Fellas - Quick question. I have had my 2001 Jeep XJ (4.0) since March and in that time have fixed the leaking oil from the RMS, valve cover, and oil filter adapter, along with too many other things to count.

When I replaced the RMS I of course put on a new oil pan gasket. For about the last 3 weeks the front of the pan has developed a slow leak where I applied RTV to the bell housing area (this is just below the pulley - the lowest point on the oil pan). Not a huge leak, a drip or two every 24-48 hours.

I have driven the Jeep for the last several weeks off and on (it's not a DD) including a 300 mile round trip to the mountains and back. I have driven the Jeep the last three days where temps were above 40* and have had no issues.

This morning I drove the Jeep to work and temps were in the low 30* temps. Once the engine heated up, at stops, the oil pressure dummy gauge on the dash dropped to zero and the "check gauges" light came on.

What is the most likely culprit of this given the fact it has been running fine up until this cold day? A couple ideas based on reading this morning are below:

>Fix the oil leak by dropping oil pan and replacing gasket? Could that be causing the problem? Seems to have been running fine otherwise.
>While I was down there I would replace the oil pump.
>Replace the oil pressure sending unit (may try this first since it is easy)
>Clean electrical connectors on oil sending unit which have likely built up sludge over the years (might try this first since it is easy)
>Replace FRAM oil filter with a WIX or NAPA Gold filter
>Worst case there has been mention of the 0331 head crack but I have not been losing coolant and the oil level seems fine

 

You say that the gauge says it dropped to zero but did you hear it start to knock? If it was truly at 0 you would hear it for sure.I say check your oil pressure with a mechanical gauge if you hear no knock.

 

Thanks - no change in engine performance - continued to run just fine. Apparently this is a common problem when the oil pressure sending unit (located near the oil filter) goes or starts to go bad. I am going to start with replacing that and will post up if this solves my problem.

 

I would still check it with a mechanical gauge while your at it just so you will know if your gauge reads right or if its off some after you change the psu.

 

While you have the oil pressure sending unit out, clean the opening out with a pipecleaner or small bore barrel brush. This did not work in my case (same symptoms after replacing VC gasket), but I have seen many threads where it has worked for others.

 

Thank you! I was trying to figure out what others were referring to with the pipe cleaner method. I will give that a go as well.

 

The connector on the OP switch could be part of your problem too, if it's not latched good or not tight on the pins.....

 

...and then there's always this.....

 

Same issue here with pressure. Changing the switch made it worse... found my gasket was shot on my oil pan and rms was leaking.
Almost done with the fix and I'll let you know how it goes.

 

Sorry for the late update. The issue must have been a fluke with my oil pressure sending unit. I reached down and slightly straightened the wires running out of the sender - no more problems. We have had many cold days since that happened and many miles and no issues.

To the prior poster, I had an RMS leak and the oil pressure was fine. I did fix the RMS leak (pain in the ***!) - I hope it goes well for you.

 

Unfortunately for you, the gasket on your oil pan and the rear main seal will do ZERO in repairing any potential low pressure issues you may be experiencing.

Hopefully you read this before you get it all put back together.

When you have the oil pan off make damned sure that your oil pick up tube screen isn't clogged since you are in there. I have seen many a sludged up engines have a clogged pick up screen killing oil pressure. *I am assuming the 4.0 has a screen on the pickup*

 

I realized that through research on the fix. Either way the pan and seal were leaking like a sob. Pick up screen was clean.. this is as soon as I got the pan out.

Just got it all back together.

 

And sorry for the unrelated reponse on this post. It was in a fatigued state from doing this fix.

 

She's still got really lousy pressure. It flirts with 30psi when I'm at 3000rpms & gauge drops to 0 at hot idle.
I can see moving oil at the top of the head, tried changing the switch (crappy new one that made it worse, replaced it with original one) but I'm still at square one. I guess I'll hook it up to a mechanical gauge tomorrow sometime and see if it's my dash gauge.
If I have to get in there again, I will to replace the pump.. on another thread on this forum I heard the pump doesnt really go bad?

 

It's certainly worth replacing the pump at this point.

Have you put a mechanical gauge on in place of your sending unit to rule out electrical issues? Definitely worth doing before tearing into it again.