I have a 2002 jeep wrangler sport and the oil pressure is fluctuating. It is very low after restarting engine when it is hot. Check gauges light comes on until you give it some gas then it comes up slowly. I have had it to the dealership and have replaced oil sending unit, oil pump and instrument cluster. Still happens. They have hooked it up to manual gauge and everything is fine. No noises out of engine at all. Help!!!

Complete engine teardown.

The main bearings and connecting rod bearings. The cam bearings. The wrist pins. These are the first bearings that get oil from the oil pump. When you take the oil pan off to replace the pump pull one of the rod caps and check for scaring and color change.

That is a good sign, it is working, my oil pressure fluctuates like a tachometer, at idle it is low, like 20 lbs, then when I 'm cruising, 35lbs, but it goes up and down when you pump the gas. The pressure gauge is reading the oil pressure at the top of the engine, it will show 45 lbs with only 1 qt of oil in there, it is not an oil level gauge. You might have an oil light buried on the dash somewhere that will light up if the oil gets too low. ,, Now about that coolant leak, it should have nothing to do with the oil pressure. Is it a hose? Radiator? Joint at the top of the engine? Where is it leaking, and what is it doing? Does it over heat? Or did it overheat? Is there oil floating at the top of the radiator? Does it blow steam out the exhaust? Does it have coolant or just water? Check it out. hope this helps.

If the engine isn´t making any abnormal mechanical noises, then I would expect the oil pressure sending unit at fault.
If however the engine does make more or abnormal mechanical noises, it could be a too low oil pressure and this should be addressed immediately.

The oil pressure specification for your engine is 13 PSI at idle hot, 37 to 75 PSI at engine RPM higher than 1600. I suspect your oil pressure gauge sender unit or gauge is inaccurate. I would have a known accurate mechanical oil pressure gauge temporarily screwed into the present oil sender unit to verify actual pressure.

If you have the correct pressure I would replace the sending unit first.

You better put a manual gauge on your engine and make sure you have oil pressure. Could just be a faulty gauge or sending unit but I sure as heck would be checking it with a manual gauge.

The check gauges light is normal because at 400 rpm it isn't running fast enough to build sufficient oil pressure. I am guessing maybe a vaccum leak???

When the gauge is at 0, is there any noise from the engine (tick, knock etc?) I would have someone put a mechanical gauge on there and read true pressure.Your driving pressure seems OK but if the low number is "real" something is wrong!

As long as it's not going down, and the engine isnt knocking, you do not have a terrible problem. I have used marvel oil in ones that do this and most times it clears up. If not, change the pressure switch. (Takes a few days before it get's better with mm oil)

If grounding the dash does not work, try putting a mechanical gauge on it and reading actual oil pressure. Pressure does change while driving, but should not wander. With mechanical gauge, check that running hot at idle (in gear if automatic) pressure should not drop lower than 15psi (I'd rather see 20) High reading should be around 40 -50 but no higher.Low pressure indicates a loss of supply or bad bearing on the crankshaft, high pressure may be caused by sticking pressure relief or restriction in an oil passage.