Please Help - LOUD thumping, blown Lb7???

7969 Views 39 Replies 16 Participants Last post by DieselSpeed, Feb 14, 2007

John LegionST

Discussion Starter · Jan 29, 2007

Driving home from work a few minutes ago and I slowed for a yield sign. When i went to pull away, there was a VERY LOUD thumping. I immidiately thought "exhaust leak" thinking that maybe the downpipe came off the turbo, but that was wrong, downpipe still VERY securly attached.

From the engine bay, there is a a very loud THUMP THUMP THUMP that sounds like a really bad exhaust leak...

I have no idea what it is... any suggestions?!?!?

I'm going to go check for fuel in the oil now.

Truck has 90K miles on it, and is stock excpet for the MBRP and Predator, and it is not beat on at all. Just got back from a 400 trip to VA yesterday.

PLEASE help, thanks in advance for any help!!!

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John LegionST

Discussion Starter · #2 · Jan 29, 2007

UPDATE:

No diesel in oil

Oil level was between the A and F on the dipstick (low 1/2 quart)

Oil Pressure is between 40 and 60 at idle and jumps to 60 if i tap the pedal

Truck fires right up and idles but shakes...

Oh and the tune has been put back to stock...

Still no idea...

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John LegionST

Discussion Starter · #3 · Jan 29, 2007

Another UDATE:

Traced the thumping sound to the intake (it's stock). Opened it up and everything looks ok...

PS - No codes or anything.

TheChevyHDMan

· #4 · Jan 29, 2007

Thumping like air was making its way to the intake? Is it consistent with rpms?
When my 6.5 blew a valve, the air from piston compression would push air up to the intake and make what I believe is the same sound your describing. Is their any excessive smoke coming from the exhaust? Engine feel rough besides the noise( any wobbling)
Thats my best input.
Hope your truck is Ok
Bill

MGlickLBZ

· #5 · Jan 29, 2007

Injectors? Has it been smoking more? Just a thought......

John LegionST

Discussion Starter · #6 · Jan 29, 2007

TheChevyHDMan;1558252; said:
Thumping like air was making its way to the intake? Is it consistent with rpms?
When my 6.5 blew a valve, the air from piston compression would push air up to the intake and make what I believe is the same sound your describing. Is their any excessive smoke coming from the exhaust? Engine feel rough besides the noise( any wobbling)
Thats my best input.
Hope your truck is Ok
Bill

No smoke

Yes thumping is consitent with RPM

Yes the engine feels rough (cab wobbles)

intake sucks in steady pulses

Still havent got it figured out..........

Any tests i could do to see if it lost a valve?!?!? thanks again!!!!!

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MGlickLBZ

· #7 · Jan 29, 2007

I don't know if this will help you but, here goes. I had to have the engine replace in my LBZ at 2400 miles because I lost four glowplugs due to the problems with the early engines. As I was backing out of the JD dealer where I live the truck started "waddling." I quick ran it down to the dealer and it was diagnosed as a bad injector. They couldn't find the glowplugs after they were looking at something else. I thought Iwas going to fall out of my seat as I was driving it there. I also had no issues starting it but it shook like crazy. Good luck.

John LegionST

Discussion Starter · #8 · Jan 29, 2007

Thanks everyone. Still dont know what it is but im out of ideas to try...

Anything else simple i could look at before she heads to a stealership?!?!

If I take it in, is my motor still under warranty? 2002 truck w/ 90K miles.

What should I do when I take it in to make sure im getting the best possible service?!

Thanks again. Hopefully I get this figured out soon! Hopefully it doesnt cost too much...

66flh

· #9 · Jan 29, 2007

Warranty is 100K.Make sure it is all stock.

John LegionST

Discussion Starter · #10 · Jan 29, 2007

66flh;1558385; said:
Warranty is 100K.Make sure it is all stock.

Tune was restored to stock. Only thing on the entire truck that is not stock is the MBRP turbo back exhaust and the 265 tires.

Thanks. Looks like it's time to look for a GOOD local dealership.

Anyone have any suggestions... LOL

John LegionST

Discussion Starter · #11 · Jan 29, 2007 (Edited)

UPDATE: LISTEN TO THIS CRAP

Truck is going to be towed to Faulkner GMC in Bensalem, PA in the morning.

I called another dealership (Peruzzi in Fairless Hills, PA) just to talk to the service manager to make sure my truck should be covered to 100,000 miles and he said "maybe"

He also said that since my truck is "high mileage" (90K on a DMax is high mileage?!?!?!?!?! LMAO) and it's "close to going over the warranty" that GM is going to ask for service records to make sure it has been serviced correctly so that they can honor the warranty...

