pdowty68

How are k&n filters? Waste of $$ or good?

centuryhouse

This is good to hear. My 2000 XJ Sport oil pressure gauge shows around 50 when the rpm is up, but (when hot) drops to 20 in idle. While not as extreme as the OP's, that has had me worried.

BearBrown

Update:

Looks like I will be getting my money back tonight. I was hoping he would have the issue solved by now, but that isn't the case. Good luck to others who have similar issues.

I would still be interested to see a detailed write up for dropping the oil pan. I've tried searching for it but cant seem to find much.

Stovie

I have a 97 ZJ with same problem but mind drops to 0-6 on mechanical gauge once it been up to temp for for a few min at idle then runs around 15-20 at 2krpm has napa gold filter 15w-40 john deere synthetic oil and new Hv pump no top end noise

bigbadon

It is re-assuring to know that there are plenty of 4.0s living and surviving a normal life with low oil pressure. After 40k on mine with similar pressures I believe it is bulletproof.

45shooter

I've had a 2000 XJ for 12 years now and have put 306,000 miles (before I finally killed it through neglect-now has a massive rod knock and sucking coolant) on it and not one peep of an oil pressure problem. Now I get a new 2001 XJ; 147,000 miles and of course nothing on both test drives. 21 miles later in a slowdown in traffic, Check Engine screams at me: 0 pressure on idle. So this thread has definitely helped. Thanks guys.

headRUSH

Save yourself all the trouble and worry and pull the oil pan, get some plastigague and check your bearing clearances. Also check the condition of your bearings while you're at it. If everything checks out and you're still worried about it, put heavier oil in it.

Common issue, don't want to sound bad but after I had this problem 6 months later I was swapping engines.

bigbadon

Mine has been "screaming" at me for 4 years. It used to bother me but now I don't even pay attention to it anymore.

bender32

I have the same problem with my 01. I put 20w50 in it and it solved my problem.... You need an oil that performs better at a higher temp..... Not saying that the 4.0 runs hot but the second number on the oil weight is how the oil handles hot temp so I would recommend 15w50 or 20w50. Worked for me! Good luck

45shooter

Upon further inspection under the hood, it looks as though it's had head work (block still dirty/oily & block clean with visible gasket sealer on head/block & valve cover/head.)

Monetarypollution

I have a 2001 cherokee sport. A couple years back my engine overheated. Following this, I replaced the cooling system with a brand new radiator, thermostat, and hoses. I noticed my oil pressure slowly began to drop to zero when the engine was at running temp while idling. For a short time it didn't seem to drop completely to zero, but eventually it began dropping completely to zero at warm idle, but would rise when I accelerated. I never noticed any loud knocking while this would happen, but still worried about possible damage. In order to prevent damage I would lightly throttle it while holding the brake while stopped at a red light, this way I was able to prevent psi dropping to zero and the "check gauges" light from turning on. First I tried a thicker 50w oil, this defiantly delayed the time and speed for the oil pressure to drop to zero, it wouldn't drop as fast when stopped and took more time after starting the engine for the low pressure problem to begin, but eventually it would still drop to zero at idle, especially on hot days. Next we replaced the sending unit, no luck. Then the oil pump was replaced, no luck. Then After learning about the "0331 Tuppy Head cracking issue", I removed the oil cap and looked down into the top of the engine to discover it was in fact cracked, between cylinders 3 and 4. So I replaced the cracked head with a brand new head I purchased from odessa cylinder(formerly clearwater cylinder), to end up with the same "oil pressure dropping to zero at warm idle" problem. Now recently we began checking bearing clearances, so far all connecting rod bearing clearances are within allowable spec range, clearance on connecting rod bearings 1-6 =(0.002"-0.00175"). Regarding the main bearings(MainBear-1=0.0175") (MB-2=0.0016") (MB-3=0.0015")(MB-4=0.0015")(MB-5=0.0019")(MB-6=0.00175"). So now what?! This is about to send me to the psych tank....Again!!! What else could it be?

Idunno

My 96 and 98 mimic your pressures.