Thats what weird, it still runs good oil pressure.
 

Sparky

Member
Dec 4, 2011
12,927
JB weld!
 

Capote

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Jul 14, 2014
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That's freaking crazy man
 

rider19r

Member
Aug 2, 2023
3
ukiah ca 95482
i would like to know if anyone has accidently dropped the timing chain from the lower gear and had any luck getting it back on lower gear w/o pulling the front cover ! is it even possible, because my attemted cam phaser replacement in the street outside my buddys home has me up against a tow away if we get caught taking the pan off this thing ! is it possible to get the chain back on the lower gear.....it came off the gear pretty easily didnt even know it ! ???
 

mrrsm

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Oct 22, 2015
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Because of the presence of the Gerotor Oil Pump directly surrounding that area and the lack of space, along with the position of the *DOT* on the Face of the Crankshaft Cog-Gear when the #1 Piston sits at TDC ...without removing the Front Timing Cover entirely... you would just be taking a "Shot In The Dark" for such an unfortunate event. Have you got any other friends who would help you by letting you tow it over to THEIR Yard to finish this Epic Job?

GM42LTIMINGCHAIN.jpg


You can see from these images just how *congested* the interior-obstructive objects in that area really are down inside there:

49571443736_2e402a3483_z.jpg49571444416_3dfaa58f17_c.jpg

49571444361_732893bbcf_c.jpg49571671957_2a62a1016f_c.jpg
 

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Mooseman

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Dec 4, 2011
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Ottawa, ON
Yeah, like @mrrsm said. No way to know if the chain link is properly lined up to the dot. If it's off, at the very least it will run like poop, and at worse, destroy your engine with valve to piston contact. Unfortunately, your pan and timing cover has to come off.
 
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mrrsm

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...and just to Make Damned Sure... After I saw my own images ...I spied the ONE THING that just might mean there could possibly be a way out of this Timing Chain Purgatory after seeing THIS Feature in the Lower, Inner Timing Cover-Gerotor Oil Pump Casement. Notice how Deep that Protective Aluminum Cast Investment Well or Shroud is down inside there...?

GMTIMINGCOVER1.jpg

Well... I thought MAYBE... Just MAYBE.. that once the Crankshaft Cog-Sprocket was slid over the Nose of the Crankshaft (#1 Cylinder TDC TIMING PIN - Quasi-Woodruff Key Locater) and then inserted back through the Center Gerotor Female Cog Port... WITH the New Timing Chain installed...that MAYBE it might be IMPOSSIBLE for THAT section of the Chain Links to completely Fall or Drop Off the Sprocket Teeth once FREE... and Just MAYBE ...it would wind up being Snug Enough in there to prevent that unfortunate event from ever happening.

So I decided to spring for an inexpensive "MOCA" Timing Chain Set Kit (for around Sixty Two Bucks) just so I could try out THIS Experiment (Which... AFAIK... had not as yet been done... to my certain knowledge) and then be able to SEE First Hand if there was ANY HOPE that this might WORK. But, Sadly... NOPE.

The New Crankshaft Cog was VERY SNUG... so it was NOT necessary to have the Nose of the Crankshaft poking through there for the sake of Stability. The Chain Links also fit VERY SNUG.... and even though there was Not a LOT of Extra Space once the Chain became LOOSE... it could still manage to Slip completely OFF of the Sprocket Teeth and then slide either to the Left or slide to the Right by One Tooth ...or even MORE... WITH EASE.

Now, If ONLY GM had designed a Black Plastic "UFC Mouth Guard" sort of device tucked inside of that narrow space down inside there to Prevent that Chain from Dropping Down from those Teeth by even a 'little bit'... then having such a purpose-made "Thing" fixed in place down there would have made HUGE difference in expediting this Cam-Phaser Repair while working from the Top - Down... with the added "Peace Of Mind" that once the Tensioner was Re-Compressed and the Two Timing Marks were aligned on the Exhaust Camshaft Cam-Phaser Sprocket and the Intake Camshaft Sprocket, everything would work properly.


GMTIMINGCOVER1.jpgGMTIMINGCOVER2.jpg
GMTIMINGCOVER4.jpgGMTIMINGCOVER5.jpgGMTIMINGCOVER7.jpg

Anyhow... the one other thing worth mentioning though is that for the Money... this Off Brand "MOCA" Timing Chain Set was of a MUCH Higher Quality than I expected it would ever be. For example, consider that the Top Chain Guide was not only stamped from Thicker, Good Quality Mild Steel... but they Chrome Plated the Damned Thing, too ... and... they also installed a THICKER Black Plastic Chain Guide Plate Insert as well!

Take a look at the image of the Timing Chain Tensioner Cast Iron Body and you can see that it was Cast FIRST and Then Machined down very nicely afterwards. Every Component that was necessary (Including the Special High Temp Silicone Sealant) was present inside of this kit; individually Labeled, Lightly Lubricated, bagged up hermetically and finally, sealed inside of a Larger Bag with the "MOCA" Company Logo embossed as a "Point of Pride" Motif.

So if I was working on any GM 4.2L LL8 Engine as a "Budget Build"... I might just consider getting THIS Kit instead of my usual choice of only using the more expensive Cloyes After-Market Repair Products. ...Just sayin'... Anyways... I was trying to Look Out For You, Dude... But this Idea was a BUST... Sorry about that... :>(

MOCA Auto Parts DOES Carry Quite A Few Things... for the Owners of Our GMT360s:


61rHbLuWQJL._AC_SL1000_.jpg51sVxk6VkhL._AC_SL1000_.jpg51p0qMx2MpL._AC_SL1000_.jpg51Jty-js-yL._AC_SL1000_.jpg51cRMmk14kL._AC_SL1001_.jpg



https://shop.mocaautoparts.com/?shpxid=b394bdf0-fb56-4e0d-bce4-2f00534855ec

MOCATIMINGSET1.jpgMOCATIMINGSET2.jpgMOCATIMINGSET3.jpgMOCATIMINGSET4.jpg
 
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