I have a 2003 Cargo Van with a 318 and has 120,000 miles on it. I was losing oil pressure when I would accelerate rapidly at high RPMs. The pressure gage would instantly drop to 0 and the valves would soon start tapping. But if I pulled over and shut the engine off the pressure would come back up to normal, aprox 60 psi. and be ok until I would have accelerate rapidly again. But now I lost oil pressure and it won't come back up. I had the oil pump changed with a high vilosity pump and anew filter and oil, and still have no oil pressure, and the valves are tapping so I know its not just the sending unit. The lower end sounds good, no noise.The mechanic that changed the pump said he thought it may have bad cam bearings, but would this cause instant oil pressurelossat highrpm and now no pressure? The pressure was allways either good or 0 never low.Is there a pressure relief valve outside ofthe oil pump?I must be overlooking somethingfor the pressure to come up to normalafter shutting the engine off and restarting. I would very much appreciate any advice before I have to replace the engine, Thanks, Dan

 

Dan,

I'm gonna do a little guessing here. The simple thing might be that there is a break of some sort on the pickup screen to the oil pump. As in its sucking air. This sounds very similar to the old race cars before we could get better oil pans with windage trays in them. I hate to say it but, i'd be pulling the pan and removing the pickup to the oil pump and checking it for cracks or any other openings that might cause the pump to get air instead of oil.

I would also try bringing the oil up to running temp then increase the rpm to 3500-4000 and hold it there to see if it maintains pressure. Its possible that the oil return passages in the heads are full of crud and your holding all the oil up on top until it has a chance to drain. A very potent oil sides engine flush might resolve this, but, if the engine is that crudded up, and you break it loose all at once, you'll have a plugged oil screen----then you'll definitely have to pull the pan. Might be a good idea to pull the valve covers too and check.

 

Thanks Gone Fishin, Im going to pull the pan and valve covers and clean the oil gallerys and also check for leaks on the pick up. thanks Again, Dan