I did a google search using "dodge plenum gasket failure". here are some quotes from hits on the first page.
Answer by 1dennis3
Submitted on 6/4/2004
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I have a 1999 Dodge Ram with the 360 with 55000 miles. I have installed the K&N cold air intake system as well as a throttle spacer, dual Thrustmaster exhaust and reprogramed the computer chip. All this in an attempt to get better mileage. Before all this I was averaging about 9 MPG and now I average about 12 MPG. Over the past weekend I drove it to a lake (300 miles one way) pulling my boat that weighs about 7000 lbs. It cost me $250 in gas and burned 9 quarts of oil! I went to my Dodge dealer and told them of my experience and the mechanic said "I'll bet it was pinging pretty good to" Yes it was. He said that I need an intake gasket. He said that this would solve the problem of burning oil and would help the MPG as well. Has anyone else had this experience?
if the plenum gasket is blown bad you could be running on a half a quart of oil and your gauge is gonna read 40 or so, then you get on the highway and boom your done, game over.
Shirley of Stockton CA (10/30/03):
4-99 I bought a new Dodge Durango. Had the car 2 1/2 years. At 32,000 miles my engine blew. I had previous problems with the oil pressure dropping. When I took the car in they said they needed to replace the intake manifold. It was replaced and still same problem. 6 months later while driving from one state to another for vacation, I hear my engine knocking. Next thing you know it's getting louder and louder.
furyous03-21-2004, 12:11 AM
your first sign will be oil consumption. to confirm, disconnect the PVC and plug both the valve and the vacuum hose to the manifold. then disconnect the breather hose going from the valve cover to the intake hat and check for crankcase vacuum. any more than slight vacuum indicates a plenum leak. Other members have posted you can also check for oil at the bottom of the manifold (looking through the throttle body) but I found checking for vacuum easier than climbing up into my engine compartment.
Defective Engines - Dodge Durango
Posted By: Anonymous on 10/7/2003
Location: Plymouth, MI
I'm the owner of a 1999 Dodge Durango with a 5.9L engine. At around the 78,000 mile mark, the vehicle began to experience sporadic loss of oil pressure and spark knock on acceleration.
Although there was no visible oil leak, it became apparent that the engine was consuming oil. A single inquiry to a competent mechanic brought to my attention your Technical Service Bulletin 09-05-00, which discusses an intake manifold plenum pan gasket oil leak defect common in your 5.2L and 5.9L gasoline engines. Obviously, A defect such as this could quickly have a catastrophic effect on the life of this very expensive engine.
I have no more to say on this subject.
