L9H Engine Failure - What to do now? HELP

[L9H 2 LM2]

Hello all, first timer here. This may be a little lengthy but please bare with me.

 

Let me start by saying I am by no means a ace mechanic. But I have worked on boats and in construction most of my life (and I did stay at a holiday end express last night) so by default I do have a general of knowledge of engines but no more than any other hard working blue collar American.

 

I have a 09 GMC Sierra 1500 Denali (L9H) with 120k. A few days ago I was driving down the highway and I heard a strange sound (tapping) in the engine for about 10 seconds followed by a light shutter then it cleared up and the truck drove like normal for the remainder of the 5 min trip. I got back in the truck the next day and drove back home with no problems or weird sounds. About 10 to 15 min after getting home I jumped back in the truck and when I cranked the truck up it started making a VERY loud knocking noise that could be heard over the engine. I immediately turned it off and my heart sunk. I towed it into my shed and took the valve covers and intake manifold off and checked all of the rocker arms, push rods, tops of the valves and looked at the cam through the top of the block while turning the engine over to make sure it wasn't broke in half. From what I could see everything looked straight and tight. So I put it back together and brought it to a trusted mechanic (which is a friend if mine) and after putting it up on the lift he called with the worse news i could have imagined... he said he did not do a compression test or pull the oil pan but by listening to the engine while running and then seeing white smoke in the exhaust he concluded it to be a broken rod.

 

Now obviously I will need to do a compression test and leak down test to confirm this but after hearing that sound, unfortunately, I don't think hes far off on his diagnosis.

 

Has anyone ever heard of this or similar problems with these engines? It just blows my mind that I quite possibly have catastrophic engine failure in a perfectly stock and well maintained vehicle.

 

These motors are not cheap and to make matters worse, from what I have researched the past few days, I dont think you can just go buy a reman stock short/long block for the L9H. Only options I have found so far (locally and on the net) are either brand new complete engines for around $6-$8k, a bare block (which I would then have to fully rebuild or pay someone to do it) or a used (salvaged) motor which i am very skeptical of buying. Not to mention you cant find one for under $3500 with under 150k.

Are there any other options out there if I do end up having to pull the motor?

 

This is a real nightmare. And then to add insult to injury, withing that same week one of my boats blew a powerhead on a yamaha 150 four stroke...guess when it rains it pours...

 

Thanks.

[muddkatt]

Not saying your mechanic is wrong, but verify that you have no compression on one cylinder first. Usually a broken rod ends with a hole in the block.

[RyanbabZ71]

That doesn't sound good. The denalis have the L9H motors? I thought they had AFM?

 

 

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[L9H 2 LM2]

Not saying your mechanic is wrong, but verify that you have no compression on one cylinder first. Usually a broken rod ends with a hole in the block.

Yes, and I am sure he is not dead set on his analysis either as he just did a quick look over as a favor at no charge and he too would probably recommend doing the same before jumping into this feet first and buying a motor just off of his initial thoughts alone. So at this point, I guess it is now up to me to (A) perform a compression test, drop the oil pan and whatever else needed to try pin point the problem myself or (B) pay him or another mechanic to pin point the problem.

[L9H 2 LM2]

That doesn't sound good. The denalis have the L9H motors? I thought they had AFM?

 

 

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Im am not 100% positive, but I thought the L9H did not have the AFM. I thought this was implemented in the later models like the L94 and L99 (at least thats what I gathered from what I have read). Also, I have driven the 5.3 with the AFM and I know you can feel when the AFM kicks in on these and I have always thought mine did not because you cannot feel this in my truck when cruising on the highway and my fuel millage definitely doesn't concur with this at 12mpg. Now excuse my ignorance on this, but can you elaborate further on what significance the AFM would have on this? Thanks.

[KARNUT]

If that was the vehicle you used to pull your boat it wouldn't be all that unusual to use up the engine at 100K miles. If you have another vehicle rebuild it yourself, how much you spend is more in your control. If you were able to pull the valve covers and intake and put back together you can do a rebuild. There're plenty of how to books to work you through it.

