Oil pressure question

Mount your gage directly to the oil manifold and see if that makes any difference. May be a clogged or crimped oil line.

Not getting much flow from the oil cooler vent line when running would indicate there is an engine oil pressure problem or something isn't right with the oil cooler bypass valve operation in the oil filter base. Do you have all the correct parts for the full flow oil filter installation?

Hi Old Magnet,

Thanks for your response to my post about my low/no oil pressure. I think that I have the answer---at least all the cues fall into place.

The oil pressure gauge on my D4 is piped right off the rear end of the oil manifold and the tube is clear. A substitute gauge indicated the same readings. Also I am confident that the full flow filter is assembled correctly.

My oil pressure problem got worse and worse over time. Clue one: The weather in west central Wisconsin got colder and colder. The oil thickened.

The oil pressure comes up normally while cranking the engine but goes down when the engine starts. Early on, when the weather was warmer the pressure would eventually come back up. When the engine was warm the pressure was good.

In a Cat manual I found information about the pressure regulator in the oil pump. A piston with a tapered end is arranged to be able to constrict the oil flow through a passage to the input to the pump. A spring normally forces the piston out of the oil flow. The other end of the piston is fed oil from a bypass at one of the main bearings. This oil pressure drives the piston against the spring. The higher the pressure, the more the piston constricts the input to the pump.

This fits with my observation that the oil pressure comes up while cranking (low pressure) but falls off when the engine starts (higher pressure) from the main bearing bypass.

My guess is that the piston is hanging up somehow or the spring is weak or broken and fails to clear the piston from the input path.

It sounds like a major effort to service the pressure regulator is in order.