I have a 2005 Sierra with a 5.3 LS with 210K. Engine oil was sludgy and it failed a coolant pressure test so I changed head gaskets. Oil looks good now but I have a tick sound coming from engine and oil pressure seems lower than normal. Around 35 psi. Should I replace oil pump?
I have almost the same exact truck with the 5.3 and my truck runs at 48 psi on a cold start but drops down to 38 psi once warm. Every engine is a little different as far as oil pressure is concerned because of the different tolerances in the engine assembly. If your truck behaves similarly and is 35 psi when warm I wouldn't worry about it. Lifter tick is a very common problem on the 5.3 engine. If you have dramatic changes in your oil pressure from time to time you could have a bad oil pickup o-ring. This causes the oil pickup to suck air into the oil pump under certain conditions resulting in brief oil starve situation.
35 does sound low. Could be the pump but I think the screens can get clogged too.
