Cherokee Oil pressure problem

[mtulett1]

My oil pressure drops to zero when at idle after my engine has warmed up. Does anyone have any suggestion? It is 2001 Straight 6 with 143000 miles. It started acting up after it overhaeted and stalled out on me a few months ago. Any help would be greatly appreciated. Thanks

[fredjacksonsan]

It could be the sensor, or it could be the actual oil pressure. Have the pressure tested.

[mtulett1]

i have changed the sensor and that didn't work. Other than at idle after car has been running for a while the pressure is fine. I am worried that if i sit for an extended period of time it will mess up the engine.

[MagicRat]

Low oil pressure can be caused by a number of things.

Have you changed the engine oil since it overheated? (overheated oil can become too thin).

Chances are, your engine oil is 5W-30, as specified by the manufacturer. Try using 10W-40 in summer and 10W-30 in winter as a temporary fix. The thicker oil usually builds more oil pressure.

A more permanent fix would be to find the cause of the low pressure. Often, in these engines, the oil pump will wear out sooner than the rest of the engine. A worn pump will not pump hot, thin oil efficiently. The pump can be replaced while the engine is still in the vehicle.

It is remotely possible that the low pressure is caused by damaged engine bearings, but often, such damage is accompanied by bad engine noises.... unusual knocks and clicks coming from the engine.

Finally, using a decent, mechanical oil presure gauge may be handy. These usually are much more precise and accurate than the original electric units. Unfortunately the original gauges are pretty useless at telling the difference between 10 psi and 0 psi.

Engines, especially older ones, generally need only 10 psi per 1000 rpm to survive.
That is, 10 psi at 1000 rpm, 20psi at 2000 rpm, etc, up to a total of about 35 psi. An accurate gauge is required to find out if you are achieving this.

[jlc55]

just got a 98 jeep cherokee sport and the oil gauge started to flucuate..it stays on 40 then suddenly drops down 10 and then shoots up to 40 again..never past 40. I know its not the oil level cuz dip stik reads full... Any ideas would be appreciated!

[mtulett1]

Would the oil pressure drop out if the pressure relief valve stayed open and would it make a high pitched whistling sound also?
thanks

[MagicRat]

Originally Posted by mtulett1

Would the oil pressure drop out if the pressure relief valve stayed open and would it make a high pitched whistling sound also?
thanks

1. Yes, it would.

2, Such high-pitched whistling noises are sometimes due to intake manifold vacuum leaks..... especially if the noise lessens when you step on the gas.

[mtulett1]

thats exactly what happens, then the sound will just go away and it is actually worse in cold weather then in warm weather. Ok so would you change the oil pump while i am in there getting that pressure relief valve? Also if i put a high volume oil pump in is a standard pressure relief valve ok or does it need to be upgraded also?

thanks