Pajero Owners Club of South Africa

I have a 1989 Pajero with a 4D56 2.5L intercooled turbo diesel motor that has done 320,000k but was rebored & bearings etc at 285,000k. What should the oil pressure be at 2,500rpm when the oil is hot? My motor shows 1.5 to 1.8 bar and I have concern that this may be insufficient.

On startup when the oil is cold ( Not less than 15°C here in Richards Bay) the pressure is 4 bars. I have the motor out at present to replace the flywheel gear ring and have dismantled the oil pump to look at it. It consists of an outer shell with gear teeth on the inner surface and an inner shell with teeth on the outer surface. The inner shell is driven by the main crankshaft. There does not appear to be any noticeable wear on the moving surfaces.

Can anyone help?

Perhaps I should add that the 4D56 turbo engine is also fitted in Colt bakkies made up to 1996 as well as the latest Hyundai bakkies.

I don't have a manual that covers the exact engine in your vehicle, but I have one for a slightly newer 4D56 motor. I can't find a proper spec for the oil pressure, but the manual says the oil pressure switch will only activate at 0.49bar.

Seeing as you have the pump out, you can check wear using a feeler gauge as follows:
1) Measure gear tip clearance between the crescent and inner gear (design spec 0.22 to 0.35mm, limit of acceptable wear 0.5mm)
2) Measure gear tip clearance between the crescent and outer gear (design spec 0.12 to 0.22mm, limit of acceptable wear 0.4mm)
3) Measure side gear clearance between the inner/outer gears and housing using a straight edge (design spec 0.04 to 0.1mm, limit of acceptable wear 0.15mm)
4) Measure clearance between outside of outer gear and housing (design spec 0.12 to 0.18mm, limit of acceptable wear 0.3mm)
5) Measure clearance between the lower front cover and the little lip on the inner gear (design spec 0.03 to 0.09mm, limit of acceptable wear 0.15mm)

In addition to oil pump wear, low oil pressure could also be due to worn bearings (mains and big-ends) or if the wrong size bearings have been fitted at the rebuild. This leads to too much working clearance which in turn prevents sufficient oil pressure to be generated in the lubrication system.