Cadillac Repair: Oil pressure, oil pressure gauge, pressure relief valve

Question
When I change the oil and filter in my 92 Deville 4.9 its taking longer to restore operating oil pressure after start-up. The oil light just stays on...and on...(for about 2-3 minutes...which seems like forever). Its not the switch because I can hear the lifters rattling just before the light goes out. I even switched to factory Delco oil filters. I'm thinking of adding STP to the oil to protect the bearings. Any ideas?   Thanks

Answer
Hi John,

      An oil pressure gauge would be a good thing to use here. You would need to remove the sending unit that is near the filter and screw in the gauge and see what the pressure is. Cadillac has an unusually low minumum pressure that is around 6psi at a hot idle in park. Because of the year you could have a problem with the pressure relief valve in the oil filter adapter, the oil pump o-ring could have cracked and lowered pump pressure, because of the pump age it is worn out and needs to be replaced or bearings are worn and then pressure can't be held.

      Some parts stores like Auto Zone or OReilly have loaner tools and the pressure gauge might be one of them. If it is low try replaceing the oil pump and o-ring and see what happens. Thats what I would do. Let me know if I can be anymore help. Bill