Oil Pressure: How low is too low?
01-18-2012, 01:13 AM
#1
Seasoned Member
Thread Starter
Join Date: Dec 2011
Location: Wenatchee, WA
Posts: 319
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1990
Model: Cherokee
Engine: 4.0L Renix
Oil Pressure: How low is too low?
At idle (500-800 rpms) when my engines warm my oil pressure is at the mark between the bottom and the 40 I believe. It recently started happening. Checked my oil level and it's full. Pressure is normal upon cold start. No engine knocking.
01-18-2012, 02:57 AM
#2
Member
Join Date: Jan 2012
Location: Texas
Posts: 124
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1995
Model: Cherokee
Engine: 4.0
If your oil pressure falls below 10 p.s.i. at idle, you have a problem that could result in engine damage. Normal oil pressure is 30 p.s.i. (+/- 5 p.s.i.). There's a lot of things that could cause low oil pressure, but starting with the most obvious things first:
1.) Is there oil in the engine? Is it up to the "Full" mark on the dipstick? (This is sort of a "duh" question.)
2.) How often has the oil/filter been changed? (I change my oil every 3,500 miles, and the filter every 7,000.) If the oil is black and dirty, then check for sludge/ ash in the valve cover valley. Pull the valve cover. Any crap deposited everywhere? If yes, you are going to need to drop the pan too, and chip every bit of crap out of your engine with a screwdriver, etc.. Vacuum out all the junk with a shop vac. You don't want all that dirt and crap cycling through your oil pump. Check and clean the oil pump screen. Replace it if it's all crudded up.
3.)Once the oil is clean & new, and the oil filter replaced, fire up the engine cold and rev it up like to 2,000 rpm. Any noise? Bearing clatter? What does the oil pressure look like cold? Pop the hood, and with the engine running pull the oil filler cap and look to see if you've got oil being pumped to the head. (You might need a flashlight.) If you don't have oil running in the bottom of the cylinder head valley, I'd say you have oil pump problems.
4.) Screw an external (mechanical) oil gauge into the oil pressure sender hole, start the engine cold and compare the oil pressure as it warms up. If it starts low and stays low, the problem is probably the oil pump. (Replace the screen and pump, check it all again.) If it starts high, but falls as the engine heats up, and winds up being zero or close to it, then it's probably the crankshaft/ bearings ($$$orry, bro.) If it starts out at 30-35 and drops to maybe 10 or so when it's warm, it's probably the sending unit. (They're cheap-- $20 from Quadratec. Replace it.)
If none of that stuff tells you anything, you need somebody smarter than me answering your posts!
1.) Is there oil in the engine? Is it up to the "Full" mark on the dipstick? (This is sort of a "duh" question.)
2.) How often has the oil/filter been changed? (I change my oil every 3,500 miles, and the filter every 7,000.) If the oil is black and dirty, then check for sludge/ ash in the valve cover valley. Pull the valve cover. Any crap deposited everywhere? If yes, you are going to need to drop the pan too, and chip every bit of crap out of your engine with a screwdriver, etc.. Vacuum out all the junk with a shop vac. You don't want all that dirt and crap cycling through your oil pump. Check and clean the oil pump screen. Replace it if it's all crudded up.
3.)Once the oil is clean & new, and the oil filter replaced, fire up the engine cold and rev it up like to 2,000 rpm. Any noise? Bearing clatter? What does the oil pressure look like cold? Pop the hood, and with the engine running pull the oil filler cap and look to see if you've got oil being pumped to the head. (You might need a flashlight.) If you don't have oil running in the bottom of the cylinder head valley, I'd say you have oil pump problems.
4.) Screw an external (mechanical) oil gauge into the oil pressure sender hole, start the engine cold and compare the oil pressure as it warms up. If it starts low and stays low, the problem is probably the oil pump. (Replace the screen and pump, check it all again.) If it starts high, but falls as the engine heats up, and winds up being zero or close to it, then it's probably the crankshaft/ bearings ($$$orry, bro.) If it starts out at 30-35 and drops to maybe 10 or so when it's warm, it's probably the sending unit. (They're cheap-- $20 from Quadratec. Replace it.)
