Hi all, the oil pressure light illuminated at tick-over, so I figured I'd better start exploring, the obvious candidates being a loose oil pump bold or the relief valve.

I dropped the sump pan and checked the oil pump bolt which was fine. I installed a new one which included locking compound to help me sleep at night.

I removed the plug from the oil pressure relief valve. The spring checks out fine measuring 42 mm as it should. However, the plunger needed to be pulled out with pliers suggesting it's a strong candidate for the oil pressure warning light. The plunger looks fine.

I thought it would be wise to check the bore of the valve where the plunger sits. The plunger sleeve itself looks okay but it's not looking good above and below it - see photographs. It looks as though there's metal sheared/fractured. Does anyone know what this should look like?

Thanks in advance.

Hi, IMO you should have replaced the pressure switch first to rule it out cos that'sthe first suspect before going so far with the diagnose... i dont know how that valve should look like but you can also measure the pressure with a gauge in the switch's port

sierrafery said:

Hi, you should have replaced the pressure switch first to rule it out cos IMO that'sthe first suspect before going so far with the diagnose... i dont know how that valve should look like but you can also measure the pressure with a gauge in the switch's port

Click to expand...

Hi Sierrafery, thanks, yes, the pressure switch has been replaced. Got the same result. I have also connected a pressure meter and the pressure is low at anything under 1500 revs. It rises to 3 bar with revs at 3,000 suggesting the pressure relief valve was stuck. Indeed, it was stuck when I stripped it. Had to remove it with pliers.

Have now removed the oil stiffener plate/oil pump assembly and disassembled it. The concern expressed in this image is just part of the design and how it was manufactured. This gap allows oil released by the relief valve to return to the input side of the oil pump.

I have now ordered a replacement oil pump/oil stiffener plate as it has been suggested elsewhere that the seat for the relief valve plunger should be more fully rounded. This D2 is mainly used for towing so I'd not want it to fail.

Thanks again for posting.

Hi all, here's a photo of the oil pressure relief valve seat from the new oil stiffener plate/oil pump. As you can see, it covers a full 360 degrees. Fitted and working. Oil pressure test shows a steady 3 bar at tick-over, rising just a little with revs as the valve opens.