Oil Sending Unit...
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Member
Joined: Mar 2012
Posts: 205
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From: Severance, Colorado
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0 litre, line 6
Hey everyone hope I don't bug to many people with this post....anyways the last two days ive put 500 miles or so on my jeep from going up snowboarding....last night I was almost home when my oil gauge blasted all the way up to 80 and fluctuated in between 50 and 80 the rest of the way home. It was after a stop for food, and hadn't acted up at all before that. So when I got home I check all my fluids....guessing my 00 head may have cracked or my head gasket went...all looked good fortunately and I double checked this morning for chocolate milk oil or exhaust smelling anti freeze. so im assuming it is my oil sending unit? would that be a correct conclusion?....if so what kind of oil sending unit would you recommend....ive heard the ones from auto parts stores aren't very good at all...thanks for your time sorry if theres already threads on this.
CF Veteran
Joined: Sep 2011
Posts: 4,172
Likes: 4
From: Riviera, Texas
Year: 1998 Sport
Model: Cherokee
Engine: 4.0
Hey everyone hope I don't bug to many people with this post....anyways the last two days ive put 500 miles or so on my jeep from going up snowboarding....last night I was almost home when my oil gauge blasted all the way up to 80 and fluctuated in between 50 and 80 the rest of the way home. It was after a stop for food, and hadn't acted up at all before that. So when I got home I check all my fluids....guessing my 00 head may have cracked or my head gasket went...all looked good fortunately and I double checked this morning for chocolate milk oil or exhaust smelling anti freeze. so im assuming it is my oil sending unit? would that be a correct conclusion?....if so what kind of oil sending unit would you recommend....ive heard the ones from auto parts stores aren't very good at all...thanks for your time sorry if theres already threads on this.
Thread Starter
Member
Joined: Mar 2012
Posts: 205
Likes: 0
From: Severance, Colorado
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0 litre, line 6
Senior Member
Joined: Jan 2011
Posts: 645
Likes: 1
From: Dalton, MA
Year: 1998
Model: Cherokee
Engine: 4.0 H.O. 180K miles
This has happened to me after changing my oil before. In fact I changed it a couple weeks ago and it has been happening occasionally climbing hills. Last time I changed oil filters and the problem subsided. However if you haven't changed anything recently and it just started acting up I would definitely fiddle with the sending unit itself and see if it returns to normal
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 103
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
Remove the oil pressure sensor connector (located just behind the distributor). Use a 27 MM deep socket or short open end 27 MM box wrench, or a short 27 MM open end wrench to remove the sensor. Do not use a cresent wrench or pliers to remove the sensor, any shear (side) load on the threaded portion of the sensor may break it if side loaded too much. Hook up an oil pressure test gauge, like in Bbasso's post, start the engine and observe the oil pressure at idle, then at around 1,600 RPM when the engine has come up to operating temperature.
Minimum oil pressure is 13 psi at idle and 37 to 75 psi at 1,600 RPM. 75 psi is the oil pump relief valve setting.
You can borrow (security deposit required) the test gauge kit from auto parts stores like O'reilly or Advance Auto Parts. The oil pressure sensor adaptor on the engine has a 1/8" national Pipe Thread hole for the sensor, so you'll need to select the proper adaptors from the kit to hook up the gauge.
If the oil pressure is wandering around low-high, up to 80 psi at idle the oil pump relief valve MAY be faulty.
Minimum oil pressure is 13 psi at idle and 37 to 75 psi at 1,600 RPM. 75 psi is the oil pump relief valve setting.
You can borrow (security deposit required) the test gauge kit from auto parts stores like O'reilly or Advance Auto Parts. The oil pressure sensor adaptor on the engine has a 1/8" national Pipe Thread hole for the sensor, so you'll need to select the proper adaptors from the kit to hook up the gauge.
If the oil pressure is wandering around low-high, up to 80 psi at idle the oil pump relief valve MAY be faulty.
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Thread Starter
Member
Joined: Mar 2012
Posts: 205
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From: Severance, Colorado
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0 litre, line 6
Originally Posted by CCKen
Remove the oil pressure sensor connector (located just behind the distributor). Use a 27 MM deep socket or short open end 27 MM box wrench, or a short 27 MM open end wrench to remove the sensor. Do not use a cresent wrench or pliers to remove the sensor, any shear (side) load on the threaded portion of the sensor may break it if side loaded too much. Hook up an oil pressure test gauge, like in Bbasso's post, start the engine and observe the oil pressure at idle, then at around 1,600 RPM when the engine has come up to operating temperature.
Minimum oil pressure is 13 psi at idle and 37 to 75 psi at 1,600 RPM. 75 psi is the oil pump relief valve setting.
You can borrow (security deposit required) the test gauge kit from auto parts stores like O'reilly or Advance Auto Parts. The oil pressure sensor adaptor on the engine has a 1/8" national Pipe Thread hole for the sensor, so you'll need to select the proper adaptors from the kit to hook up the gauge.
If the oil pressure is wandering around low-high, up to 80 psi at idle the oil pump relief valve MAY be faulty.
Hi guys I have a real quick question on this subject. Did you check your oil pressure gage with out the engine running? Mine did this to me yesterday and so I fused around a little but noticed that key on engine off my gage was showing 38-40 lbs. so I'm wondering is this enough of a indicator that the sending unit is bad?
Herp Derp Jerp

Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
Hi guys I have a real quick question on this subject. Did you check your oil pressure gage with out the engine running? Mine did this to me yesterday and so I fused around a little but noticed that key on engine off my gage was showing 38-40 lbs. so I'm wondering is this enough of a indicator that the sending unit is bad?
Thread Starter
Member
Joined: Mar 2012
Posts: 205
Likes: 0
From: Severance, Colorado
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0 litre, line 6
Originally Posted by salad
Engine needs to be running to develop pressure. Lol
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