i have 1999 5.3 L. silverado.at startup oil pressure at 40 psi.when temp.gets to normal pressure drops to around 20psi. lifters start to tap. i pull over and turn engine off. 5 min. later start engin
I had a couple of engines do this too me also, 1 had a bad oil pump, the other had not been serviced properly and crud was plugging up the oil passages to the top end, and the 3rd was the cam bearings excessive clearance. Yours sounds like an oil pump failure.
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