Now, im no expert but this sounds like a line of BS to me...

I dont have any service records because I bought the truck 2.5 months/3K miles ago.

Safe to say I'm not going to that dealership ever, hope Faulkner is a little more kind!

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slow300z

· #12 · Jan 29, 2007

John LegionST;1558461; said:
UPDATE: LISTEN TO THIS CRAP

Truck is going to be towed to Faulkner GMC in Bensalem, PA in the morning.

I called another dealership (Peruzzi in Fairless Hills, PA) just to talk to the service manager to make sure my truck should be covered to 100,000 miles and he said "maybe"

He also said that since my truck is "high mileage" (90K on a DMax is high mileage?!?!?!?!?! LMAO) and it's "close to going over the warranty" that GM is going to ask for service records to make sure it has been serviced correctly so that they can honor the warranty...

Now, im no expert but this sounds like a line of BS to me...

I dont have any service records because I bought the truck 2.5/3K miles months ago.

Safe to say I'm not going to that dealership ever, hope Faulkner is a little more kind!

now thats a kicker
seeing i got my 04 last aug with 25k on it and now it has 82k and its parked at the dealer right now knowing it needs a gauge cluster,injectors and a few glow plugs

DURAtotheMAX

· #13 · Jan 29, 2007

balance rates??

John LegionST

Discussion Starter · #14 · Jan 30, 2007

DURAtotheMAX;1558599; said:
balance rates??

Good Call!!! Forgot to check those earlier. I think we may have found the problem!!!

Went out and just checked them. Started truck and let it get to 126* ECT. All numbers are in mm. Here's what they read. Should i go let the truck warm up fully and check them again?

Cyl In Park: In Drive:
1 -7.81 -7.81
2 -2.82 -4.59
3 14.16 14.16
4 -3.11 -0.2
5 -1.94 -0.8
6 -0.3 2.03
7 -2.2 -4.59
8 -3.41 -3.23

All nubers are negative except the 14.16 # 3 cylinder that i belive is the problem and the #6 cylider in Drive.

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John LegionST

Discussion Starter · #15 · Jan 30, 2007

John LegionST;1558663; said:
Good Call!!! Forgot to check those earlier. I think we may have found the problem!!!

Went out and just checked them. Started truck and let it get to 126* ECT. All numbers are in mm. Here's what they read. Should i go let the truck warm up fully and check them again?

Cyl In Park: In Drive:
1 -7.81 -7.81
2 -2.82 -4.59
3 14.16 14.16
4 -3.11 -0.2
5 -1.94 -0.8
6 -0.3 2.03
7 -2.2 -4.59
8 -3.41 -3.23

All nubers are negative except the 14.16 # 3 cylinder that i belive is the problem and the #6 cylider in Drive.

Anyone have any suggestions of what to tell/ask the service manager when i talk to him at lunchtime today?!? I want to make sure he checks balance rates but dont want him to assume i have a tuner...

duramaxdiesel

· #16 · Jan 30, 2007

Tuner....what the heck is a tuner???

BudTX

· #17 · Jan 30, 2007

I see no problem with asking him to check the balance rates of the injectors. It will let him know that you are an informed consumer, and might help deflect any attempts to B.S. you with servicespeak.

DieselSpeed

· #18 · Jan 30, 2007

If you're worried about it you could always tell him you've got a buddy in a shop w/ a tech2 that checked it for you, although I'd stick to telling them the problem w/out leading them in one direction or another. If they're competant, they'll find the problem on their own easily enough, and you won't run the risk of leading them down the wrong path.

DURAtotheMAX

· #19 · Jan 30, 2007

dont let them throw injectors at it unless they are 100% sure thats the problem. A balance rate that far off could signify an electrical problem or worse, an internal problem with that cylinder. Make sure they do a compression test...

John LegionST

Discussion Starter · #20 · Jan 30, 2007

duramaxdiesel;1560310; said:
Tuner....what the heck is a tuner???

sorry, hand help programmer... is that better?!? lol

BudTX;1560349; said:
I see no problem with asking him to check the balance rates of the injectors. It will let him know that you are an informed consumer, and might help deflect any attempts to B.S. you with servicespeak.

DieselSpeed;1560431; said:
If you're worried about it you could always tell him you've got a buddy in a shop w/ a tech2 that checked it for you, although I'd stick to telling them the problem w/out leading them in one direction or another. If they're competant, they'll find the problem on their own easily enough, and you won't run the risk of leading them down the wrong path.

Thanks guys, going to talk to him in a few. I think ill stick to telling hiim the problem and mentioning that i know about the 200K mile injector warranty just so that the injectors are on his mind... ill update when i know somehting.

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