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Jerry, Master Mechanic
Category: Dodge
Satisfied Customers: 1704
Experience:  ASE Master tech, 30 years exp. troubleshooter, driveability tech
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I have a 2003 dodge ram, 4.7L with about 115k miles that has

Customer Question

i have a 2003 dodge ram, 4.7L with about 115k miles that has low oil pressure after the vehicle warms up and is at idle. This started about 2 weeks after i had someone replace the head gasket on it because water was getting into one cylinder. The mechanic was doing the work in his spare time and it took him about 9 monthas to do. So the engine was torn apart for most of that time. The oil pressure starts out at about 40psi and after the vehicle warms up it drops down to just a couple pounds before i shut it off. I have tested this with a mechanical gauge so it is not a faulty sensor or gauge in the truck. Things i have already done. I removed the oil pan and the filter on the pipe going to the oil pump was not clogged at all. It was very clean. I replaced the piston rod bearings which were worn but not horrible. This did not make the situation better or worse. I have done some research and think it is likely to be either rod bearings or the oil pump. Is there any other things that i should check and is there a way to determine whether it is bearings or oil pump as that will likely give me direction on what way to head with the repair.
Submitted: 2 months ago.
Category: Dodge
Expert:  bill replied 2 months ago.

on the 4.7 and its sister the 3.7 the oil pressure is created via the MAIN bearings if coolant was getting into a cylinder chances are it got into the oil, oil into the coolant will wipe out the bearings pretty quick, since you said there was wear on the rod bearings (the LAST THING to get oil) the mains are very likely worn too.

this engine uses a split block design that actually splits the lower half of the block and casts the main caps into it so you almost NEVER get a main bearing knock with this design.

the only correct fix is pull the engine and replace the main bearings and even then this MAY NOT bring the oil pressure up to the 15 to 20 psi it normally has at idle, the clearances on bearing to crank are VERY tight in the order of .0015" to .0025" which is far tighter than any older engine

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