I have a knocking 6.2 . It has been knocking for about a year now, I always thought it was an injector but I am not sure. recently the knock has gotten louder so I went to a stanadyne service shop with my truck and the whole time I was there it did not knock, but of course I got home and it was knocking again. I will try to explain the symptoms. When I start the truck when it has been sitting for a while, the knocking is not immediate as the engine starts, the knocking only apears after the engine has been running a few seconds, almost as if when pressure builds up either in the lubrication system or in the injection system. Also the knock apears to sound worse when the fast idle is on , but could just be because the engine is turning faster that it would apear that way. also it is a bit quieter once it has warmed up a bit. Anybody ever experience this? thanks.
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Trying to find knocks with the engine besides me is difficult, trying to find them through words is almost impossible. Every way I know of involves taking things apart. I have run into almost 0 injector knocks in 6.2's. What I have seen: Glow plug tip imbedded into top of piston, worn wrist pin bushings, bad roller lifter, bad rocker arms. Pick a place and dive in. Check bearings while you are at it. It is easy to roll in a new set of inserts to replace worn bearings, it is much harder if you wait until a bearing fails.:eek: :grd:

Sounds like an injector to me or else a leaking lifter. I would isolate the knock to the cylinder that is causing the problem. If the knocking goes away when you loosen an injector line then the injector has a problem. If the knock increases when you put the fast idle on then that is another sign of an injector problem since the timing is advanced and ignition occurs earlier. If it is an injector, I would also take off the cover to the injector pump to see any sediment is in the bottom of the bowl.

A bad lifter can sound at startup due to the lifter leaking down when the engine is off. The leakdown would occur if that paticular valve is depressed. It will sound off until the lifter fills with oil.

A bad rod bearing will always sound off, but more so when you increase the engine RPM's and then let off the throttle fast. They tend to rattle when you do that.

I second what DC said above, every knocking sounds I've been trying to troubleshoot wasn't an injector. Usually if it's a injector, you are going to have a BAD miss, and you'll know it. But, I still take my injectors down to Diesel Injection Service (great to have them locally) and have them test them, peace of mind. Anyways, things to look at basically agree with DC, the lifters, and rockers, and then bottom end bearings, or in a rare case, Glow shrapnel stuck on a piston..

I know that it's not a glow plug tip because I've never broken a tip off. I don't believe that it would be from the bottom end because the knock is clearly from the top end. I had a gasser that had a lifter that would leak down, it would knock when I first started and would go away within minutes. This is the other way around, the knocking will start after the engine has been started for 5 seconds or so, as if a build up of pressure in the system. Could my timing chain have streched enough to change the timing and cause the knock, or could it be the IP? I have 250000Km's on my truck and as far as I know it is the original IP and injectors. I do notice a miss at idle,but not a bad miss. The IP does leak fuel in the valley when the engine is off.

The leaking injection pump needs attention, possibly the knock is an air lock on one of the weak injectors, you say it goes away sometimes. My bet is lifters, my '86 6.2 has a lifter problem, thats the last thing I have left to check, it knocks in one cylinder bad, if you rev it up it's worse, sounds like a rod knock. It misses at first, a real bad shake, then quits missing, and the knock is still there, but faint, only really hear it when you rev it up gain (clank, clank, clank, fast nasty sound). But after running about 2 minutes or so, it will just quit, and sound normal, except the idle does have a bit of a lope. I think I have a collapsed lifter, I'll know more this weekend when I tear into it. Thing about this knock though, it only occurs if you let the truck sit for a week. If it's started every day or every other day, no knock. Just when it sits for extended times and the lifters bleed down, and the bad one really bleeds down and doesn't pump back up fully.

Chevydiesel, I think you are right on track with a bad lifter. I have had a few in the past that would knock periodically and then go away. As for the other valve train noises, I have seen some roller lifters that wear the roller square or have play in the needle bearings which can cause a knock. One thing to remember about valve train knocks is that they will be at 1/2 half the speed of the engine.;)

Just an update...

I did get to tear into the engine this weekend, what a job! Anyways, I found two lifters that were bleeding down, but not completly collapsed. I bought a whole set of lifters and installed them in the engine with the heads on. I have approximatly 350 miles on the new lifters (yeah i went for a joy ride) and now I'm having a completly different problem, my guess one of the new lifters doesn't want to pump up at all. Engine ran perfect for 100 miles or so, then started doing slowly/quickly failing. Ticks badly above 1000 rpm with a load, won't do it at idle or just reving up the engine.. I'm going to contact the certain manufacturer of the lifter because I think from comparison of different lifters that this design/model is flawed.

But, just wanted to let the original poster of this thread know that bad lifters DO cause nasty knocks!