After the head gasket was replaced I noticed a problem with the oil pressure gage. When the jeep was started cold the oil pressure was about 40psi sometimes 50. However when the engine was warm it would drop down to 10 PSI. After a few days I noticed while sitting at a stop light that it was dropping to 0 with the check gauges light on.

Now the valves did not go flat and the engine sounded normal. I finally changed the sending unit on Friday. This didn't help any the gauge still drops after the engine is at running temp.

I changed the oil and filter again just in case the filter got plugged up with junk left from the head gasket change.

Again there was no change. Since I felt this must be a fluke I continued to drive the jeep. As a Chief Officer of an Ambulance service I was requested on a call today and needed to respond. When I returned to the vehicle after it had been sitting about 20-30 minutes I could hear the exhaust had a slightly different sound.

I am preparing to replace the oil pump in the morning, but I wanted to make sure that there was nothing else this could be. It just seemed funny that prior to the head gasket change there was no problem but just after this started to happen.

Is there anything I could have done wrong during the head gasket replacement or is it the pump??