horrible oil pressure

[tonyjklh]

i have just rebuild my 4.0 about a month ago. had the block and heads professionally done, bored .20 over on cylinders. std size for all bearings. everything except the crank and rods were replaced. inspected the crank and it was perfectly in spec as well as absolutely no sign of wear.
now the problem is the pump is not working very well(at least im guessing its the pump). when its cold it does fine and hits 60-62 psi. after a few miles it starts idling at 20 than jumps to 50 at 2000 rpm. but as soon as at gets fully warmed up it will idle between 8-10 psi and will only get to 35 psi at 2500 rpm. as well my new rockers/lifters/pushrods are making noise now as well
does anyone have any advise that might help me avoid pulling the engine to change the pump?

 

[holyford86]

did you change the pump? what were your main and rod bearing clearances when you rebuilt?

 

[jhammel85]

I would return to whoever rebuilt it for you. It sounds like they may have some clearances out of whack. Don't drive it too much until it's right or they wont help you.

 

[tonyjklh]

i rebuilt the engine myself. i just had the block(bore, deck, cam bearings), heads done by an auto machine shop. all the assembly was done myself. i brought the crank in to the shop to have it inspected and they said it was perfectaly fine to use std size bearings. and looking at the crank i say no visible wear on it.
so im not sure how the clearances could be off. it sounds and runs great, no knocking or anything like that. except for the valve train noise that has developed now.

 

[tonyjklh]

also forgot to mention the engine had only 150,000 when i rebuilt it.

 

[tonyjklh]

I also forgot to mention that the oil pressure was working great for a week after I put it in. But after that it slowly started getting worse.

 

[alwaysFlOoReD]

Did you change the oil after break-in?

Richard

 

[tonyjklh]

I've changed the oil twice now. The first time was after break in. Second was because i thought i had a bad batch of oil.

 

[tonyjklh]

alright i just thought of something else that may be a problem. is it possible that the machine shop could have put the cam bearings in the wrong order? do they have slightly different inside diameters?
please anyone with any suggestions please join in. im pulling the engine next week to change the oil pump and want to make sure i get this fixed.
also is it possible for the crank to stay quiet but be bad enough to loose that much pressure?

 

[squealingtires]

alright i just thought of something else that may be a problem. is it possible that the machine shop could have put the cam bearings in the wrong order? do they have slightly different inside diameters?
please anyone with any suggestions please join in. im pulling the engine next week to change the oil pump and want to make sure i get this fixed.
also is it possible for the crank to stay quiet but be bad enough to loose that much pressure?

The cam only fits in one direction. Check to make sure you didn't lose any oil galley plugs up top and that the timing chain tensioner and guide are not cracked (They serve like a plug for the galleys but do have a small orifice for their own function of keeping the chain lubed and tight.) There is also a small hex plug below the tensioner.

Buy the Melling M328 pump. It flows 20% more and doesn't cost much more than the M128 OEM replacement. You should have a gasket on both the oil-pickup tube and where the pump bolts to the block. Hopefully the machine shop did an excellent job of cleaning up after themselves but be on the lookout for junk in the pan.

 

[flatblack]

It is an awful conclusion but you gonna have to put that sucker out and flip it upside down and pull the pan<< AGAIN >>. Yuck I do not envy you.
I would guess the oil pump is gunnysack or the gasket is leaking. None the less good luck.