Knocking sound and smoke

[jbsaxman]

OK, all, got a problem. I've done a TON of searching on the other place, but just need to bounce some ideas off of everyone.

Long story short, my rig has a knock. It doesn't occur right away, usually after a few minutes of the engine running. It comes on gradually, starting with a single knock, then it goes away, then it comes back for a couple of knocks, then it goes away, then it comes on full strength. If the engine is warm, it knocks right away when I start the engine.

That said, before I go further, I already know that my rig has a bad #2 piston. I had intended to replace it when I replaced the head gasket and discovered it, but I couldn't get the pan off and didn't have the ability to pull the motor.


So here is what I have tried:

#1 - I removed the serp belt to make sure it wasn't an accessory.
#2 - I have thoroughly inspected the Harmonic Balancer and the Balancer pulley for cracks.
#3 - I have managed to crack 6 of the 8 injector lines. I couldn't get the number 4 or the number 8 lines cracked. The engine quiets down a bit when I do, but the knock is still there.

So, after doing all the research I can, here are a few thoughts I have as to what it could be.

#1 - A stuck injector. If it is, what is the best way to fix that? The injectors are rebuilds that a reputable member of both places sold me. They were replaced about 6K miles ago.

#2 - A bad injector line? I know that there is some buildup in the lines that if busted loose can injector issues. When I pulled the passenger head I was as careful as I could be about removing the lines, but it's possible that I bent the lines. If that is the case, is the only recourse to replace the lines?

#3 - Misfire in the #2 cylinder? (Here is a pic of that cylinder)

If it is a misfire on this cylinder, it would also explain the white smoke I see all the time.

If it is either 1 or 2, it is a relatively easy fix. If it is number 3, then I guess I will just have to wait until I can pull my motor and rebuild. I am planning to do so this winter, which will include new pistons and new DB2 IP and injector lines.

What do y'all think?

 

[Acesneights1]

How's the oil pressure ? What you describe to me sounds like a rod knock/spun bearing. Not good. You need to pull the pan. Put whatever socket fits the connecting rod bolts onto a long extension then go on each rod and pull side to side. The loose one is the knock.If you have a bad piston it's probably that cylinder. You shouldn't be driving it anyway. Sounds like a tear down is in order.

 

[Acesneights1]

Weird I couldn't see your pic the first time. Looking at that ..You definitaly should not be driving it. Not if you want to reuse that block.

 

[jbsaxman]

Oil Pressure has been fine, right where it should be at 40 lbs.

You think it's a rod knock or spun bearing? When I drained the oil last (which I need to do an oil change again soon) there was no metal in it whatsoever. I even took a magnet to it. Of course, I didn't send any of it off to be analyzed.

If it were a rod knock I would have expected it to be consistant and to get louder as the engine RPM's go higher. I did do an overhaul on a car where I did fubar one of the rod bearings and it spun on me (that was a half a$$ed overhaul on a car I didn't care about) . In that instance the knock was always there from the time it started until the time it shut down and it only got worse as the engine RPM increased.

 

[vail426]

What do you suppose broke the piston? It is probably the source of your noise, or at least it would be my first suspicion. Are you saying you replaced a head gasket, saw a broken piston and then re-assembled? What was the reason to replace the gasket? The engine, as Aces said, should not be run.

 

[gmctd]

Bad injector will cause a knock - doesn't matter if it was just "rebuilt" - some folks consider "rebuilt" soaking in carburetor cleaner, etc - some rebuilds don't fix the bad injector - find the knock by cracking each injector pipe at the injector end - switch the suspect injector from the noisy cylinder to any another cylinder: the knock will follow the bad injector - if the knock stays with the cylinder, then valvetrain (rockers, lifters, valves) or further in, such as piston, wristpin, rod bearings, etc - no need to rip the pan off before you've eliminated the other possibilities

 

[jbsaxman]

I have no choice to run the engine for now. That was the reason I put it back together with the bad piston still in place. All things being equal, I would have replaced the piston when I had the head off. But, I couldn't get the front differential down, which means I couldn't get the oil pan off. Had I the cherry picker, I would have pulled the motor, but I didn't.

GMTDC, I will see if I can get the other two injector lines cracked open tomorrow. The remaining ones are the injector right next to the turbo and the one against the firewall on the pass side.

Regardless of what the problem is right now, the motor is getting pulled this winter when I won't be dependant on the truck as much. At the very least, it will get new piston rings (or new Mahle pistons since they are close enough in price to justify it), plus new rod bearings, crank bearings and oil seals. If the crank is bad, then I'll have to spring for a new crank, so I'll get a Scat.

But I'll just have to wait and see what it looks like when I get it pulled.

If they still have it, I know where I can get a bottom end for $200 that was running when it was scrapped. I am not sure of the casting number, I didn't check that when I went to look at it. Should have. Worst case, if they still have that, I'll just buy that block and build a new motor up to put in.