Bad injector/head gasket symptoms

[dk2429]

Brother that owns a welding business has a whole fleet of Duramax work trucks. I went and just helped him out a bit today and went to start up one of the trucks that had been sitting for a while un used (2005 with the LLY.)

The truck sounds like it's making a loud "knocking noise." Almost like an old IDI 7.3/6.9. Something I did notice was the coolant tank being black, which I assume means a blown head gasket, but not sure if a head gasket would cause it to make this noise. The truck also has very little power. I'm thinking maybe an injector shot, but there's no white smoke. When you turn it off and go to start it again, while you're cranking, it'll fire for a split second, go back to cranking, then will start up.

Also to add to that, I did drive the truck months ago to help him deliver stuff on a flat bed. It would run fine, but if you really got on it, it would go into limp mode (wouldn't go over 50mph) and would make that knocking noise at idle. Only now it's louder/worse.

I also did notice that when you turn on the AC to "5," the knocking gets even louder. 220k miles

He's most likely just going to get rid of it as is, but I'm curious to what the problem may be for future reference.

 

[Novak]

Brother that owns a welding business has a whole fleet of Duramax work trucks. I went and just helped him out a bit today and went to start up one of the trucks that had been sitting for a while un used (2005 with the LLY.)

The truck sounds like it's making a loud "knocking noise." Almost like an old IDI 7.3/6.9. Something I did notice was the coolant tank being black, which I assume means a blown head gasket, but not sure if a head gasket would cause it to make this noise. The truck also has very little power. I'm thinking maybe an injector shot, but there's no white smoke. When you turn it off and go to start it again, while you're cranking, it'll fire for a split second, go back to cranking, then will start up.

Also to add to that, I did drive the truck months ago to help him deliver stuff on a flat bed. It would run fine, but if you really got on it, it would go into limp mode (wouldn't go over 50mph) and would make that knocking noise at idle. Only now it's louder/worse.

I also did notice that when you turn on the AC to "5," the knocking gets even louder. 220k miles

He's most likely just going to get rid of it as is, but I'm curious to what the problem may be for future reference.

Well now this thread turned into garage sale. Rofl

You wouldn't necessarily push white smoke once your head gaskets start going out on a "stockish" truck. They usually push water out of the overflow causing the coolant to darken. In my experience loosing a head gasket can cause a lot of mysterious symptoms because you lose compression.
Does it have morning wood?


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[Burn Down]

Need to ck the usual lly wiring problems, harness at the ficm bracket, #2 and7 harness pigtails and ice pick all 8 injector connectors.

And yes it sounds like it’s loosing the head gaskets. As Novak mentioned is the upper rad hose still hard after the engines cooled off?

No codes?

 

[WVRigrat05]

Sounds like bad injectors and bad gaskets. Injectors are probably returned by too much fuel causing the limo issue and the #2 and #7 harness issue is causing the knock.