Astro Van oil pressure problem

[Ms Grumpy]

I need your help with this one. Last night it was about 45 degrees, I was out and when I went to start my van after it had sat for about 3 hours I heard a noise that sounded a little like what a fan blade sounds like when it hits the shroud, or as David said it sounded like an exhaust leak to him. Anyway after about a minute the sound went away. I watched the gauges all the way home and nothing really seemed off. Now about a week ago I did notice that the oil pressure seemed to drop to about 25-30 when stopped, prior to last week it would usually drop just below 40 when stopped or at an idle and the highest it usually went was about 50-55. I checked the oil and it was within acceptable range.

Forward to this afternoon. Temp was near 60 and I started the van and the same noise from last night, this time it lasted for about a minute and a half. But when I went to pull out of the driveway I stepped on the gas and the oil pressure went up to 80, the highest on the gauge in the van. I was in the street and decided to turn around and park the van back in the driveway. The oil pressure stayed high until it shifted, then it would drop to about 50 and then rise again to 80 as I accelerated. I got back to the driveway and decided that I would see what would happen if I let the van get warm. As soon as it was warm I stepped on the gas and the oil pressure was back to normal. I pulled the van out and took it for a 15 mile city drive and it was normal. I parked the van and let it sit for about 1/2 hour and when I started it, the same BS with the oil pressure until I let it warm up.

I have talked to a few people and they suggested that I have the sending unit for the oil gauge checked. I am wondering if anyone has any suggestions for other things I should check or know of any issues like this with the Astro. This is a 2000 AWD Astro with 185,000 miles on it. We have taken pretty good care of this van for the past 10 yrs that we have owned it.