High oil pressure

I'm pretty clear on things that can cause low oil pressure, and suspect that my issue is likely sensor-related, but: what can cause high oil pressure? Just curious as I searched this but didn't find any solid reasons given for what might actually cause it.

What brings this up is that I've noticed my oil pressure gauge occasionally pegging at 80. Sometimes it happens right at startup, other times it happens while driving. Doesn't seem to matter if the engine's warm or cold. There're no leaks from the filter, valve cover gasket, or anywhere around the head, the level's good (right at the MAX) mark, and there's no noticeable oil consumption. I did have the oil and filter changed about 600 miles ago, but this had happened a couple of times before that. FWIW, this is on a 2000 Limited with the 4.0.

Oil pressure is typically 40psi at cold idle, 25psi at warm idle, and 45-50psi running. Like I say, I really suspect the sensor is on its way out but would like to know any likely causes just in case.

I would have to concur with your thinking the sensor is failing, or there is an intermittent break in the wire.

Corrosion on the connector can do it too. If you disconnect the sensor, the oil pressure pegs the top end (after '90)

casm said:

Oil pressure is typically 40psi at cold idle, 25psi at warm idle, and 45-50psi running. Like I say, I really suspect the sensor is on its way out but would like to know any likely causes just in case.

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Sounds like the gauge sending unit is indeed on the way out. If your gauge still pegs occasionally at 80psi with a new sending unit, the likely reasons are as follows:

Oil pump pressure relief valve sticking (most common)
Intermittent open circuit due to faulty wiring or connector
New sending unit is a dud

i had that happen on mine and even after putting in a new sending unit it didn't go away. by accident i discovered that one of the connectors inside the plug had spread apart and was making intermittent contact with the pin in the sending unit. i took a very small pick and bend the little tabs of the connecter together till the opening was almost smaller than the pin in the sending unit and then plugged it back in. the pin then spread the opening in the connector just enough to slide in and it had a nice tight fit. no problems since.

My sender is fine - I got the same results when I added Slick 50. Startup is 80 - 90#, warmed up 45. I run 10-40wt. Before the teflon, I was getting 50# startup, 25# warmup. I added it just before my pan gasket starting leaking and I know I put 60 quarts of oil through it until I finally got it to stop. Apparently Slick 50 doesn't get washed out with oil changes so much

I added Lucas recently and now I have noisy tappets the first few minutes, so no more Lucas.

All that to ask: when did the hi pressure start, what oil, additives, etc. It may be something else.