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Old 01-28-2013, 09:25 AM
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Oil pressure issues

Ok so we are totally confused and need some help.

Have a 2000 grand Cherokee 4.7 v8. 134,000 miles.

Oil pressure gauge would occasionally drop to 0 and check gauge light would come on at red light. So yesterday we replaced the oil pressure sensor, replaced oil filter and put in new oil.

Ok now when idling the gauge reads 40 and when accelerating the gauge drops to 0 and the check gauge light goes on! Let off the gas and the gauge creeps back to 40?? What the hell is going on? It's doing the complete opposite than before.
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Old 01-28-2013, 02:25 PM
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Re: Oil pressure issues

Is there any indiaction that the pressure really becomes low? (hydraulic lifter ticking or other mechanical noises)
Could be that you bought a pressure sensor with problems.
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Old 01-29-2013, 10:17 PM
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These cheap sensor are prone to fail. May want to verify with a mechanical gauge. You may have a real issue on your hands going to zero with throttle.

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Old 02-14-2013, 02:53 PM
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Re: Oil pressure issues

Older 4.7 have small oil drain back holes that plug with sludge. I don't know if they fixed this with 4.7 in wk. I said before, my brother blew his head gasket likely due to a sludge blockage in an '02 HO overland and my father in law blew his for the same reason in an '01 Durango. Both engines had over 100k on them. I know the oil change schedule on both were not steller either. If your head gasket is still good you may want to try some autorx to try and clean the drain back if they are clogged. It is a slow process that is gentle. Or you could shock treat it with seafoam or another caustic type oil treatment.

The only way to know for sure is removing a valve cover and check to see if you are sludged up. A little manual cleaning could also free the drain backs.
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Old 02-15-2013, 09:00 PM
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Re: Oil pressure issues

I think the poster is asking also why his low oil pressure indicator first came on at idle and, after a new sensor, etc., is does it a applied throttle. Only one way for the sensor connector to go on, right?
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Old 03-03-2013, 09:14 PM
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OK I got a question for someone what dose it mean from just starting my 01 my oil pressure it about 40 almost to 80 and as I drive it will fluctuate in between 40 and 80 and it always stay above 40 would that be the sensor or would it be a something bad ???
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Old 03-03-2013, 10:12 PM
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Re: Oil pressure issues

Quote:
Originally Posted by wj_dubes View Post
OK I got a question for someone what dose it mean from just starting my 01 my oil pressure it about 40 almost to 80 and as I drive it will fluctuate in between 40 and 80 and it always stay above 40 would that be the sensor or would it be a something bad ???
That is the oil pressure sending unit, they are well known to cause problems like this over time.
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Old 03-04-2013, 09:35 AM
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Re: Oil pressure issues

Besides checking the sensor and/or sending unit i agree with DannyVtCa, you must have a clogged oil pick-up tube strainer. Those 4.7lt always has it beyond 120,000 mi. When I had my 2004 Ram 1500 with the 4.7lt and 152,000 mi it started giving me signs with falling rocker arms twice. You might want to check them as well for any sign of clogged sludge and/or getting stuck on the plunger. That all is caused by the lack of pressure because of a clogged oil strainer.
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