My 89 2500 6.2J (225,000) oil pressure gauge would go to the peg at start up and stay there until it was driven several miles. It would suddenly operate normally then back to the peg when driving in city traffic. This went on for about a year with no problems in performance or oil consumption.

The next thing was a sound like a lifter had leaked down at idle but the performance was normal under all conditions including full throttle upshifts up to 70mph. When the ignition is turned off at idle there is a knocking noise coming from the front of the engine.

Jim
Pensacola, Florida

Oil Pressure Sender is probably failed.

You'll need to pull the oil pan, valve covers and timing cover for a 225kmi inspection - way past due for a timing chain-set.

Requires permatex Black RTV, timing cover gaskets, waterpump gaskets, timing chain and BOTH sprockets.

Closely inspect the harmonic balancer AND accessory drive pulley for rubber deteriroation - extrusion, cracks, missing pieces, etc.

ANY deterioration REQUIRES replacement - put it off till next time, and you'll need a crankshaft and block.

And new OPS unit - the operating diaphragm is heat-hardened