Oil Pressure Problem

I just bought a 2000 [COLOR=green! important][COLOR=green! important]Jeep [COLOR=green! important]Cherokee[/COLOR][/COLOR][/COLOR] Sport with the 4.0 L Inline 6 Cylinder Automatic 2 Wheel Drive . It has just under 65k miles and seemed to run great while test driving it, however after buying it I started noticing this problem. After looking this up online I found out I am not the only one this has happened to. Read further.

When it warms up a bit and while its at idle it would drop to almost 0 psi of oil pressure and the check gauges light would come on. It had 20W50 oil in it and a Fram filter. My mechanic checked the pressure with a mechanical gauge which was reading exactly the same as the dash and then changed to a better filter and added 10W40. This seemed to help just a little, but not enough to keep it from dropping until the check gauges light came on. I took it back and they ended up installing a high volume oil pump. They also cleaned the pick up screen and tube and said the oil pan was very clean. I drove it for about 15 miles slow and fast, starting and stopping, in a hot South Alabama day and it didn't drop low enough for the light to come on, but it is only running at about 9 psi. I would like to know why it is only running at that level. Any help would be great and I hope I gave enough info.
By the way, the mechanic is a friend of mine and is super honest with everyone he deals with. They are loved by many.

Have you had anyone check the oil pressure sensor? It should be located just above the oil filter, a plug style connector just above it attached to the oil filter adapter. I know when mine went out it was reading all over the place. Try it out cheap and easy to do. 15-20 minutes max. post back and let me know how it turns out.atriot:

You may have a motor that has a cracked head,the coolant mixed with the oil and wiped out the bearings.
This is common on that year vehicle,and you would only notice that the coolant level in the overflow tank was always low or needed to be topped off frequently.
Only cure for the low pressure problem is a new set of bearings.
The change from a 20w oil to a 10 w oil was the wrong way to increase pressure as a 20w is a "thicker" oil.The change from a Fram filter was a good one.
Wayne

Alot of people have pressure issues when using Fram oil filters.

I suggest you try another brand-

Anything but Fram really.

Wayne Sihler said:

You may have a motor that has a cracked head,the coolant mixed with the oil and wiped out the bearings.
This is common on that year vehicle,and you would only notice that the coolant level in the overflow tank was always low or needed to be topped off frequently.
Only cure for the low pressure problem is a new set of bearings.
The change from a 20w oil to a 10 w oil was the wrong way to increase pressure as a 20w is a "thicker" oil.The change from a Fram filter was a good one.
Wayne

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X2^ the high volume pump is a band aid to the bigger problem effective in the short term, but main and rod bearings should be in your plans before you starve the valvetrain and wear even more stuff.

--Shorty

P.S. what color is it?:looney:

I have read that the 2000 year engines had problems with heads that cracked easily. You may want to research that issue and get a carfax history on that Jeep, and check with the dealer as well about any recalls on the heads. That is way too few miles for that low of an oil pressure, especially with 20W50. Don't use fram filters, they are bad news. Stick with K & N, Mobil 1, NAPA gold, or Wix oil filters.

While doing that, replace a quart of oil with Lucas oil additive to get the hot idle oil pressure back up to at least 20 psi. Also if the new filter is Fram replace it immediatly with a quality oil filter brand. On your next oil change try straight 40WT, or 20W50 plus a quart of Lucas.

phrenic13 said:

I just bought a 2000 [COLOR=green! important][COLOR=green! important]Jeep [COLOR=green! important]Cherokee[/color][/color][/color] Sport with the 4.0 L Inline 6 Cylinder Automatic 2 Wheel Drive . It has just under 65k miles and seemed to run great while test driving it, however after buying it I started noticing this problem. After looking this up online I found out I am not the only one this has happened to. Read further.

When it warms up a bit and while its at idle it would drop to almost 0 psi of oil pressure and the check gauges light would come on. It had 20W50 oil in it and a Fram filter. My mechanic checked the pressure with a mechanical gauge which was reading exactly the same as the dash and then changed to a better filter and added 10W40. This seemed to help just a little, but not enough to keep it from dropping until the check gauges light came on. I took it back and they ended up installing a high volume oil pump. They also cleaned the pick up screen and tube and said the oil pan was very clean. I drove it for about 15 miles slow and fast, starting and stopping, in a hot South Alabama day and it didn't drop low enough for the light to come on, but it is only running at about 9 psi. I would like to know why it is only running at that level. Any help would be great and I hope I gave enough info.
By the way, the mechanic is a friend of mine and is super honest with everyone he deals with. They are loved by many.

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I'd say swap out the Fram filter first, put in a half quart of oil after swapping the filter (if you aren't doing a full oil change)

THEN tell us what the oil pressure readings are!

Blaine B. said:

I'd say swap out the Fram filter first, put in a half quart of oil after swapping the filter (if you aren't doing a full oil change)

THEN tell us what the oil pressure readings are!

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Better yet, just get rid of the Fram, if the new one is a Fram (?), replace it with one of the recomended filters below, then re-test the hot oil idle pressure. Then if the hot idle oil presure is not at least 20 psi, then add the Lucas and retest it.

He just changed his oil, so no need to change it yet. It would be interested if he documented a low oil pressure caused by a NEW Fram filter! and not just a well used one.

I suspect he may have bought a Jeep that already had a cracked head issue that diluted the oil and caused premature bearing wear before he bought it. But since many have had oil pressure problems with Fram filters, he should check the filter possibility first.

If it is not the filter, just raise the oil viscosity until you get 20 psi minimum hot oil at idle pressure. Then you might want to trade it for better year Jeep. 2000 was the worst year engine wise for a 4.0 engine. The other years have typically lasted 300,000 miles before a rebuild, and not to blow smoke, but one guy in this forum was still running his old 4.0 with something like 80 Wt gear oil , and who knows how many miles on it. I think he said he was running straight Lucas additive.

If you decide to keep it and the engine does not last, I would get a JY (junk Yard) 4.0 pull from a low mileage, less than 100 K, late 97, 98 or 99 XJ (for like $100) that was wrecked and get your mechanic friend to help you swap the engines, rather than try rebuilding it.

phrenic13 said:

I just bought a 2000 [COLOR=green! important][COLOR=green! important]Jeep [COLOR=green! important]Cherokee[/COLOR][/COLOR][/COLOR] Sport with the 4.0 L Inline 6 Cylinder Automatic 2 Wheel Drive . It has just under 65k miles and seemed to run great while test driving it, however after buying it I started noticing this problem. After looking this up online I found out I am not the only one this has happened to. Read further.

When it warms up a bit and while its at idle it would drop to almost 0 psi of oil pressure and the check gauges light would come on. It had 20W50 oil in it and a Fram filter. My mechanic checked the pressure with a mechanical gauge which was reading exactly the same as the dash and then changed to a better filter and added 10W40. This seemed to help just a little, but not enough to keep it from dropping until the check gauges light came on. I took it back and they ended up installing a high volume oil pump. They also cleaned the pick up screen and tube and said the oil pan was very clean. I drove it for about 15 miles slow and fast, starting and stopping, in a hot South Alabama day and it didn't drop low enough for the light to come on, but it is only running at about 9 psi. I would like to know why it is only running at that level. Any help would be great and I hope I gave enough info.
By the way, the mechanic is a friend of mine and is super honest with everyone he deals with. They are loved by many.

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That sucks. You are screwed...as is my XJ. I have the same problem, I spent months and lots of $ trying to track down why i have low oil pressure. Looking to do an engine swap as soon as i get the $.