High oil pressure

[bespander]

Dr. Lee,

The oil pressure on my Banks turbo'd 6.2 has been creeping up the last few thousand miles. At idle the gauge reads 40 psig, which is normal. At highway speeds, I frequently peg the gauge past 80 psig. The 6.2 currently has over 240k miles and I expect the oil pressure to decrease not increase, unless there is a passage plugging issue. The oil, DELO 15-40, is changed at 3k mile intervals. Oil temperature runs from 220-250F on an uncalibrated gauge, which is the normal range.

This weekend I replaced the oil pressure sending unit with a unit off an '82 6.2 and it didn't change the readings. I then changed the oil and filter, which did not change the high pressure readings. I did take an oil sample and sent it off this morning.

I am not sure what to try next. I have Aeroquip hoses that connect the engine to the stock oil cooler then a 35k BTU cooler in series and then return to the engine. I installed the second cooler in

[BobND]

Not to get ahead of Dr. Lee, I believe you will find that the sender port is connected internally to the main oil gallery for the lifters, cam, and main bearings.

That would mean it is sensing oil pressure of oil that has passed through the cooler(s) or the cooler bypass. So this would indicate plugged lines or coolers wouldn't INCREASE pressure AFTER the coolers.

Either you have a weird electrical issue (engine-to-chassis, or body to instruments) affecting the electric oil gauge, or the oil pressure relief valve on your oil pump is jammed closed.

I'd verify the pressure with a mechanical gauge, and if the pressure is REALLY too high, I'd say it's time to change out the oil pump.

[john8662]

Actually it could be the external coolers and associated lines. If you have restriction in the external cooler circuit then the bypass is used in the the block right above the oil filter, and you'll see higher pressures, but low volume.

This lesson was learned by another member who had set and engine on a dyno and plugged off the cooler line ports, had high oil pressure, until a rod bearing failed.

But in this situation, as with all other oil pressure complaints, you need to "T" off your pressure location and install a mechanical oil pressure gauge thats common at most auto parts stores. This is to narrow out the possible electrical problems, My 82 pickup pegs the gauge, but the gauge is wacky, the mechanical gauge I've got installed temporarily has proved what the pressure really is.

[BobND]

If you're measuring the oil pressure at the conventional port at the top rear of the block, how can a restriction AHEAD of the main oil galleries POSSIBLY cause high oil pressure at that point?

Obviously, if you're measuring the oil pressure at the oil pump output, the pressure would go up with a cooler system restriction, but how could the pressure go up, measured AFTER the cooler, and the cooler bypass valve, at the standard pressure sender location?

[CleviteKid]

BobND is correct, if the pressure is being measured at the port at the back top of the block.

The pressure gauges on the earlier trucks are known to be screwy, and I have a mechanical gauge on a tee with the electrical gauge, permanently mounted in the engine compartment. The gauge and circuitry in the dash can be screwy and changing the sensor itself will not do anything - I been there and I done that.

Dr. Lee :cool:

[john8662]

Upon looking further at the oil circuit in the book for the engines, I'll admit I was wrong, it would be lower that that spot.

Thanks for the correction BobND and CK

:rolleyes: