Just put a new head gasket in the 4.0 last week. The jeep has been driven about 150 miles since. No oil or water leaks to date. Today for the first time while sitting at a stop light I noticed the oil pressure at 0. I stopped and checked the oil. Found it was about 1 quart low. But still no water in the oil.

Although while sitting still at lights the pressure would drop to 0 at times it would hover around 10. While driving it would normally hover at 40. Now it is just making 25 30.

While sitting still and the pressure at 0 there are no strange sounds like tapping or anything else. When I shut the engine off after sitting for a few minutes with no oil pressure on the gauge i still heard the same amount of oil trickling down through the engine.

What should I look / listen for? what should I do next?

Thanks in advance for your help.

Clean the connection to the pressure sender... If that don't work install a new sensor. If you truly have no pressure the valves will make so much noise you would be asking about the noise also.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

Just to confirm, the oil pressure sensor is directly in front of the oil filter correct

Yes, clean the connections and/or replace the oil pressure sending unit. They're not expensive. My 2.5L is about 28lbs at idle warm and around 60lbs cruising.

Good point, What should my pressures be. I will pick up a new sensor tomorrow.

40 at speed is plenty.. Most will show 50 or better. At idle if the lifters don't colapse you are ok.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />