Rebuilt engine with 20k miles developed leak at rear of engine on passenger side. Engine has mds delete with plugs in place of solenoids. Running 5w-20 Mobil One synthetic. Oil pressure at start up when cold is 65psi then drops to 45psi when engine is warm at idle. Put truck on lift and cleaned from oil filter back to transmission crossmember. Had small oil leak at oil filter gasket and oil temperature sensor which was fixed by tightening oil filter to 1 1/8 turns after contact and oil temperature sensor one more full turn. Initially thought rear main seal was leaking but oil looks to be weeping from back passenger side of engine behind transmission bell housing. Any reply’s or suggestions are welcome. Thanks.

 

Is there a soft plug back there in one of the oil galleries? Gonna be a bear to inspect/fix.... engine or trans will have to come out.

Unless.... is it running down from up on top somewhere??

 

There’s a plug in the oil gallery between the cam and crankshaft. I’m going to look for the leak again tomorrow but the transmission is probably going to come out. It’s 2 wheel drive so there’s that. Just wanted to see if there was a source for a oil leak that I can’t see. I got the rear seal for the engine, front and rear seal and filters for the transmission. One thing the rebuilder used gasket maker on the oil pan gasket and it’s weeping a little oil. Didn’t know if using Permatex was a good idea in that application.

 

A real gasket for the pan would likely be a better idea.

 

Determined oil leak was at rear main seal. Removed transmission and found crankshaft flange had 3 knicks from machining when engine was rebuilt. Contacted rebuilder and he advised dressing knicks with file and installing crankshaft flange collar. Installed collar and new seal and problem solved.