If none of that stuff tells you anything, you need somebody smarter than me answering your posts!
Last edited by Low Profile; 01-18-2012 at 03:01 AM.
01-18-2012, 05:30 AM
#3
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,867
Received 1,524 Likes
on
1,236 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Clean the electrical connector at the sender real well. Does it have oil on/in it?
What brand of oil filter are you using?
What brand of oil filter are you using?
01-18-2012, 05:43 AM
#4
CF Veteran
Join Date: Nov 2010
Location: In the middle of Minnesota!
Posts: 5,804
Received 99 Likes
on
88 Posts
Year: 1999
Model: Cherokee
Engine: 4.0
Oil pressure spec. for the Jeep 4.0 is this:
*Not less than 13 psi at HOT idle
*Between 37-75 psi over 1600 rpms
If you're in this zone, you're fine. If you're not, you should verify it with a MECHANICAL gauge as you could have a faulty sending unit, inaccuracy between the sending unit and the gauge, etc.
*Not less than 13 psi at HOT idle
*Between 37-75 psi over 1600 rpms
If you're in this zone, you're fine. If you're not, you should verify it with a MECHANICAL gauge as you could have a faulty sending unit, inaccuracy between the sending unit and the gauge, etc.
01-18-2012, 01:53 PM
#6
Seasoned Member
Thread Starter
Join Date: Dec 2011
Location: Wenatchee, WA
Posts: 319
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1990
Model: Cherokee
Engine: 4.0L Renix
01-18-2012, 01:54 PM
#7
Seasoned Member
Thread Starter
Join Date: Dec 2011
Location: Wenatchee, WA
Posts: 319
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1990
Model: Cherokee
Engine: 4.0L Renix
Oil pressure spec. for the Jeep 4.0 is this:
*Not less than 13 psi at HOT idle
*Between 37-75 psi over 1600 rpms
If you're in this zone, you're fine. If you're not, you should verify it with a MECHANICAL gauge as you could have a faulty sending unit, inaccuracy between the sending unit and the gauge, etc.
*Not less than 13 psi at HOT idle
*Between 37-75 psi over 1600 rpms
If you're in this zone, you're fine. If you're not, you should verify it with a MECHANICAL gauge as you could have a faulty sending unit, inaccuracy between the sending unit and the gauge, etc.
Trending Topics
01-18-2012, 01:54 PM
#8
Seasoned Member
Thread Starter
Join Date: Dec 2011
Location: Wenatchee, WA
Posts: 319
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1990
Model: Cherokee
Engine: 4.0L Renix
01-18-2012, 01:55 PM
#9
Seasoned Member
Thread Starter
Join Date: Dec 2011
Location: Wenatchee, WA
Posts: 319
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1990
Model: Cherokee
Engine: 4.0L Renix
If your oil pressure falls below 10 p.s.i. at idle, you have a problem that could result in engine damage. Normal oil pressure is 30 p.s.i. (+/- 5 p.s.i.). There's a lot of things that could cause low oil pressure, but starting with the most obvious things first:
1.) Is there oil in the engine? Is it up to the "Full" mark on the dipstick? (This is sort of a "duh" question.)
2.) How often has the oil/filter been changed? (I change my oil every 3,500 miles, and the filter every 7,000.) If the oil is black and dirty, then check for sludge/ ash in the valve cover valley. Pull the valve cover. Any crap deposited everywhere? If yes, you are going to need to drop the pan too, and chip every bit of crap out of your engine with a screwdriver, etc.. Vacuum out all the junk with a shop vac. You don't want all that dirt and crap cycling through your oil pump. Check and clean the oil pump screen. Replace it if it's all crudded up.
3.)Once the oil is clean & new, and the oil filter replaced, fire up the engine cold and rev it up like to 2,000 rpm. Any noise? Bearing clatter? What does the oil pressure look like cold? Pop the hood, and with the engine running pull the oil filler cap and look to see if you've got oil being pumped to the head. (You might need a flashlight.) If you don't have oil running in the bottom of the cylinder head valley, I'd say you have oil pump problems.
