jsmith823

So I just noticed something weird with my jeep today. When it is hot (210) and I am sitting at idle, my oil pressure light will drop to 0. As soon as I start accelerating it jumps back to 20, which is where it sits most of the time. I hear no strange noises from the engine, and I have plenty of oil. I am pretty sure this is the sending unit, but does anyone have any advise?

jsmith823

This also doesn't happen every time I stop. Just occasionally. It was dropping at stoplights earlier, but it sat and idled in my driveway while I looked under the hood and was still up when I got back in the jeep.

tjwalker

Very possibly the sending unit.

Two options.

1. You could verify your pressure by installing a "mechanical" oil pressure gauge where the sending unit currently resides. Then you'll know for sure. These gauges can be rented from many parts stores.

2. Or you could take a chance and install a new sending unit. If you do this, do yourself a favor and purchase it directly from Jeep for the best reliability/accuracy/mating with your factory gauge. Aftermarket sending units are "hit and miss" with a lot of miss.

Oil pressure spec for the 4.0 is as follows:

*Not less than 13 psi at HOT idle

*Between 37-75 psi OVER 1600 rpms

jsmith823

So if it's not the sender, what should I try next?

tjwalker

Don't get ahead of yourself.

The fact that you hear NO strange noises from your engine when your oil pressure gauge reads zero would not be the case if you truly had zero oil pressure; you'd have some rattling.

Get a new sending unit in there and see if that resolves it. I think it will.

Jeepin4x4

It could very well be the sending unit. Im not sure if you know where it is or not. But anyway it could be the gauge, its not correctly reading or the unit. Im thinking its the sending unit though. You have low oil pressure in general it sounds like.

jsmith823

Thanks for the advise! I will pick up a unit in the next day or so and pop it in. It's right by the oil filter right?

I am kind of freaking out about this even though I know it's probably nothing. I am OCD, so little things like this really bother me. I can't afford an new engine

tjwalker

Gotta take this one step at a time. At this time, your symptoms point to the sending unit. The gauge itself can fail, but rarely does.

Go to your local Jeep dealer and buy and install that sending unit. It is located directly above the oil filter. Very easy to swap out.

Let us know the results!

fishtaconc

X2^ Most 4.0s rattle with good oil pressure.

jsmith823

K, I wasn't worried as much about the gauge as I was about something like the crank bearings being bad or something.