YoTeach

Hello everyone, i just bought a 2001 Cherokee sport a few weeks ago after being jeepless for a few months. It's in amazing condition with 140,000 miles, auto trans and 8.25 rear axle.

When I bought the xj the oil pressure gauge was maxed at 80 so I was curious to see what was the actual psi. After plugging it all up and running it, it read 13 psi at idle and around 30-40 when giving gas.

I thought it was fuel pump but my friend keeps mentioning a cracked head or something...


Thanks

Cheddarnut

Try the sending unit. Also, on the cracked block question. There is a test shops can do to test for coolant in the oil. You can also send a sample out to these guys:

http://www.blackstone-labs.com/



http://www.partsgeek.com/gbproducts/...FSNk7AodsS0A2Q

YoTeach

Yeah I tried a new pressure switch and it read zero at idle but 30 at driving. I put a mechanical gauge on it and it read 12-14 at idle

bryweb

To research the head, research/Google "Jeep 0331 Cracked Head" and you will have a ton of reading on the cracked head.

The crack can sometimes be seen through the oil fill cap between cylinder 3&4, not all crack, but many do, if you drive it for a couple of weeks and it uses no coolant then you are probably good to go. just try not to overheat the motor or you have a good chance to crack the head.

If your manual gauge reads over 10lbs at Idle AFTER THE JEEP OIL IS HOT (Not the Coolent Temp Guage so drive 15-30 minutes after coolant is at 210 degrees) you are good to go. I have replaced bad 0331 heads only to find out the leaking coolent took out the cam bearings and screwed my oil pressure, so I had to tear the motor down and had to replace those bearings after putting a new head on.... this is why I know the motor oil needs to get hot to check the pressure (I tried a high volume pump and thicker oil before giving up and replacing the cam bearings.)

I hope this helps.

Bryan

JPXJMOAB

The XJ has a minimum spec of 13 at idle according to Chrysler spec.. It should run between 35-50. I know mine runs at 40 at about 2k RPM.

bryweb

I still would not worry about it if it was over 10psi at idle when hot and 30-40psi driving down the road.

Its a jeep 4.0L, it can take it !!!!!!

bigbadon

2000 & 2001 had issues other than cracked heads that cause low oil pressure. Cam bearings walking out of its journal is one of them. If motor is not making noise this is a likely possibility...especially if you find shiny dust like specks when you change oil.

Fred/N0AZZ

Good point!


This will be even more apparent if you cut the filter open and unroll the material (if its a good quality one (NAPA Gold/WIX) there will a bunch of them. But they will be in the oil also when you drain it if you look at it in the pan.

YoTeach

Yeah after running down the street and then checking it'll read 12-14 psi and it'll jump to over 30 psi.

Mine doesn't make any noises other than the normal sounds lol

erykv1

I believe the general rule of thumb is 10 psi of oil pressure per 1k RPM for adequate lubrication.

bigbadon

Actually that is a general rule for determining engine condition NOT lubrication. Pressure is not a function, rather it is a result of clearances
being small enough to create oil restriction.