Hey guys, I am new to the forum. I have a 2000 cheroke xj sport. I noticed after driving for a few miles when the engine is heated up, the oil pressure gauge drops to 0. I took it to my mechanic, he lifter the manifold, confirm no crack in the cylinder head, and its holding antifreeze. I tried replacing the oil pump, but that turned out to be a waste of money. He did say that there was a little bit of sludge in the engine, but Im running out of ideas. Any help would be appreciated. Thanks.

 

Did your mechanic check the pressure with a mechanical gauge?

 

I am actually not sure, he said he did some "testing" and I guess he thought the oil pump was the issue. But I heard the oil pump usually doesnt go bad. Maybe just the sensor? The engine light is also back on.

 

Start by checking the pressure with a mechanical pressure gauge connected where the oil pressure sending unit goes. you should have 49psi +or - 5psi. If you have good pressure either you have a bad sending unit or the port for the sending unit is pluged.

 

I am truly amazed at how many 4.0s have this problem, especially year 2000. Do some Google searching and you will see what I mean. I can tell you this from experience....it won't hurt a thing! Mine has done that since I bought it. New pump, check bearings and nothing found to be bad. 20 psi at highway speed, 20+ mpg and no oil consumption. Will rum interstate all day long at +70. 70% of my driving is stop and go city with lots of idling time. Hope this helps to put your mind at ease! It does take some getting used to seeing the gauge read zero. I was so freaked out I bought a spare engine (it is still sitting on a stand).

 

I guess the point is that the 4.0 will last a few minutes running at 0 oil pressure before it blows up but will last a long time running at normal oil pressure while showing 0 on the gauge.

To each his own but I would rather have my gauge showing the actual pressure.

 

My dash gauge reads zero. Test gauge reads 4psi @ 650 and 20psi at cruise speed....been that way for years.