strange knock 91 Dakota 2.5l

Complete engine rebuild about 2 yrs. ago including replacing cracked head. Suddenly a sound exactly like a rod knock appeared. Replaced bearings but neither crank or bearings showed any signs of wear. Problem was not solved. Under no load (hood up) the engine has a loud buzzing rattle at about 2500 rpm. I can't locate the sound source. Arghhh. Ideas? Thanks

xv920r, hard to diagnose without hearing. I always get a plastic handled prybar and while engine is running safely place it at various locations and put my ear to the handle and listen. This acts as a poor mans stethoscope. How is the oil pressure and is this the Chrysler or Jeep 2.5 in your truck?

The oil pressure is right on spec. On the road I hear the noise as the engine is "floating" at minimum load...just as bad bearings would. It is more apparent when the engine is warm. I tried heavier oil before I changed the rod bearings...no effect.

Engine is Chrysler ohc 2.5l.

xv920r, maybe the balance shaft in the engine, sometimes they can be noisy. A lot of the 2.5's were noisy, I've had a few in cars but the noise never hurt anything.

Engine is Chrysler ohc 2.5l.

you think it might be a rist pin to piston?

I would probably just drive it, I know the noise is annoying. Maybe you could get a oil analysis just to determine wear metals.

Complete engine rebuild about 2 yrs. ago including replacing cracked head. Suddenly a sound exactly like a rod knock appeared. Replaced bearings but neither crank or bearings showed any signs of wear. Problem was not solved. Under no load (hood up) the engine has a loud buzzing rattle at about 2500 rpm. I can't locate the sound source. Arghhh. Ideas? Thanks

have you tried taking belt off for a min. and start it and see if noise leaves if it does it may be your harmotic ballancer? just a thot...

good luck.........