ok i have searched everywhere for a solution to this, and really cant find anything other then things i have already done so will give the story and listen to ideas.

my boss bought a 2004 2500hd in good shape for 1k, problem was oil pressure was low, and engine was tapping slightly, was told by the guy i got it from that the chevy dealer diagnosed it as a bad oil pump,

so i took it home, and first thing i did was hook a mechanical gauge in place of sending unit to make sure there was not an issue there as i had read they tend to go bad, and got same readings

so i replaced oil pump, put it all back together, and still same thing about 8lbs at idle, and will go up to almost 20 if you drive down the road, not enough

so a few weeks ago we had a mechanic buddy replace the the crank bearing and all in the bottom of the motor, he suggested that was probably the issue. he put it all back together, and had no oil pressure at all. so thinking they may have not gotten the pick up tube back in or the o ring damaged they dropped the oil pan again, and checked it they said it was in like it was supposed to be, but apperantly while they were under there they pulled it down and shot some engine builder lube into oil pump, put it all back together, and started it up, now it had oil pressure but still the same about 8lbs at idle, and close to 20 if you drive down the road

i am baffled as to where the oil pressure is going, it does have a tap (lifter i am assuming) the mechanic said while he was in there they looked up at the cam bearings, and said they all looked good (i did not know you could see them from the bottom, and even so how could you tell if one was spun without pulling the cam?)

before we through more money at it we are now trying to narrow it down a bit more

the truck still seems to have all of its power it runs good no missing stumbling or anything, no smoke, oil is good clean, filter is new. the truck honestly runs well except for oil pressure, and a tap (which is probably mainly due to low oil pressure.) have had a few suggestions of a calapsed lifter, however everything i have read says that a calapsed lifter will make it run rough?

am open to any and all suggestions, we dont want to throw a ton of money at this motor trying to fix little things that just not doing it, if the cost gets to high it going to get a junk yard motor

any and all suggestions would help

 

You can't tell if the cam bearings are good or not from the bottom. You can see them but can't tell if they are worn out. If the main bearings were worn then it is a good possibility that the cam bearings are also worn.

 

That is what I figured....so it a good possibility that worn or spun can bearing could be the cause for pressure loss?

 

If you don't want to go back into the engine, just shim the pressure spring in the oil pump with a couple of very small washers or 1 small nut