I always get so much info from everyone on the forum. My wife's 2001 Cherokee oil pressure gauge will drop all the way down and check gauges light comes on when at an idol. Fine when driving. Oil amount is perfect. Could this be the oil pressure switch or oil pump?

 

Definitely try the sending unit (switch) first. Also, you could remove it and temporarily put a mechanical gauge in it's place, to verify.

 

Check oil presure with mechanical gauge if it agrees with the dash gauge you know the problem is low presure.Replace the oil pump with a high volume pump, it should about double your oil presure hot.

 

^^ While you have the pressure sender off, clean out the small oil passage that feeds it. Some other members have reported the same symptoms as you due to a partially clogged passage.

 

Thanks. I will definitely try the pressure switch first.

 

1. Either test with a mechanical gauge or swap in a new oil pressure sending unit. Get a MOPAR unit from Jeep for the best reliability/accuracy/mating with your factory gauge. Aftermarket sending units have not shown to be great for making the long haul.

2. Here is the link to the clogged orifice issue. Not common, but it can happen.

http://www.jeepforum.com/forum/f19/4...fixed-1304679/

 

Um, have you had any other trouble, such as loss of coolant without evidence of where it's going?

 

I'm gonna try this. I'm having the same problem. But my pressure isn't dropping to low yet

 

^^^^^A+++^^^^
If it makes you feel better mine has the same symptoms and I have been driving it that way for a long time. Do a google search on this and you will see this is a common complaint with the 2000-2001 4.0 engine. Some caused by the cracked head BUT alot for no apparent reason. There have been 4.0s that have made it to 300k with low oil pressure!
I have read of cases where people have replaced pumps,bearings or completely rebuilt the engine and still ended up with low pressure.
I quit worrying about mine long ago...it ain’t knocking so I'll keep rock'in.

 

Another good point...

If you are using coolant and can't find the leak, it is not impossible that you have a cracked 0331 cylinder head. The #1 symptom of a cracked 0331 is "unexplained coolant loss"

And if that crack is left long enough, the coolant mixing with the oil will toast your engine bearings. And that means "low oil pressure".

Not saying that is your issue, but it is a possibility if you are having to add coolant to your reservoir.

 

I also have an '01 with low oil pressure at idol and I lose a lot of coolant and dont know where its going. I fill the reservoir and a week or two later its close to empty... When the oil is changed, wouldnt you be able to tell that there is coolant in it? Wouldnt it be milky or something on the dipstick?

 

How long have you had low oil pressure? How long have you been losing coolant?
I would think that if that much coolant was in the oil it would be obvious. A simple test would be to pull the dipstick after motor reaches operating temperature and drip it onto the exhaust manifold. If it has water in it it will sizzle.

 

Sometimes you can have milky oil, but other times not. It is not a reliable indicator.

As you have an 01 and you are using lots of coolant, you're either "leaking it" or you're "burning it".

Have you performed a comprehensive search for a leak by getting underneath your XJ with a good light? If you absolutely cannot find a leak, sorry to be the bearer of bad news but the odds then would be high that you have a cracked cylinder head. Not that uncommon for the 00-01.

 

My jeep did this too the sender itself had oil in the connector.
Replaced sender no more issue . I had previously been into the motor so my worries of catastrophic issues were a non issue .