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Discussion Starter #1
In a different topic which I successfully (but unintentionally derailed) I started talking about an engine job that came into our shop a couple of days ago.



https://www.coloradofans.com/forums/73-new-member-introductions/409447-new-owner-2005-canyon-2-8l.html#post5207771 TL:DR


Anyways, to bring everyone up to speed, since I rarely do much diagnostic work due to my position in our Union and my lack of training, they usually give me a lot of the engine jobs, since its just nuts and bolts and something I dont have to plug a scanner in to. :surprise:0:)



One of our ESU Tahoes, with 62K miles broke down at LaGuardia Airport. They diagnosed it as having zero compression in all 8 cylinders and had it towed to my shop, where we do most of the long term work. Mind you, there was not a single code stored in the OBD. Im sure many of us have seen 1 or 2 cylinders lose compression, or low compression in a couple cylinders but..... ALL of them on a V-8??????



Upon going out to the lot to hopefully limp it into the shop, sure as hell, it was spinning over as if all 8 spark plugs were removed. After looking under the hood and verifying they were in fact still in the block, we pushed it in.



Since it was already determined it was getting a new engine, I ordered all the new goodies and set about taking the engine out.



Being a mechanic for roughly 40 years, Ive seen more than my fair share of blown head gaskets, hand grenaded blocks and everything in between.....but never have I seen or heard of a V-8 loosing compression in all 8 cylinders.



After taking the engine out and finding out I wont get a new engine till tomorrow or Monday, I figured, hell, I want to see what the hell went wrong. Mind you, no one else in my shop ever heard of this, and a search from GOOGLE didnt show it as an issue anywhere either.



I have to add......turning the engine over by hand, there was no resistance such as something mechanical being broken, such as a rod etc. (we have done more than one where we had to take the torque converter with the block due to massive internal destruction where we couldnt turn the crank to get to the TC bolts) We took off the center valley cover and turned the engine over....you could see the cam and timing chain moving, and saw the valves going up and down.

Hmmmmmmmm..........


I decided to take the heads off and well..... the damage was quite clear. You can clearly see the impact of the intake valves on all 8 cylinders. Plus.....well, wait till you see the push rods.



Of the 8 intake valves, you could almost fit your pinky into 3 of the openings, with no rocker arms on......clearly it bent every one of them.



So, what the hell caused such damage. After taking the timing cover off, the timing chain was clearly nice and tight, the guides were still intact. So I decided to take the VVT mechanism off and saw the problem immediately and promptly laughed my ass off......... a .29 cent dowel snapped off the cam. Plain and simple. For the life of me, I cant see how the hell this could have happened but in fact, the proof is there.



So, now if you ever hear someone say 'have you ever heard of a V-8 that lost compression in all 8 cylinders" you'll get to say, 'Hell yea......check your cam gear dowel" :rofl:rofl:rofl


Pushrods



Impact points from the intake valves








Look MA, no rocker arm connected -




Cam shaft with half the dowel pin -





VVT mechanism with other half of dowel pin
 

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hahaha thats funny.... well at least if was diagnosed correctly---needs new engine... cuz thats fuc*ed up... lol
 

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I wish I could have verified oil pressure or lack there of, as Im curious if that was the main culprit.

We have many engines in the 6000-7000 hour range (as many of our vehicles idle 23 hours a day) and of all the engines Ive done, the ones with catastrophic damage are usually the result of no oil or no oil pressure.

We only use Mobil 1 but sadly, our fleet doesnt get PMed like it should.
 

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Well worth the time spent on the tear down. Thanks for sharing.
 

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It kind of looks like heat may have fatigued the pin. What year is the truck? I believe hearing my son say that he read a lot of problems on the GM Truck forums about the 5.3L engines having problems with failed lifters. He has a 2015 model, so he studies that a lot. Has read a lot about trashed out motors due to the AFM, and cylinder deactivation.
 

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Looks like on one of the cylinders, a valve contacted the top of the piston. Probably the same company that made that pin, made the wrist pins in the 2.8L,
 

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It kind of looks like heat may have fatigued the pin. What year is the truck? I believe hearing my son say that he read a lot of problems on the GM Truck forums about the 5.3L engines having problems with failed lifters. He has a 2015 model, so he studies that a lot. Has read a lot about trashed out motors due to the AFM, and cylinder deactivation.
Failed afm lifters is a very common problem. Most deactivate the afm or delete it all together
 

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Discussion Starter #11
Looks like on one of the cylinders, a valve contacted the top of the piston. Probably the same company that made that pin, made the wrist pins in the 2.8L,
Oh no, my friend, EVERY intake hit every piston. My picture-taking skills suck but in person, you could clearly see the impact points of each valve. 4 intakes were stuck from 1/8 to 1/4 of an inch with no rocker arms connected, the other 4 were closed with only light impact marks but, they were clearly visible.

I just need to get a better camera. :rofl:rofl:rofl:rofl
 
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