Well, I've got a question this time...
Just had the 4G63T rebuilt with new pistons after an unexpected ring failure after less than 15000 km. Prior to this rebuild oil pressure as indicated on the std 1G gauge was just above the low mark once the engine was hot. There was no reason to change the pump. There was no need to replace the bearings as these were done on the original rebuild. Bearings went back on the same journals.
Now, when the engine is cold, the pressure hits slightly more than midpoint between the low and high marks. Once the engine is warm however, the pressure drops to less than the midpoint between 0 and the low mark. There's also a quiet rattling sound under 2500 rpm that reminiscent of a slightly loose tappet. The noise was not there before this rebuild.
The guys who did the rebuild know Mitsu inside out and wouldn't get the oil pump alignment wrong, at least they have never done so before on my other Mitsu vehicles. The engine seems as smooth as it was after the first rebuild.
I know what a misaligned pump sounds like in the 4G64 SOHC, but I've never heard one in the 4G63 DOHC. Does the engine run with noticeably more vibration?
Could pump misalignment be the cause of the low oil pressure?
Its almost like there's something that's now looser in the cam area that's rattling and venting oil pressure more than it should be. Any suggestions?
Stewart DIBBS