 

 

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[muddkatt]

Now excuse my ignorance on this, but can you elaborate further on what significance the AFM would have on this? Thanks.

 

AFM engines are well known for lifter failure that causes not only a dead miss, but they tick/rattle pretty bad when they fail.

 

I have a couple of questions, does the truck have a dead miss now that it went to making noise? Any check engine lights on?

[Black02Silverado]

Not good at all but things happen. If it did break a rod then more than likely it had a flaw when manufactured. It sucks that this has happened but out of the thousands of these engines built the odds of one having issues is possible.

 

Just like my sister, she had her alternator go bad on her 2007 Toyota Corolla at 97k miles. The shop installed a new one and it turned out that new one they installed was bad as well. My sister seems to always have problems that nobody else has. As picky as she is with preventative maintenance and she purchased a Toyota for the dependability, she couldn't understand why her alternator went out so soon.

 

A friend of mine has a 2003 Suburban with the original engine, transmission and alternator with 350k. I wouldn't believe it myself if i didn't see it and know him personally

 

Again, it sucks that this has happened. I guess you can be great-full that it happened close to home and not out on a long distance trip..

[007matman]

I'm curious about where you end up with this.

 

I bought a 2002 Jeep Grand Cherokee many years ago based on the reliability I'd heard about on the 4.0 engine (my mother in law had one with almost 300k on it and she didn't do any maintenance other than oil changes). Wouldn't you know it? I had to replace the motor at 110k. Not as expensive as what you're looking at but I get the pain you're dealing with.

 

I would have a couple people look at it before I dumped a bunch of money into it. I fixed my Jeep and now it's a solid vehicle. I'd drive it anywhere and wouldn't think twice about it.

 

However, if I had that issue with my Esky I may not do the same.. the 6.2 is really pricey. Hopefully, I don't need to look at that.

 

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[2018GMC]

That doesn't sound good. The denalis have the L9H motors? I thought they had AFM?

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GMT900 gen

Truck 6.2 engines did not have afm.

SUV Denali (Yukon / Yukon xl) did have afm on the 6.2

[L9H 2 LM2]

 

AFM engines are well known for lifter failure that causes not only a dead miss, but they tick/rattle pretty bad when they fail.

 

I have a couple of questions, does the truck have a dead miss now that it went to making noise? Any check engine lights on?

No dead miss at idle. That is what dont add up to me if it was a broken rod. and no, there were no check engine lights on last i seen. Mechanic did say once he revved it a little you could here a pronounced miss but I did not experience that.

[L9H 2 LM2]

Thanks for all of the feedback. I got the truck back in my shop this evening and I have decided I am just going to grab a hold of my balls and tackle this thing myself even if i end up having to replace everything from the crank up. So although i will be missing out on the one of my favorite fishing tournaments of the year, I am going to start taking it apart tomorrow morning....Priorities... I am going to start by pulling the plugs and checking compression so I can try and pin point the cylinder. Then if need be I will pull the oil pan to see if i have any parts laying in there. Ill keep yall posted and we will see where it goes.

 

Also It dawned on today that being this is an aluminum sleeved block, if I have a end up having scarred cylinder I should be able to get it re-sleeved correct? I read some threads on a ls forum that said it can be done easily by a good engine machine shop. If so that will be a lot cheaper than a bare block (which is $1500 if anyone was wondering). Heck who knows, I might just get out of this for under $2000!

[muddkatt]

No dead miss means the rod is not broken.

[L9H 2 LM2]

So I got the motor out and took the head off and this is what I found... What I cant figure out is what the heck could have caused this. There is a large piece of the piston missing all the way down to the piston ring and as you can see both the head and piston is beat to hell and back. The top of the valve skirt is also broken which I dint know is this was a cause of effect.

 

I guess the question now is, what the are the chances of something in the bottom being damaged due to this. Like a rod or bearings or crank... Guess I will fine out tomorrow when I pull the oil pan but I am going to keep my fingers crossed that I will get some kind of luck and get away with a new head, piston and cylinder sleeve. Advise from here anyone?

[L9H 2 LM2]

And her is a pic of the head.