I have a 95 6.5 turbo K2500.
I bought the pickup in january and now I noticed a knock. I thought it was an Injector knock so I put in brand new injectors and the knock if anything got worse. Now When the truck is warm, after sitting for about 30 min when I start it it blows Blue Smoke and chugs, and runs rough for about 30 sec. Once warmed up it runs good but still has a kind of metalic knock to it. The truck only has 105,000 miles on it. I own a 83 6.2 and have always loved it. Until now I loved this one too, now I parked it and started driving my 6.2. Did I make a mistake here. Is this noise in the motor or should I try something else. Thanks
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check the front pulley on the crank. it is a dampening pulley for the accessories.

pull on the belt and see if the accessories move back and forth, the rubber dampening in the pulley goes bad and the pulley tries to spin. ends up knocking back and forth hitting its mounting bolts. something to check.

might also try loosening each injector line while running, see if you can isolate the cyl. making the noise.

Pull you coolant tank cap, top the fluid level off and look for bubbles while running when hot. bubbles would indicate a possible blow head gasket or eroded block.

It doesn't sound good, sorry to hear it, I sure hope it's the drive pulley.

Kevin

I tried Loosening Injector lines and all seem to do the same. Also I forgot to mention that the noise is only noticable at idle if I speed the motor up a little bit I can't hear it.

I am also going to try a compression test as soon as I can but I have to borrow the tester so I want to get the glow plugs out first.

check the dampening pulley like I said befor, it bolts to the harmonic balancer

K

What about the Blue Smoke. The smoke is what got me worried. I know diesels always smoke some but not this bad.

Do you get the blue smoke only at startup? If you lift you foot off the fuel pedal while going down hill do you see little puffs of blue smoke? If you accelarate hard, do you see blue smoke?
What oil are you using?

I get blue smoke on start up mostly when warm, and left sitting for 30 min, and when accelerating. Not sure about down hill. I use 15/40 Chevron for oil.

Your next step might be to have a compression test done.
With only about 10k miles a year, is it driven mostly around town? Short trips where the motor is not fully warmed up?

I drive it for about ten miles before shutting it of. But the person who owned it before was in a big city so it probably didn't get warmed up. I just got the glow plugs out and got a compression tester yesterday, going to check today if I get time. I will let you know.

I ran a compression test. Cylinder #6 is down to 250 psi while the rest of them were over 300. I got the exhaust manifold off yesterday after work. I should be able to get the head off today.

I got the head off and it is cracked between the valves in the front and back cylinders. Also the front and back pistons are cleaner than the two in the middle. Is this because of the cracks. Not sure if I should fix the heads or get a different motor. Any input would be appreciated. Thanks.