Valve knock, tapping noise

[6.2 Cruiser]

This is my first diesel so it's taken some time to get used to a new set of sounds. Replacing the timing chain (more than 7 degrees of slop) quieted things down enough to hear what I thought was a faint knock from the passenger side cylinders. this has gotten progressively worse over the past thousand miles until now it is very noticeable. I have not yet cracked the lines open to isolate the cylinder. Any guesses? This is a great engine for Land Cruiser, lot's of low end torque, good fuel economy, great on the trail and on the highway. Recently replaced the head gaskets (500psi on all cylinders except one at 430) to stop some outbound bubbles in the coolant overflow line. Now I'm getting concerned about the knocking, doesnt' sound like a rod knock. Also put a quart of ATF and ran it for 300 miles to see if something needed loosened up. Thanks to all those who offered advice and made my diesel conversion a success.

[78Chev]

This may have nothing to do with your knock but here is what mine is. I have a new Avant engine. When I got it it had the stub in it instead of the vacuum pump. When I took the stub out the hex connecting rod came with it, pulling it out of the little nylon retainer that sits on top of the oil pump. When I put it back in there was no way to get the rod fitted right on the keeper because it bottoms out on the oil pump before the retainer groove makes contact. When the oil gets warm it taps like crazy; cold it is not so bad. It's also not so bad after a fresho oil change. I know it is this because when the stub is in there it hardly taps. Since the vacuum pump has a cam in it it alternates pressure on/pressure off of the drive shaft making it tap. There is no way to fix this short of taking the pan off, that I can see, so I'm living with it. I went the route of cracking lines, swapping injectors, checking harmonic balancer, etc., etc., until I found what it was. I don't think it is serious - just annoying. Maybe there is some additive or something a guy could use. Good luck.
Randy

[6.2 Cruiser]

thanks 78Chev. Actually this noise diminishes a little bit as it gets warmer. Going up the driveway in the morning, sometimes I think I can here the rocker arms rattling from that side of the engine. But then again I am brand new to these engines and not sure of what is and what isn't normal. I don't have an auto tranny but kept the vacuum pump anyway to operate the stock Toyota brake booster, works really well. Changing over to hydro-boost was not an option due to all of the other details to look after during the conversion from gas to diesel. Besides, I am hoping someday to use the hydro-boost feed off the power steering pump to power a Mile Marker hydraulic winch...someday.

[Dieselboy]

Based on where you're hearing the sound, it might be a lifter problem. I know that there have been some engines (diesel or otherwise) that only show the symptoms of a collapsed lifter when cold, but after the seals in the hydraulic lifter warm up and accept more oil, it goes away.

When I have had to diagnose problems on my old 6.2L, I used a stethoscope to help pinpoint the exact location of the knock.

That's just my $0.02, but I wouldn't take it to the bank. :D

Good luck!

[britannic]

A mechanic's stethoscope (available from most autoparts stores for around $5-12.00) is the way to go. I was able to isolate a couple of tappets that were malfunctioning within a few minutes. It will also help you to home on other problems if it's not the lifters.