Screwed maybe?

GregJ77

2004 GMC 2500HD LB7
Mar 18, 2023
27
0
1
Mountain Home Arkansas
So i picked up a deal on this dirtymax. (I thought it was a deal) it runs but warmed up at idle it white smokes. I cant leave it running very long because it dumps oil from what i believe to be rear main, like bad dumps, anyways thats another issue, so i pulled the glow-plugs to do a compression test and cylinder 1. Has ZERO compression. My question is what are my odds of it being a cup or valve or something not so major? I plan on pulling the valve cover and was wondering if i can scope the piston thru the injector cup? I've always wanted a duramax but never could afford one. I've had a few 2nd gen clapped out cummins so i know my way thru a diesel a little bit. I've worked on a few friends lly but never been into a lb7. I know I'm going to have to pull the head probably but i thought maybe i could get some insight thru you guys knowing a few other test i can run before i start pulling parts. Any help is appreciated thanks guys. I traded a 2010 bmw 5 series for 5his duramax with 260k miles. Lifted 6" it was done right. That's another issue if i have to pull this engine it's gonna suck how tall it is. Lmao
 

TheBac

Why do I keep doing this?
Staff member
Apr 19, 2008
15,269
1,562
113
Mid Michigan
Should be able to run a borescope thru the glow plug hole. Thatll tell you if the piston is cracked or broken. Sounds like it needs injectors, though. Oil is probably so diluted and crankcase so full of fuel that its spewing everywhere. What does oil level look like on dipstick? Do a simple paper towel test to check fuel in oil, too. I would NOT run the truck at all until you check the engine over thoroughly.

Honestly sounds like you got the raw end of this deal.
 

2004LB7

Well-known member
Dec 15, 2010
6,275
1,683
113
Norcal
I'd finish testing the remaining cylinders. If they are all zero then maybe it's your gauge or something else you are doing. If it shows good on the rest then at least you have isolated the problem to that one cylinder and can investigate further.

A borescope as Tom mentioned could help without pulling the heads. I don't know if you can fit them through the glow plug holes but I'm pretty sure many will fit down the injector holes

What's the blow by look like out of the oil fill when you take the cap off?
 

GregJ77

2004 GMC 2500HD LB7
Mar 18, 2023
27
0
1
Mountain Home Arkansas
Okay, so all my other cylinders are in the 400's only number 1. Is dead. I am so stumped because the truck runs so good for being a hole in the piston. My scope won't fit thru the glow-plug hole so i probably need to just pull the valve cover and scope it that way. I'm hoping it's valve train and not the piston. I know regardless I'm gonna have to tear it down to really know, i just thought I'd ask a few questions and see what other possible causes there could be. I guess a hole in the piston wouldn't cause a bunch of smoke? Because thats why i am so confused, i figured if i had a hole it wpuld smoke real bad and run like shit. Dont get me wrong, it has a little miss but just kike it would if it had a bad injector. This is another wierd thing, on my balance rate test all the numbers were low and there was NO + or - on any numbers. I am going to post a picture of my balance rates.
 

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GregJ77

2004 GMC 2500HD LB7
Mar 18, 2023
27
0
1
Mountain Home Arkansas
Okay i got an update. I'm kinda happy but still got work to do. it's not a hole in the piston. I'll get the attachments emailed off my scanner in a bit and show y'all. So that's good, i think now im either at a head gasket or valve(s) still. I did find some trash and milk in the cup. Also, when i pulled the cup (i forgot to drain my rad) it filled up my pistons and i heard all kinds of noise from fluid doing something down there, lmao I'm not sure its supposed to do that? Doesn't the head gasket keep that sealed? Anyways i think while I'm in this deep I'm going to pull the heads, inspect further and stud the heads put a good head gasket set on and hopefully be done with that. I have injectors and a complete fuel line kit coming, and im going to replace every single piece of rubber line while im in here too, i found so many leaks and dry rotted hoses. I knew better to get a truck from a kid but he's a family friend and needed a good running car so i did him a favor, and i have the ability to fix shit i just wasn't thinking i was gonna ve into this deep lol. I really thank y'all for chiming in and helping. I'm n

ew here and i can tell y'all are good folks in here man.
 

TheBac

Why do I keep doing this?
Staff member
Apr 19, 2008
15,269
1,562
113
Mid Michigan
VERY IMPORTANT: Where did you buy your injectors?

Glad to hear you have the ability and motivation to repair it yourself. These trucks can get expensive very quickly.
 

