LB7: Loud bang/white smoke

Dudgy

Dudgy

Runaway
Jun 1, 2010
416
0
0
Alberta
Bone stock 2002 LB7, just bought this thing, it runs, but runs rough. Bought it to be a parts truck but want to see how much it would be to fix, if it's just an injector then i'm gonna change it and drive the truck.

So the guy said he was driving and all of a sudden he heard a "bang" and truck poured white smoke, he shut it down and they drove it onto trailer and towed it back to the shop.

I checked codes, #7 misfire.
Then checked balance rates, why are 6 of them at 7.00, #7 is obviously the problem, and only #8 reads fine, wth?!


It runs rough at idle and smokes. Plus I have quite a bit of blow-by coming out of the oil fil cap.

I'm hoping I don't have a melted/cracked piston, really hoping it's just the injector that went but would that cause any blow-by?

The truck is in very good condition, nice straight body. Would be nice to get it to run again but if it's piston then i'm probably using the truck for parts.
 
Dirtymaxx03

Dirtymaxx03

Active member
Aug 4, 2009
3,109
1
38
Everyone always has to jump to worst case scenario haha

Does it sound like someone going wild with a hammer and anvil when the truck is running?
 
Dudgy

Dudgy

Runaway
Jun 1, 2010
416
0
0
Alberta
Well i'll pull the injector on sunday and see if I can find the culprit. Put another injector in and test it out. If it's still the same after that I guess i'll pull the head. Or I might just pull the head while I'm that far in and check the piston
 
Dudgy

Dudgy

Runaway
Jun 1, 2010
416
0
0
Alberta
What's that gonna gain me though. If piston is cracked compression will be low and also if cup has lifted. I'm gonna pick one up regardless because I want to have one in my shop for future use. And might as well do a compression test on this one before Sunday.
 
Dudgy

Dudgy

Runaway
Jun 1, 2010
416
0
0
Alberta
That's a good idea. So if I lifted a cup should I have pressure in coolant tank just like a blown headgasket?
 
GeorgiaDieselGTO

GeorgiaDieselGTO

Wants to drive his truck
May 12, 2010
102
0
0
Crossville
Nothing will really cause blowby except a piston/ring problem I would do a compression test and it you have one with no compression you just as well pull the heads. If it lifted a cup it will be blowing coolant out the overflow, not causing blowby. And if you have a LOT of blowby dont even bother with the compression test. Just pull the engine and tear it down.
As for what is a lot of blow by, turn the filler cap upside down on the filler neck. If the cap bounces with the engine running and it hazes more that a minute amount, you have a piston/ring problem.
Seen this too many times on my truck:( good luck:)
 
Dudgy

Dudgy

Runaway
Jun 1, 2010
416
0
0
Alberta
That's what I figured. When he told me what happened I told him to check blowby right away. There was quite a bit so my first thought was cracked a piston. Now that I have the truck I'm leaning more and more towards that. I'll pull the head, not that much work. And then probably proceed with the entire engine lol. And everything else on the truck. What a shame, such a clean truck. Never seen a lb7 this clean under the hood lol
 
Dudgy

Dudgy

Runaway
Jun 1, 2010
416
0
0
Alberta
Well I pulled the head this morning and here's my findings lol :mad:

Definitely a melted piston, and the cylinder walls don't look too pretty. Truck just got demoted to parts truck lol, too bad, it's in such nice shape.



 
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