I just purchased a 1999 Cherokee Sport 4.0 with 126,000 miles.When changing the engine oil I noticed something very strange. The oil level before draining was in the safe range but only 4 quarts came out. I then added 5 quarts with a new Mopar filter.When I started it up the oil pressure was about 50 psi. However the oil level on the dipstck was about 3/8ths of an inch above the max mark on the dipstick. Since all the specs for the 4.0 call for 6 quarts of oil I decided to add another 1/2 quart for a total of 5 1/2 quarts.The level on the dipstick at this point is more than a 1/2 inch above the max mark. When I started it up again there was no oil pressure and the check engine light came on.I ran it for about 20 seconds before I shut it down.These were symptoms of too much oil in the pan. I drained out about a quart and I'm back to 50 psi and no check engine light. Level at this point is right on max.
I am totally stumped.If it had the wrong dipstick then it would not have lost oil pressue at 5 1/2 quarts. If it had a layer of sludge in the oil pan then I would also see sludge in the rocker arm assembly.I can see through the oil fill hole on the valve cover that there is no sludge. My only guess is that the oil pan was damaged and then replaced with a lower capacity pan.
I am looking for any answers to this mystery.
Thanks for any insight

 

It should hold six quarts. I would pull the valve cover and see if the top end is sludged up, if it is I would then pull the pan and see how much crap is in the pan. How did the oil that was drained out look?

 

You're basically saying your pan is full @ 4Qts?

I don't know if a lower capacity oil pan would even fit the bolt pattern on that 4.0L I6 without tapping new holes... Maybe there could be a pan out there somewhere?

Also, are you sure you didn't purchase a 2.5L engine? Or possibly the engine was swapped for a 2.5L?


Having 2 full quarts of sludge sounds a little extreme doesn't it?

 

I can see that the top end is clean.

 

The engine is definitely the 4.0l 6 cyl.

 

Oil level will not affect pressure. You've got more than one thing going on here. The 4.0 holds 6 quarts of oil.

Possibly you've got the wrong dipstick?

Also, what brand of oil filter did you use?

You sure you didn't accidentally whack the oil sending unit when removing the filter?

 

Always check oil level with a cold engine.....i usually do it in the morning.

GL.