Oil Pressure problem with 1991 5.0
 

I've searched through the subject and found much to read. But none quite like my situation. Was running about 55 or so when I noticed the oil gauge needle dropped to L. Went only a little ways to a station and checked the oil level. About half a quart low. So, started back up, pressure looked fine and moved on down the road. Mile or two later needle wobbles and goes to L again. I listened for engine noise and seemed to hear an increase in rattling/tapping. Pulled over again and stopped. Restarted the engine, pressure fine but when I revved up the engine the pressure would drop but return to normal at idle. Once again I took off and went short distance to find some oil. Topped off to full and made it home.
Based on my reading in this forum I bought a new sending unit and will put that in.
But I am thinking sludge here. Truck only has 63K miles on it and all of that is probably short trips (farm truck). Belonged to my father-in-law and I would not doubt he only used straight 30wt oil and only when he felt like it. Other than the sending unit replacement idea, what can I do to address my suspicion of sludge stopping up the engine drain holes and letting the pump starve? Any way to easily verify and de-sludge? Thanks.

coulld be a sludge problem blocking
oil pickup screen in pan at idle the stuff
falls off screen allow oil in at low volume
at higher rpm more volume needed sucks crap over screen
have seen this a couple times
mitch

Thanks for the reply. Is there a way to de-sludge without dropping the pan? (Other than what might come out during an oil change.)

You cab buy engine flush at auto part stores, I don't like it myself. The flush is basically kerosene. On my old bronco I used to flush it by adding a quart of ATF about 20-50 miles before changing the oil and filter. Just changing the oil and filter will help. After changing you should check the pressure with a gauge to make sure you have the correct pressure.

remove the pan i know it's apita
but i don't think any flush will
clean it properly
mitch