RumT said: (quoted from post at 12:51:13 09/02/13) The spring could be weak and allowing oil to bypass all the time. You could have 30 psi at start up, due to cold oil viscosity, even with the plunger off the seat. Oil reaches operating temperature and pressure drops.
Possible but incredibly unlikely IMO. I'll hazard a guess that over 99.9999% of the times that an engine exhibits these symptoms it is because the engine is worn and internal oil clearances, including the pump itself, have opened up. In fact the only advantage of the oil pressure gauge versus a light is as an an indirect measure of internal clearances. When new TOOH's Cadillac Catera pegged the gauge at 80 PSI when cold and made 60 PSI at road speed on a blisterrng hot summer day. Now it still pegs the gage when cold but only makes about 45 PSI when hot. At 150K miles I'm quite sure that is a sign of bearing wear not a leaking oil pressure relief valve.
This post was edited by TheOldHokie at 10:19:40 09/02/13.
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