Okay, here goes. My 2001 Dodge Ram, Quad Cab, Off-Road, 4x4, 5.9L, 80,000 miles, etc. has what seems to be the infamous Intake Plenum issue... There isn't a lot of oil inside the intake from what I can see, but it uses a LOT of oil and there is some spark-knock under hard acceleration.

BUT! There's another symptom that I've been trying to decide is part of the intake plenum gasket issue or if its something else, like a lifter or something. Once the truck gets good and warmed up, there is a rattleing/knocking noise coming from the area of the intake manifold. It does it at around 1700-2100 RPMs, and when the engine is under a "Neutral" load; meaning not when accelerating or pulling a trailer, but when its just about to shift or say running about 65 or so on a flat highway. The noise NEVER happens when the engine is cold. If I drop it to second gear and drive 25 or 30 MPH I can really hear it, windows up or down.

This has gotten gradually louder over the past year.

Any ideas?

 

i'm wondering if your excessive oil usage is the plenum sucking the oil out, or if its something else related to the knocking noise. it would be real depressing to go to all the trouble and expense of a plenum repair and have it still be knocking. i'd get some various lengths of metal pipe, 1/2 in conduit works good, and use it like a stethoscope to home in where the noise is coming from. if it is in the lifters, at 80k, it might be a good time for a new cam and lifters and plenum, and timing set, and water pump, etc, etc,.... my fingers are tired.