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Discussion Starter #1
8 months old.......73,000 miles!

My '06 GMC 3500 has been in the shop recently twice for fuel pressure relief valve failures in the past couple weeks. Today the truck started knocking real loudly, and tripped a check engine light. My bully dog is in the other truck out of state, so I was not able to get (or clear) the codes. The truck does still run, but knocks so loud you would think the engine is blown. It also let us continue driving at 65 mph despite the condition.

Has anyone encountered a knocking in an LBZ yet?

I see a thread about a 'knocking' in 4x4 mode, but that sounds like 4x4 hardware issues.

The truck is bone stock, the bully dog hasn't been in use for months on this particular truck. Even then, it was only on tow/econ setting.
 

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My buddies is knocking right now. Sounds internal to me. He only has 12,000 miles, 100% stock. No codes yet. He says it goes away after a while. I could hear it still hear it after he said that. I told him to take it in.
 

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if it threw a code its 99% certain its something electrical or "external" to the engine.

broken internals dont "throw codes"

you'll need to be more specific than "knocking"
 

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Discussion Starter #5
DURAtotheMAX;1577740; said:
if it threw a code its 99% certain its something electrical or "external" to the engine.

broken internals dont "throw codes"

you'll need to be more specific than "knocking"
It did not throw the code right away. In fact it went 100+ miles before the CEL came on. Likely the knocking issue caused something else to fail (or temporarily fail) to trigger the CEL code. It never did lose power, which is very odd considering how loud the knocking is.

More specific....it definitely sounds internal, as the accessories all seemed to be OK. It sounds like a broken rod or some major issue to be honest. I was very surprised to see it actually made it home. People at the truck stop were asking "what the h_ll is wrong with your truck?" It is audible from over 200 feet away, I know that much. I'll be taking it to the dealership this afternoon, and will keep you posted.
 

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2006LBZ;1577804; said:
It sounds like a broken rod or some major issue to be honest.
you would know if it was a broken rod. ;)

just for kicks, disconnect the batteries for half an hour and restart it...see if you can get the code read too. Sometimes if something electrcal happends, the ECM will shut down half the cylinders, causing it to sound like a meltdown.
 

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2006LBZ;1577804; said:
It did not throw the code right away. In fact it went 100+ miles before the CEL came on. Likely the knocking issue caused something else to fail (or temporarily fail) to trigger the CEL code. It never did lose power, which is very odd considering how loud the knocking is.

More specific....it definitely sounds internal, as the accessories all seemed to be OK. It sounds like a broken rod or some major issue to be honest. I was very surprised to see it actually made it home. People at the truck stop were asking "what the h_ll is wrong with your truck?" It is audible from over 200 feet away, I know that much. I'll be taking it to the dealership this afternoon, and will keep you posted.
Is this the same truck you were having problems with 4-6 months ago and it was stranded at a sub-standard dealer or do I have the wrong guy?
 

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DURAtotheMAX;1577827; said:
you would know if it was a broken rod. ;)

just for kicks, disconnect the batteries for half an hour and restart it...see if you can get the code read too. Sometimes if something electrcal happends, the ECM will shut down half the cylinders, causing it to sound like a meltdown.

Good point. Also good possibility that one or more injectors may be going bad. Fuel knock can sound like the engine is getting ready to come apart.
 

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Discussion Starter #10
MGlickLBZ;1577831; said:
Is this the same truck you were having problems with 4-6 months ago and it was stranded at a sub-standard dealer or do I have the wrong guy?
You are correct, that would be me. The first 54,000 miles were trouble free....the last 20k have been nothing but trouble. Fuel injection pump failure, fuel pressure relief valve, another FPRV a week later, and now a week after that is this issue.

The latest: Local GMC light/medium duty dealer has it, advised it burned up (fried) a glow plug in cyl #3, it came apart, and the piston jammed the parts up/down along the cylinder wall.

The verdict: They are awaiting approval from GM for a replacement engine, as that would be less extensive than having a dealer technician perform a duramax rebuild in the shop.

Will get more info next week I assume.
 

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my brother in laws lly 05 did that but the tech told him it was a fuel knock it sounded like a 01 cummins to me knocking rattling it hurt my ears he traded it he also found out after he traded it it may have had a broken valve spring
 

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Did your truck get the glow plug controller recall done?
 

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2006LBZ;1584125; said:
You are correct, that would be me. The first 54,000 miles were trouble free....the last 20k have been nothing but trouble. Fuel injection pump failure, fuel pressure relief valve, another FPRV a week later, and now a week after that is this issue.

The latest: Local GMC light/medium duty dealer has it, advised it burned up (fried) a glow plug in cyl #3, it came apart, and the piston jammed the parts up/down along the cylinder wall.

The verdict: They are awaiting approval from GM for a replacement engine, as that would be less extensive than having a dealer technician perform a duramax rebuild in the shop.

Will get more info next week I assume.

Sorry to hear about the problems.

I also had the engine replaced in my present truck due to glowplug related issues. My truck ate four of them even before the recall came out. I wouldn't be worried about a replacement engine because all they do is plug it into the wiring harness. Stay on top of it with GM. I assume that you called GM and told them how disappointed you were etc. I have heard of GM telling the dealers to just rebuild the engines. Did the sub-standard dealer do anything with the electronics on the engine? One more reason to keep it away from that place. Good luck.
 

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I woudl fight very hard before they rebuilt mine
 

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oh if he did not get the glow plugs reflashed might have came apart and dammaged the motor still request them to replace the long block before the warentee runns out .
 

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Discussion Starter #16
catch03;1586427; said:
oh if he did not get the glow plugs reflashed might have came apart and dammaged the motor still request them to replace the long block before the warentee runns out .
Thats what I am shooting for. I don't want a "damaged" engine simply "fixed up" for now, and then it craps out just out of the 100,000 warranty. The dealer said if the rebuild cost exceeds a certain percentage of replacement, they will simply replace it. In this case, they feel the engine has substantial internal damage anyways, which may leave GM no choice. All I know is this is likely going to take a while, all of which is time that I have drivers sitting and not making money, and my expenses keep on coming no matter what. AGH!!!

I believe the flash update was done prior to my purchase. I didn't get this one until June 06, and the update had been out for a while by then. I will double check. Even if it wasn't, it has been to the dealership for all service work, and they are to check for open recalls or campaigns. (Most smart service people check for this, as it builds more billable hours to the repair order, even if they are warranty repairs)

I hope to know more tomorrow.
 

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Reading this worry's me greatly.....I need to make sure the recall was taken care of...If not need to ASAP!!
 

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Discussion Starter #18
As of today:

They are telling me that the glowplug burned up, and 2 injectors stuck and dumped tons of fuel into the engine. They don't know which happened first, but the entire head on the one side is trashed, along with pistons and other stuff on that same side. They have told me that GM is going to approve a replacement engine for this truck, because the damage is so extensive.

This is fine by me, as this particular truck has been a bear to me. A new engine will be like having a new truck again. I'm happy. I'm going down to the dealership today to see this all for myself, as I have not been there personally since last Tuesday when I dropped it off. More to come....
 

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Bought my 06 in July and the reflash was done when I took it in for minor warranty stuff in August. I'm amazed so many of today's dealerships can't take a few minutes to deliver a new vehicle having all updates and TSB's installed. Would think that would be a way to address the JD Powers scores
 

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auwing, when was your truck built? I bought mine in like March/April of 06 and it is outside the serial number range for the reflash. Just curious.
 
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