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I just replaced the 4.7L engine in my 2002 Ram 1500 with a remanufactured long block, actually, this is the second one!

The original engine blew a head gasket and hydraliced a cylinder, bending several valves, my daughter learned not to start an engine after large amounts of white smoke have come out of the tail pipe!

Because of the mileage, I opted for a remanufactured long block. After installation, the new engine had a problem: excellent oil pressure at all rpm until the oil reaches operating temperature, then the engine shows 0 psi at idle, and 48 psi at about 1500 rpm.I verified the pressure with a mechanical gage. My immediate thought was bearing clearance or oil pump problems, so I contacted the rebuilder and they sent me a replacement engine. Now I've R&R'd the engine twice and the replacement has the same oil pressure problem! The only components that moved from one engine to the next, that would have any effect on oil pressure, are the oil pan, the pump pick up, the pcv and the valve cover ventallation system. I did install the o-ring that came in the gasket set for the oil pump pick up and I'm wondering if there are different sizes. I'm thinking that the engine has some kind of internal leak ,and it seems unlikely that a rebuilder would send two in a row with the same problem.

Does anyone know about the possiblity of different size oil pump o rings or have anyother suggestions? the engine runs great, and if it wern't for the annoying "check gages" light and chime at idle, I wouldn't know there was a problem - aside from the gage reading!
 

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I don't know about different size oil pickup o-rings, but a smear of RTV around the o-ring sealing surface should seal the joint. Are you using a 5W-30 motor oil?
Zero psi is bad. Minimum oil pressure at a hot idle should be at least 7 psi and I would feel better if it was around 20.
Could the front cover oil pump pressure relief valve be not seating or stuck slightly open?
 

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Thanks for the response, I can use all of the help that I can get. The manual that I have shows the relief valve on the 4.7 engine to be located in the pump, not in the timing cover. I don't know if I'm missing something. As for the RTV, that has crossed my mind too, but I'm hoping that someone will have encountered this problem before and have a solutiuon.
 
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