Lost of Oil pressure

[jeeppyfan]

My sun just bought a TJ 4.0 liter 2000 (manual) two months ago with 82,000km on it.
Problem: It ran fine untill he changed oil and filter. since then, when hot, oil pressure drops to "0". Coolant level ok, oil level ok, check gage light turns "ON". He had oil pressure sensor changed with no luck. While at neutral and idle, pulling oil dipstick out, I can ear air being sucked thru pipe that helds dipstick. What is it? PCV valve stucked? oil pump defective or else?

[MagicRat]

I strongly suspect there is a problem with your engine that was 'covered up' when you bought the Jeep.

First of all, that vehicle is now 7.5 to 8 years old. 82,000 km is simply unbelievably low mileage. I wonder if the odometer was rolled back, (an easy thing to do for a crooked dealer to do.)

The engine could have many hundreds of thousands of km on it and simply have worn components (oil pump most likely). If this is true, then using a very thick engine oil, such as 20W-50 would boost the hot idle pressure and mask the problem. When you changed the oil and put in thinner, 5W-30 oil (as the manufacturer recommends) the worn pump cannot build the correct pressure.

This is easy to varify. Change the oil and filter and use 20W-50 this time. If the problem goes away then you know the pump is worn (probably the engine too) and likely the odometer reading is false.

Finally, the dip stick sucking sound might be another cover up, but I am not sure. These engines do not have a PCV valve; they use manifold vaccuum sucking through a 'metered orifice'. Therefore, a small amount of sucking is normal. However, if it is substantial, then possibly someone made the orifice larger, to suck more...... and will hide the excess blowby produced by a worn engine.

[jeeppyfan]

Well, I think you are right, we'll do the oil change test and let you know. It sounds like the oil pump to me as well. Any idea of how much it would cost to replace the pump? It's so sad, my sun is 19, working hard for his money and always have problems with his cars.