Oil Pressure jumping around

[Viva Las Vegas JDR]

I am what you might call a gauge watcher. I am always looking at the gauges to make sure all is well. I noticed the oil pressure dropped considerably. I drove a few miles and no change. Just when I was going to pull over the pressure when back up to normal. Why did the pressure drop ? the oil has been changed with less than 500 miles on new oil. I thought of the oil pump going out but that's just a guess.Any kind of help would be grateful.

[ccjohnson]

My oil pressure drops when RPM is real low. But it comes back up as soon as engine revs.

[The Newell]

I can think of several of things it might be - weak oil pump, bad/clogged oil filter, foaming or frothing of the oil (bubbles don't have much pressure), water (from radiator) in the oil, bad gauge, bad pressure sending unit, or an electrical problem that affects the gauge or sending unit (they depend on 12v power, good ground, etc). You kind of have to use a process of elimination. Changing the filter is an easy step and so is changing the oil, though it seems unlikely the oil is contaminated.

[77newell]

I had something similar happen recently on my 77 coach with 6V92. In my case the pressure would not pick up to "normal" levels after driving for awhile and then slowing to idle and accelerating. It was reading about 20 PSI low at speed and almost zero when at idle. And then sometimes it would just spontaneously pick up. Since I have a pressure gauge right next to the transmitter I checked it against the panel gauge and noted that the panel was reading low. I checked the ground of the transmitter it was OK and ultimately concluded it was the transmitter.

Can't say this is your situation. If the gauge's readings are jumping up and down it is most likely an electrical problem. I say that only because whenever I've had a mechanical failure the pressure went down and stayed down. An oil pump may wear and lower pressure very slowly but if the drive shaft breaks the pressure will suddenly drop and in my experience stay there literally at or very near zero as the tub ends at the breakage point rub each other into oblivion. Unless your engine was full of sludge the filter wouldn't have plugged 500 miles into a oil change, but if it did plug the pressure would drop until the bypass opened and then pressure would return to normal and behave as usual.

[Viva Las Vegas JDR]

Ended up replacing the oil pressure sending unit. Apparently, That fixed the issue.

JDR