You've got a lot of dirt in your oil.
I have a 460 Ford engine in my motor home. There is an oil pressure sending unit that screws into the rear of the block. A wire is attached to the top of this unit that sends information to the gauge in the instrument panel. I have been getting about 6,000 miles on one of these before it plugs up. If I clean it out, it works fine again for another 6,000 miles. My question is, am I getting an accurate readings after I clean them out, or should I be buying new ones?
TOM: Sure you can clean 'em out, Ed. A clean one should be just as accurate as a new one. But my question is why are they plugging up?
RAY: And I think the answer is that you've got a lot of dirt in your oil. The first thing you should do is make sure your crank case ventilation system is working properly. My guess is it's not, and that sludge and varnish are building up and plugging up your sending unit.
TOM: Once the ventilation system is fixed, try changing the oil twice in about 500 miles just to clear out whatever remaining crud may be in there. After that, you should be fine.
RAY: Then you can stop worrying about your oil pressure sending unit, and start concentrating on more important things, like how you're going to explain to your neighbor why you keep backing over his tulips every time you try to get this behemoth into your driveway.