i know every one i have talked to said that its just the xj but when i start my xj the oil pressure is good but then after about ten min it drops to 0 on the gauge and even on the throttle it only reads about 20 i am think the sending unit is bad any other ideas

 

It is always best to "verify" whenever you see low oil pressure.

Get a hold of a mechanical oil pressure gauge. They can be rented very inexpensively from some parts stores; call around.

Temporarily install it where the oil pressure sending unit resides. See what it reads. Then you'll know for sure.

Question for you....you aren't using any anti-freeze are you? You have a 2000 and the 00-01 have the 0331 cylinder head which has a casting defect between cylinders 3-4. Some (not all) will crack and the #1 symptom of a cracked 0331 head is unexplained coolant loss. If the crack isn't caught and resolved (new head) early enough, it can lead to low oil pressure.

 

I have the same issue in mine my gauge stopped working hooked up the aftermarket gauge and worked normal

 

^^ This always one of the first things that you want to do when you have low oil pressure. VERIFY!!!

 

i know to verify already did i work on vehicals for a living and as for the head i am getting a new one lifters are bad and while i have it off might as well put a new head with valves valve springs rocker arms and push rods cause i am loose coolant and had no idea where is was going replaced every thing but the water pump and radiator

 

That isn't good news with that year head.
Get the mech pressure gauge before you spend too much money. If you really have zero oil pressure when it warms up you're probably looking at cam bearings minimum in addition to the head. Some were marginal to begin with and coolant in the oil finishes them off. You might want to weigh that additional expense against that of just replacing the motor.

 

Yep.^^ It's a 2000.......

 

Best advice. Why throw a new head at a practically dead motor.

 

What many people overlook is worn lifter bores. With the head cracking between cylinders 3 & 4 coolant is constantly flowing into the lifter bores on the exhaust side lifters of cylinder 3&4.
There are many stories of people replacing bearings and still puzzled why the oil pressure is still low. Two worn lifter bores will create one hell of a leak! Engine will run fine and possibly run with no problems for a long time. The worn bores can cause the lifters to rock in their bores creating a slight knocking sound at idle that goes away when rpm increases. This can be pinpointed using a stethoscope on the passenger side of the block about one inch below the head gasket.

 

I was told my bearings were shot and I hear slight ticking at idle, I'm doing this asap. thanks.

 

1. Did someone inspect the bearings
2. All 4.0s tick somewhat
3. bearings KNOCK, they don't tick

When head is cracked and leaking the first thing that gets attacked with highly concentrated coolant is the lifter bores as they get filled with coolant, and the cam bearings pick up some of this. The rod and main bearings do not get a high concentration of coolant unless the oil gets severely contaminated. The ticking you hear could be a lifter rocking back and forth in a worn bore.