Having just replaced the engine (4jb1t) in my bighorn i have had a small problem with a leak from the oil filter housing ware the housing attaches to the engine block only when the engine is cold clearing up within 5 to 10 minutes, after noticing the leak i payed a bit attention to the oil pressure at cold start up noticed it was climbing to 6 Kg/cm2 if not a little higher dropping to normal levels as as soon as engine warmed up a bit
First i thought it could be the relief valve situated at the bottom of housing changed it for another no change
Decided to remove filter housing for further inspection having downloaded the engine manual from club isuzu (thanks ) I was able cross referance, To my surprise the safty valve situated beneath the oil cooler had been incorrectly assembled, The ball bearing had been placed beneath the spring instead of on top causing pressure problems in the housing and properly causing the relief valve not to function properly
This caused excessive oil pressure which was forcing oil past the housing oil ring when engine was cold, Replacing the valve correctly as compleatly rectified this problem oil preasure when cold now toping out at 3.8 Kg/cm2
Cant see this beeing a common problem but info might help others with a problem on a engine they dont know the full service history of
In hindsight i should have cheakd out the filter housing before i installd engine as removibng it was a little dificult due to lack of room
Thanks again to club isuzu for the engine manual as it saved my life in sorting this problem