low to no oil pressure after rebuild
rebuilt. bearings /rods/ new oil pump/sensor/lifters/ every thing . starting oil pressure 60psi. after 30 min. warm up low to no pressure. been back thru 3 times . same thing .. im missing something ..
2001 3.8 chevy/ buick k vin sorry
Did you have the block bored?
Bearing clearance might be out of spec, possible clog, oil not heavy enough, or there could be an internal oil leak early in the oil system that's temperature sensitive.
i installed cam bearing as you would a norm motor im thinking from reading others. hole is to big. some redrill smaller..oil is 5 w 30 bearings plastigauge good. oil relieve valve is good not sticking. new pump and gasket.
didnt bore block all was good no ridge. old bearings looked good for 100k
I take it had good oil pressure before the overhaul, so the problem is like Brian stated that there must be a oil pressure leak early in the oil system possibly one of the new parts goes into failure when it gets warmed up, oil pump could be sucking air on the intake tube or pump seal, that won't show until it reaches operational temp. The reason why I asked if the block had been bored is I had a engine bored out and they bored one cylinder off center ever so slightly and caused a hairline crack in the block, it ran good until it warmed up then the oil pressure went bye bye. Scratch one engine block.
As you probably know, oil pressure is a result of a resistance to oil pump output. The resistance comes from the main journals and the connecting rod bearings. Something has to be going on with them. Nothing else is changing enough when the engine warms up.
If you are doing another tear down, change the oil pump, and make sure it is one for your engine model. Make sure the bearings are not in backwards or upside down. Sound silly, but it has happened. I lost a 51 MGTD motor because of an incorrect spring rate in the outside oil pump. This is not your problem, but something simple that is overlooked or a wrong part is replaced can cause the issues. As others said, check cylinder pressure, check the bearing size, correctness and placement. To fix it, you may need a complete tear down and I'd rebuild with new bearing all around and oil pump. Air in the system or bearing failure that does not maintain pressure. Also check the sending unit, the line to the pressure gauge, and the gauge itself. I'd get an external reading on the pressure using test equipment before the tear down though and make sure it is not your send/sensing units. Good luck and have fun.
think its to much bearing clearance..the oil relief valve just lets oil flow thru filter and you can block it if you want all the oil to run thru the filter first but that wouldt explain it.. the engine gets hot and clearances expand ..pressure drops....im sure you set up the pickup... good luck
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