4.) Screw an external (mechanical) oil gauge into the oil pressure sender hole, start the engine cold and compare the oil pressure as it warms up. If it starts low and stays low, the problem is probably the oil pump. (Replace the screen and pump, check it all again.) If it starts high, but falls as the engine heats up, and winds up being zero or close to it, then it's probably the crankshaft/ bearings ($$$orry, bro.) If it starts out at 30-35 and drops to maybe 10 or so when it's warm, it's probably the sending unit. (They're cheap-- $20 from Quadratec. Replace it.)
If none of that stuff tells you anything, you need somebody smarter than me answering your posts!
1.) Is there oil in the engine? Is it up to the "Full" mark on the dipstick? (This is sort of a "duh" question.)
2.) How often has the oil/filter been changed? (I change my oil every 3,500 miles, and the filter every 7,000.) If the oil is black and dirty, then check for sludge/ ash in the valve cover valley. Pull the valve cover. Any crap deposited everywhere? If yes, you are going to need to drop the pan too, and chip every bit of crap out of your engine with a screwdriver, etc.. Vacuum out all the junk with a shop vac. You don't want all that dirt and crap cycling through your oil pump. Check and clean the oil pump screen. Replace it if it's all crudded up.
3.)Once the oil is clean & new, and the oil filter replaced, fire up the engine cold and rev it up like to 2,000 rpm. Any noise? Bearing clatter? What does the oil pressure look like cold? Pop the hood, and with the engine running pull the oil filler cap and look to see if you've got oil being pumped to the head. (You might need a flashlight.) If you don't have oil running in the bottom of the cylinder head valley, I'd say you have oil pump problems.
4.) Screw an external (mechanical) oil gauge into the oil pressure sender hole, start the engine cold and compare the oil pressure as it warms up. If it starts low and stays low, the problem is probably the oil pump. (Replace the screen and pump, check it all again.) If it starts high, but falls as the engine heats up, and winds up being zero or close to it, then it's probably the crankshaft/ bearings ($$$orry, bro.) If it starts out at 30-35 and drops to maybe 10 or so when it's warm, it's probably the sending unit. (They're cheap-- $20 from Quadratec. Replace it.)
If none of that stuff tells you anything, you need somebody smarter than me answering your posts!
01-19-2012, 03:29 AM
#10
Senior Member
Join Date: Sep 2008
Location: Sioux Falls, SD
Posts: 897
Likes: 0
Received 12 Likes
on
9 Posts
Year: 1999
Model: Cherokee(XJ)
Engine: 4.0L
Im sittin at about 5 PSI hot at idle and about 19 on the interstate. Installed a new Mellnig MV pump last year to no avail. 250K on the engine. Seems to run ok tho. I keep the oil changes to 5K. Just waiting for her to explode tho.
Still pull those 900 mile trips to Northern Minnesota during the winter just fine.
Still pull those 900 mile trips to Northern Minnesota during the winter just fine.
01-19-2012, 05:29 AM
#11
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,867
Received 1,524 Likes
on
1,236 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
diskman, here's an interesting read on oil pressure:
http://www.jeepforum.com/forum/f19/4...fixed-1304679/
http://www.jeepforum.com/forum/f19/4...fixed-1304679/
01-19-2012, 09:27 AM
#12
Seasoned Member
Thread Starter
Join Date: Dec 2011
Location: Wenatchee, WA
Posts: 319
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1990
Model: Cherokee
Engine: 4.0L Renix
Im sittin at about 5 PSI hot at idle and about 19 on the interstate. Installed a new Mellnig MV pump last year to no avail. 250K on the engine. Seems to run ok tho. I keep the oil changes to 5K. Just waiting for her to explode tho.
Still pull those 900 mile trips to Northern Minnesota during the winter just fine.
Still pull those 900 mile trips to Northern Minnesota during the winter just fine.
01-21-2012, 02:06 AM
#14
CF Veteran
Join Date: May 2010
Location: Fort Collins, CO
Posts: 3,405
Likes: 0
Received 2 Likes
on
2 Posts
Year: 1996
Model: Cherokee
Engine: 4.0L HO
Most recent oil change I started running 10-30 Rotella-T Diesel engine oil. Even hot, above 1200 RPM its just barely below 80 and idle barely below 40.
