Oil Pressure issues/question

My buddy has a 2000 XJ that 31000 miles on it. The lady who had the Jeep before him replaced the oil according to mileage but not based on date (clearly not as much as needed since its a 2000 with 31000 miles). Oil pan removed with a ton of sludge. Cleaned out the pan, replaced oil pump the oil filter arm/attatchment point, sending unit, radiator flushed and new hoses installed.

On a cold start it runs at 45 psi but once its warm it runs at about 7 psi when at idle after warmed up but between 25-35 psi on the interstate. There's no pinging, no smoke, no smells, running in a good temp range. Any input on what to expect? Even though the Jeep isnt showing any symptoms as of now, he was concerned that the PSI was too low.

StrizzyChris said:

My buddy has a 2000 XJ that 31000 miles on it. The lady who had the Jeep before him replaced the oil according to mileage but not based on date (clearly not as much as needed since its a 2000 with 31000 miles). Oil pan removed with a ton of sludge. Cleaned out the pan, replaced oil pump the oil filter arm/attatchment point, sending unit, radiator flushed and new hoses installed.

On a cold start it runs at 45 psi but once its warm it runs at about 7 psi when at idle after warmed up but between 25-35 psi on the interstate. There's no pinging, no smoke, no smells, running in a good temp range. Any input on what to expect? Even though the Jeep isnt showing any symptoms as of now, he was concerned that the PSI was too low.

Click to expand...

I have seen a oil press drop of this much many times.

Is the low oil press warning light coming on at all?

Here is a fix that someone else did on a 2002 4L

I dug around and found an old mechanical oil pressure gauge and installed it and left it hanging in the engine compartment. Showed same as the dash gauge - low pressure, about 8-10 psi at idle and rising to 55-60 at 2500 rpm. I let it idle for a while but heard no odd noises. Just the same as before - good pressure on cold start and decreasing as engine warms. Went back and searched some more and found info about the oil gallery behind the sending unit getting clogged with sludge. So I took off the mechanical gauge and left the brass adapter in the hole and stuck a short piece of rubber hose to that and into a drain pan. I then turned it on and revved it at 4000 for about 8 seconds and shut it off. I checked the drain pan and found some obvious bits of sludge that had been blown out. I connected the mech gauge again and topped off the oil. Turned it back on and problem solved! Pressure at idle now 18-20 psi and 60 psi at 2500. Replaced original sender and dash gauge was back to normal. Hope this helps someone with the same problem

that sounds exaclty like the symptoms he mentioned to me. no knocking, no symtpoms at all. PSI exactly the same at same moments. starts great, once warm drops but is good when at higher rpms on roadways. Ill pass on the info and hopefully it works out for him :thumb: :drinks: