My 6.2 died so I got a "good" used 6.2 Good Wrench reman. I put it in started it and it sounded good on high idle. Oil pressure was 50 psi on the starter and 75 psi running cold. The pump timing was advanced about an eighth inch and it rattled some. I shut it down and moved the pump back to the factory marks. Sounded better and smother. I then brought the rpms up to about 1500 and all of a sudden all kinds of bad noise came out of the motor. I still had 75 psi oil pressure, it sounded like a metallic rattle. I could not tell where it came from. I shut it down. I left it over night and pulled the shut down wire and cranked the motor to listen. I got 50 psi oil and could pick out a single metallic like rattle. Ideas? Thanks for any input. PK

Check the pulley in front of the harmonic balancer. It has rubber in it that can wear. Mine was bad and it sounded awful.

Here is a short video of how mine sounded before I fixed it.

http://i123.photobucket.com/albums/o283/Mikeyvon/th_suburbanrattle.jpg (http://s123.photobucket.com/albums/o283/Mikeyvon/?action=view&current=suburbanrattle.flv)

I had a balancer fail on a mechanical 6.5L, and same as the movie posted, it sounds absolutely NASTY! I thought that I had a broken crank at first.

Yep, sounds just like that. I've had a 6.2 sense '83 and never had a damper go bad. How do you check it? Is it physical loose? Thanks for the clip. PK

mine was actually the pulley in front of the balancer. I could easily see it was bad. Looks like it is called the vibration damped accessory drive pulley, i cannot find any pictures of it.

Grab the outer ring of both the belt drive vibration damper and the harmonic balancer and see if they move at all. Probably be a good idea to actually pull both parts and visually inspect both sides of em.

I did have one of the belt drive vibration dampers fail once too, it would make one loud knock when you started the engine and when you shut it down, but was quiet otherwise.

I'll attach a picture but I started looking first for a broken valve spring. When I pulled the right valve cover I found two bent push rods next to each other. As you can see they look like twins. Same cylinder. The rocker arm bolt was not tight here. Any comments as to cause are welcome. PK

http://i136.photobucket.com/albums/q195/daybreakfarm/62DieselBentPushRods001.jpg

was there still a whiteish nylon rocker retainer on those 2? you might see a pair on the other two cylinders of that head. they are known to fail.

Are you refering to the round retainer for the rocker arm or is this something on the push rods? Also I've sense notice the rocker arm is cracked right at the bolt hole on the bottom. The end of the rocker arm is bent up about a 1/16th".

I think I'm up with you now. I looked at my pdf military manual. The lifter guide plate is still in place.

Any possible way something fell into that piston and prevented both valves from opening? I'd personally want to pull the head and see what is hiding inside the combustion chamber...

I got the new rockers and push rods in. Started it up and still have a loud clatter. It sounds like the lifters are rattling. I pulled the valve cover and the push rods are ok. They were just as tight as the others. I have good oil pressure . Any Ideas?