I got the 2007 commodore/Lumina SS. I installed melling 10295 oil pump with a new sending unit. When engine is cold I get 300/320 KPA oil pressure, once engine is fully warmed up I drops all the way to 120/140 KPA.I use 10w40 engine oil because of the weather around here. Gets to 45 degrees C. What could be causing my pressure drop. Cam bearings? .. engine done only 63000 KM.

Edit: got the L98/LS2 engine in it and the car is factory stock

 

Anyone?
input would be helpful guys... forgot not tell you that the mechanic did not change the timing cover gasket nor the oil sump gasket. I am having doubts that he actually changed the pump.

 

If nothing else was touched and your oil pressure before was good I can't imagine it being your bearings. My guess would be the pickup tube o-ring being pinched. Have you changed your oil to be sure there isn't bearing material in there.

 

I am 100% positive that the engine has never been touched. When I bought it, it had fresh oil in it. I got rid of bit because the mechanic was supposed to change the oil pump. I used 10w30 but the pressure at idle dropped to 10PSI. I changed oil again to a thicker one 10w40. In all oil changes I saw no trace of bearing material or any kind of metal powder deposits.

 

Does it have VVT or AFM? What pump did it have in it before?

Oil pressure is going to drop as it gets warmer and the oil thins out, but it shouldn't be 10psi in a stock engine.

 

No AFM no VVT .. with 10w40 it sits at 15 PSI which is still worrying to me.

 

Is it possible to change the pump without removing the timing cover.!!!!!

 

Nope.