Question about 2000 Jeep Grand Cherokee

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Low oil pressure reading 1990 jeep cherokee laredo

I own a 1990 4.0L inline 6 jeep cherokee when I first start it the oil pressure is between 40 and 50psi, then after about five minutes it slowly goes down. The lowest its been was aroun 10psi after driving it for a little. When on the highway and when accelerating the pressure goes back up to about 25 to 30psi. I ordered a new oil pressure sending unit wich should be hear in a week. I did change the oil and filter using 10w30 synth. blend and Fram tough guard and it helped for a little. I have now smoke from tailpipe or even a smell. I have no problem changing the pump. I just picked up some STP oil treatment to see if that helps.

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If this is a high mileage vehicle, say 180k or higher, treatments are not going to help. As mileage increases, the tolerances and clearances in the mating parts increases. This will lower oil pressure. I have a 90 Safari with 192K. Oil pressure was identicle to yours. I put new rod and main bearings in it and now it never goes below 40 psi, even when hot and idling. I tried additives and all I got was more trouble, It started smoking and using a qt. of oil every 300 MILES. I put valve stems seals in and it helped alittle but not near enough. It is now parked and driven only when have to. This is a result of the previous owner of my vehicle not changing oil at regular intervals and overall poor upkeep of it.

Good Luck

Posted on Feb 27, 2009

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