Tapping noise

[Georgethewelder]

My 88 6.2 recently started a lifter taping noise I replaced the lifters and heads the cam looks ok and oil pressure appears ok as well but it still taps I'm thinking it oil volume related ?

[DmaxMaverick]

Welcome aboard, George!

There may be several causes that commonly get mistaken for lifter noise on these engines. I'll list the most likely suspects, in no particular order......

Harmonic balancer. Check the rubber insulator. Hard and cracked, or soft and gooey, no good. It should be about the consistency of a good tire bead.

Isolated crank pulley, if it has one (likely on an 88). They fail with the same symptoms as the balancer. This causes the pulley to rotate on the hub, and hammers at the "stops". The design is similar to motorcycle drive hubs with rubber insulators, if you're familiar.

Injector(s). When they begin to fail, they will sound like anything from a lifter/rocker knock, to a rod bearing about to exit the oil pan.

Vacuum pump. They get noisy when they go, and are driven by the cam (having the same timing as the valve train).

Although less likely since you've recently laid eyes on them, the rocker rack retainer buttons can come loose or break off, allowing the rocker to float along the rack. Sounds just like a lifter knock, most of the time, until a push rod bends.

[Georgethewelder]

Dear DMax
Thank you for your reply I can go into more detail now that I know someone is looking It all started with a rocker tap quite at first then louder it was maybe a week before I got to it the engine is maybe 5 years old I take care of stuff for a living its had good care I live in the truck . I first changed the rockers on top it still tapped. I noticed that an exhaust valve in the middle of each bank looked a little hammered I pulled the heads I was contemplating pulling the pistons and cleaning up the cylinders and putting pistons and rings but the stuff looked brand new so I just put new lifters and the heads new Injection pump and nozzles.When I installed the lifters I always put them in a small bucket of oil to get the air out I assembled the engine it sounded great no noise after some time the taping slowly came back I think the lifters in the middle must be starving for oil are they fed through the cam bushings form each end ? I am going out there now to pull the oil pan I am thinking I am going to buy a high voulume oil pump I am going to try one last thing then new motor I must get the rig going Thanks for listing

[DmaxMaverick]

It isn't the pump, as long as you are not seeing an extremely low pressure issue. The high volume "squirt block" oil pump is NOT recommended for non-squirt applications, for several reasons. More is not necessarily better, in this case. If the pump needs to be replaced, use a standard volume. If you NEED a high volume pump to compensate for another failure, it will be a short term band-aid, and it comes with baggage of its own, despite everything else.

Simply submerging the lifters will not prime them. Most of the time, they will pump up very quickly during an initial engine oil prime, but these are notorious for taking a long time to prime, in the engine. It happens often enough that I don't count on it. When I get new lifters, I disassemble and clean them, then assemble them while completely submerged in fresh oil. It isn't too difficult or time consuming, but is much more reliable than even the best priming tool.

A similar issue is being discussed in THIS THREAD (http://www.thedieselpageforums.com/tdpforum/showthread.php?t=43323).