GregJ77

2004 GMC 2500HD LB7
Mar 18, 2023
27
0
1
Mountain Home Arkansas
There is a little I've seen worse, but it does have some. I'd like this truck to get me thru the summer then i plan on doing a full build during the winter. I'm really leaning toward it being a valve being the piston looked okay, i figure if it was a head gasket I'd have low compression in all cylinders vs just one. It started getting really cold out so i quit for the day, but im gonna pull the head tomorrow. It sucks because i cant put the truck in my shop i need the room for customers. So I'm doing this truck outside the bay in the parking lot. 🙃
 

GregJ77

2004 GMC 2500HD LB7
Mar 18, 2023
27
0
1
Mountain Home Arkansas
Well, heres an update. I am f*cked. Hole in the piston. The truck has a 6" lift i don't even know how im gonna get the motor out. Lol anyways, heres the picture. I scoped it and didn't see the hole, i really thought it was gonna be a valve. I think the turbo caused it. The wheel has so much play, like almost a half inch of play, so now I'm gonna have to rebuild the turbo. Anyways i think a piece of the turbo broke because the piston is pitted bad like something was in there.
 

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GregJ77

2004 GMC 2500HD LB7
Mar 18, 2023
27
0
1
Mountain Home Arkansas
Drop it out the bottom hehehe

But really if I was to do this then I would take the wheels off and lower it back down with the jack until you get it to where you want.
That was exactly my plan. It just sucks man because i just dont have this kind of money at the moment. She's gonna set a few years for sure.
 

shakenfake

Moron
Sep 15, 2022
181
55
28
Shlumpt, TX
If you really want to do this wildly, which maybe you do, then remove the oil pan and just take out the one rod and piston that is broke via the top of the engine. Super lame way but never have to pull the engine that way :)
 
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GregJ77

2004 GMC 2500HD LB7
Mar 18, 2023
27
0
1
Mountain Home Arkansas
If you really want to do this wildly, which maybe you do, then remove the oil pan and just take out the one rod and piston that is broke via the top of the engine. Super lame way but never have to pull the engine that way :)
In a cummins you can do a in frame rebuild, I've done them, but everyone is saying in another forum you can't in a duramax, that you have to remove the front axle. I guess you cant just drop the pan because the flywheel bolts go into the oil pan. I've also rebuilt a jeep cherokee that way. Im not worried about rhe work or pulling the engine, i just can't afford it right now. We hit some hard ass times in our house hold. My wife got into an accident and been out of work for 6 months now, i could get a loan but where we messed up is, we maxed our cc out and it dropped both our credit down to a 600 and 590 from the 700s. We got hit HARD and i have to have a back surgey that i put off because we cant both be down lol. Someone up there hates me right now.
 

GregJ77

2004 GMC 2500HD LB7
Mar 18, 2023
27
0
1
Mountain Home Arkansas
If you really want to do this wildly, which maybe you do, then remove the oil pan and just take out the one rod and piston that is broke via the top of the engine. Super lame way but never have to pull the engine that way :)
To top that off i traded our only running car ( a 2010 bmw xdrive) for this truck because i wad teying to start a new buisness building bost trailers and needed a truck bad and I THOUGHT i would be helping a family friend out by giving him a good car and took his word it only needed injectors. I found out thru another friend that he knew it needed a piston.
 

TheBac

Why do I keep doing this?
Staff member
Apr 19, 2008
15,269
1,562
113
Mid Michigan
You can either rebuild what you've got, or start looking on Marketplace for a good running LB7 and just replace it altogether.
 
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2004LB7

Well-known member
Dec 15, 2010
6,275
1,683
113
Norcal
I'm with Tom on finding another engine. You can always try and take your time fixing up your current engine for later with a used engine in your truck or you can junk it. Up to you
 
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Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
21,065
4,735
113
Phoenix Az
lets see the rest of the pistons and rotate the engine around so you can take a pic of the whole cylinder. There are ways that are not the "right way" to fix this but ways to get you back running again and it will run just fine on stock power. But we have to hope the cylinder is in good shape and the rest of your pistons are in good shape. i dont condone doing this but desparate times call for desparate measures.

you could be all into it around 1000 bucks or less.
 

Nate’s Dmax

Active member
Dec 11, 2020
173
41
28
I’m right with James here. It’s probably 6 of one or half a dozen of the other as far as how to access the crank. Pull the engine or drop front axle and tranny to remove oil pan. Pulling that piston and replacing with another isnt that bad but here comes the scary part. Almost always it damages the cylinder wall or even blowers the hole on through the wall. As Tom said another engine might be the best way to go. Ive got some used LB7 parts laying on the shelf if you need anything.