What are the possible reasons for slow oil pressure on start up

Posted by Bill Butterworth On 2012/12/10 23:49:08

Oil pressure is good once car is running for a while. Do others with 356 engines experience this slow build in oil pressure, (one minute) ? Completely cleaned oil filter and blew out tubing to and from oil sending unit also to filter and return line to block. Changed oil and filter and the oil is amazingly staying almost clear, not dark brownish black like drained oil. Checked bottom pan through the drain hole with a long screwdriver and pan bottom seems clean and screwdriver did not have any sludge on it when removed. So system seems clean and pressure builds to 50 psi when rpm is around 1000-1500. When engine is hot and at idle (500 rpm) oil pressure is just below 40 psi. Could this mean the pump is weak and should be rebuilt? Would appreciate any information.
Thanks