Jeep Oil Pressure

[rheagler]

I have a 2001 Jeep Cherokee 4.0 6cyl that I bought new. It has 87000 miles on it and I have never had a serious problem with it. I usually change the oil and filter every 3500 miles, but on occaision I have stretched it to 5000. Recently after driving for 30 minutes or more at normal highway speeds (60-70), and then stopping for a traffic light, tollbooth (NJ) or whatever reason, the oil pressure has been known to drop down low enough for the "check guages" light to come on. I took it back to where I have been having the oil changed and they tested the guage and sending unit. Sure enough the guage and sending unit are fine, the pressure drops to 9 psi at idle. It should be 13. Low and behold, I find out they have been using 5W30 in the car instead of 10W30. Oil was changed back to 10W30, all was good for about 300 miles, now the same thing is happening. Could a switch to synthetic help to boost the pressure? Could it just be the oil pump or could I have spent bearings? Are these questions too vague? I really hate to think that the thinner oil could make that much of a difference, but could it?

 

[rwise]

Re: Jeep Oil Pressure

A bad or poor quality (can you say fram) oil filter can do this also, I run the Napa gold filters. There has been much chat bout filters here in the past. Other things can be the filter screen is stopping up, oil pump failing. I do not think changing (with 87k miles) to synth oil will help, and it may hurt.

 

[beerfilter]

Re: Jeep Oil Pressure

As RWISE pointed out , it could be any number of problems .
Your best bet is to just go ahead and drop the oil pan , before you completely spin your bearings , replace the oil pump , and , inspect your main bearings for wear .

Do not try to much "try this and see what happens" , as what WILL eventually happen is you popping for a reman engine !

My father had this same problem with his 95 Ford .
While limping it to the mechanic , the oil pump failed completely a couple miles from the shop .
He now has a reman 5.8L , for several thousand more dollars than the cost of an oil pump .
Procrastination can be very expensive .

IMO , your bearings are probably fine , as these 4.0L's are extremely rugged units .
A replacement pump and pan gasket set can be found at most any parts store , or , you can order online from several reputable sites .
Should set you back ~ $90 for the pump , ~$30 for the pan gasket .
Even with shop labor , this is WAY cheaper than a tow and a rebuild/reman engine .

HTH

 

[ezbtr]

Re: Jeep Oil Pressure

I had a 92 w/ the same motor, was very well taken care of, I used Redline full synthetic 10/40 from 120K in it til I gave it to my daughter w/ 175K on it - ran PERFECT. I noticed when using 10/30 oil pressure was lower like 15 PSI at idle, went to 10/40 and went up to about 20. I don't think 5/30 would hurt that motor and you've changed oil at regular intervals so clogged screen shouldnt be an issue w 87K on it. Those motors and trannys are the best. You SHOULDN'T need to replace oil pump unless it was defective, or yeah maybe unless a bad oil filter did your pump in. So maybe your pump does need replacing - just wayyyyyyyy to early in that motor's life!

 

[rheagler]

Re: Jeep Oil Pressure

Thanks for all the input.
I do know that the RIGHT thing to do is drop the pan and inspect the bearings and replace the pump, I guess I am just in denial that the pump could be bad. The engine has no knocks or thumps that would indicate a bad bearing. It just does seem way too early in this engines life to need a rebuild.
Just out of curiosity, what damage could occur by switching to synthetic oil at this stage of the game?
At the very least I am going to change the oil again and use an OEM or better filter. If there is no change, I'll drop the pan.
Thanks again for the input.

 

[PW2]

Re: Jeep Oil Pressure

I have that same engine, only a 2000 model with 113 k miles.

It always runs with 40+# pressure, no less than 35# when hot at idle.

I use 10W30--sometimes synthetic, sometimes the high mileage variety--set the computer to tell me @3000 miles--and never go beyond 3500.

It never needs any add oils between changes.

 

[_brad_]

Re: Jeep Oil Pressure

I have a 88 4.0 with 130,xxx and have the same problem. I found that running 20x50 in summer and 10x30 in winter really helps (I'm in MN).

With an engine this old, you can rest assured seals, gaskets, cylinders, rings and the like are either worn, brittle, cracked, scored or otherwise not sealing like they should. I have found a thicker oil not only cuts down on friction and heat, but can also up compression numbers.

I use 20x50 in my 82 motorcycle, my 84 Yamaha three wheeler, and anything with signs of low compressions/worn rings.

My 2 cents.

 

[rwise]

Re: Jeep Oil Pressure

when I changed to synth oil in my old truck, the front and rear seals started pouring oil out. Yes they were old and dry to start with, but were not leaking before. If the seals are in good shape you should have no problem changing to synth oil.

 

[MikDee]

Re: Jeep Oil Pressure

IMO, It doesn't matter if it's synthetic, or not, it's not going to help, but not hurt either. I use synthetic blend it's cheaper, and still gives you the side benefits of smoother, cooler running, more power, and better gas milage, I suggest 10/40W oil either way, you can also use 20/50W in the summer.