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Need some insight and knowledge please !

hudson2000

NAXJA Forum User
Location
Antioch , Tn
I have a problem with my 1999 Jeep Cherokee. It has 177,000 miles, 10w30, 4.0 I6, 2x4. My problem is when I start the engine the oil pressure is where it should be. When I drive for ten to fifthteen min and the oil heats up and then I come to a stop or place the Jeep in park the oil pressure gauge drops to zero. There is no noise in the engine and no knocking that I can hear, the check gauges light comes on. When I put it back it drive , the gauge jumps back up where it is suppose to be and the light goes off. I change my oil every four to five thousand miles, rotate my tires, check fluids every other week.

Can somebody help me make sense of it. Or what they think I should do ? Thank you in advance.
 
Problem # 1 - ITS TWO WHEEL DRIVE hahahha JK atleast you made the right decsion and got a HEEP.

Problem # 2 - Replace the oil pressure sending unit, very common for cherokees. If you look right above the oil filter you will see it there. What I did was I just put an Auto Guage on and I know it reads right all the time now.

With it going to zero and the CEL turning on it aounds like the sending unit. Also I tried a heavy grade oil like some 50W. The stock gauge seems to be able to read that about 98% of the time and for a daily driver thats pretty good.
 
If your pressure TRULY was going to zero, you would hear it in the engine.

Most likely the oil pressure sending unit. I buy these directly from Jeep for best reliability/accuracy/mating with your factory gauge. Worth the extra $20. I have had poor luck with aftermarket oil pressure sending units.

As mentioned, getting your mitts on a MECHANICAL oil pressure gauge and confirming it is another step to peace of mind. Many parts stores rent this tool for a few bucks.
 
This is very common and is almost always the sending unit. The exception is usually an 0331 head that cracked and was ignored letting ran watered-down gradually kill the bearings.
 
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