i have a 98 silverado with a 350 vortec. when i crank it when its cold it is perfectly fine and oil pressure is about 60. after running for about 20 mins and the motor warms up it has a slight knock and the oil pressure drops to 0. when i give it gas the oil pressure goes up just a little but not much. what could be wrong? is it the oil pump? i was thinkin if it was the oil pump it would do it cold or hot. any help is greatly appreciated
sounds like bottom end (bearings ) when it’s cold the oil is thicker after it warms up ,oil gets thinner ---- shut it OFF , see if you can grab the harmonic balancer on the front (probably from underneath the truck is best )and move it foward and backwards any , if so the thrust bearing (mains ) are gone.