Running regular cheap oil it would usually be a bit under 60 above 1200 and about 30 idle. Always use Wix filters.
Running regular cheap oil it would usually be a bit under 60 above 1200 and about 30 idle. Always use Wix filters.
02-19-2024, 10:23 AM
#15
Newbie
Join Date: Feb 2024
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
If your oil pressure falls below 10 p.s.i. at idle, you have a problem that could result in engine damage. Normal oil pressure is 30 p.s.i. (+/- 5 p.s.i.). There's a lot of things that could cause low oil pressure, but starting with the most obvious things first:
1.) Is there oil in the engine? Is it up to the "Full" mark on the dipstick? (This is sort of a "duh" question.)
2.) How often has the oil/filter been changed? (I change my oil every 3,500 miles, and the filter every 7,000.) If the oil is black and dirty, then check for sludge/ ash in the valve cover valley. Pull the valve cover. Any crap deposited everywhere? If yes, you are going to need to drop the pan too, and chip every bit of crap out of your engine with a screwdriver, etc.. Vacuum out all the junk with a shop vac. You don't want all that dirt and crap cycling through your oil pump. Check and clean the oil pump screen. Replace it if it's all crudded up.
3.)Once the oil is clean & new, and the oil filter replaced, fire up the engine cold and rev it up like to 2,000 rpm. Any noise? Bearing clatter? What does the oil pressure look like cold? Pop the hood, and with the engine running pull the oil filler cap and look to see if you've got oil being pumped to the head. (You might need a flashlight.) If you don't have oil running in the bottom of the cylinder head valley, I'd say you have oil pump problems.
4.) Screw an external (mechanical) oil gauge into the oil pressure sender hole, start the engine cold and compare the oil pressure as it warms up. If it starts low and stays low, the problem is probably the oil pump. (Replace the screen and pump, check it all again.) If it starts high, but falls as the engine heats up, and winds up being zero or close to it, then it's probably the crankshaft/ bearings ($$$orry, bro.) If it starts out at 30-35 and drops to maybe 10 or so when it's warm, it's probably the sending unit. (They're cheap-- $20 from Quadratec. Replace it.)
If none of that stuff tells you anything, you need somebody smarter than me answering your posts!
1.) Is there oil in the engine? Is it up to the "Full" mark on the dipstick? (This is sort of a "duh" question.)
2.) How often has the oil/filter been changed? (I change my oil every 3,500 miles, and the filter every 7,000.) If the oil is black and dirty, then check for sludge/ ash in the valve cover valley. Pull the valve cover. Any crap deposited everywhere? If yes, you are going to need to drop the pan too, and chip every bit of crap out of your engine with a screwdriver, etc.. Vacuum out all the junk with a shop vac. You don't want all that dirt and crap cycling through your oil pump. Check and clean the oil pump screen. Replace it if it's all crudded up.
3.)Once the oil is clean & new, and the oil filter replaced, fire up the engine cold and rev it up like to 2,000 rpm. Any noise? Bearing clatter? What does the oil pressure look like cold? Pop the hood, and with the engine running pull the oil filler cap and look to see if you've got oil being pumped to the head. (You might need a flashlight.) If you don't have oil running in the bottom of the cylinder head valley, I'd say you have oil pump problems.
4.) Screw an external (mechanical) oil gauge into the oil pressure sender hole, start the engine cold and compare the oil pressure as it warms up. If it starts low and stays low, the problem is probably the oil pump. (Replace the screen and pump, check it all again.) If it starts high, but falls as the engine heats up, and winds up being zero or close to it, then it's probably the crankshaft/ bearings ($$$orry, bro.) If it starts out at 30-35 and drops to maybe 10 or so when it's warm, it's probably the sending unit. (They're cheap-- $20 from Quadratec. Replace it.)
If none of that stuff tells you anything, you need somebody smarter than me answering your posts!
as per chrysler service information minimum oil pressure is 4 psi at warm idle. and 25-80 psi at 3000 rpm.