2004 GMC not holding oil pressure
When I turn the car on it shows only about 10 on
the oil pressure and I hear knocking. Flushed out
all the old oil and did full oil and filter change. After
the oil change when I first started it up and acted
the same on 5 to 10 for a few sec then it jump up.
it looks fine. Turned it off later I went to start it
again and it did the 5 to 10 and stayed there.
sounded horrible knocking again and no oil
pressure? No leaks?? Any ideas?