Weird oil pressures

[Aaron IIA]

The normal oil pressure in my 2.25 is 50 psi with a steady needle. On hot days on the highway, it will climb to 80 psi with a fluttering needle. I use a mechanical guage. If I pull over and idle for 3~4 minutes the oil pressure returns to normal, but returns to a high and fluttering reading after a further 10 minutes or so of driving. Has anybody ever experienced this before, and what could be causing it?

Aaron.

[Johnno1969]

Hey Aaaron,

Sorry....can't think of anything too helpful there. Mine also sits on just over 50 psi on normal running (though if I speed up too much she starts to spit oil out through the breather); I've got a mechanical gauge too... all I can think of is that the heat may be causing the oil in the capillary tube to behave strangely (boil?) and give you your "fluttery" reading. On hot days, or with a hot engine, though, my gauge has never done that. How hot has the engine been while this has been happening to your gauge?

John

[Blknight.aus]

your oil pressure relief ball valve spring is letting go and you may need to change the oil filter. you may also find that your gauge has oil in its bordeau tube and is miss reading.

[Aaron IIA]

The oil filter has travelled about 4000km. The oil would average a bit less than this, as oil is added to replace that which has leaked out. I will change the oil and filter soon, as this is the easiest to do. If the relief spring was letting go, I would expect the oil pressure to drop. It is as if the spring is holding the ball closed, and then chattering the relief ball against it's seat. If changing the filter doesn't help, I may change the whole filter housing and relief mechanism. What temperature should I expect the sump to be when operating in hot conditions? If I could get a laser thermometer, I could measure the temperature of the sump and compare it to what would be expected. The oil line to the guage is nylon, and located on the right side of the engine. This is on the opposite side of the engine to the exhaust, so I would expect the temperatures around the line to be less than the boiling pressure of the oil.

Aaron.

[Blknight.aus]

ignoring the high pressure for a moment, IME if the mechanical gauges start to flutter thats usually the first warning sign of the spring starting to go.

first thing ID do is put a regulated 40psi air supply onto the tube to the gauge and see if the gauge is telling the truth.

[Aaron IIA]

Test the gauge. Good idea. I am also borrowing a test gauge to see what that shows.

Aaron.