Last week we encountered a 2003 Discovery with a failure I have not seen before. The car came to us with an oil light on most of the time, and lifter noise when the light was on. The noise vanished as soon as the light went out, confirming that the car has a problem with oil pressure, and not a problem with the oil light sender.
This engine is reasonably clean, and free of sludge. This wasn't a neglect issue.
We removed the front cover, and found the oil pump fractured. I have seen several similar failures in the past year, but most of the time, when we get them, the engine has already blown. This one had not. The outer gear of the pump had fractured into four pieces. I don't know how much longer it would have worked before failing entirely but it was clearly close to the end.
I thought we should pull the oil pan to check the bearings, and to my surprise we saw this laying in the pan. As you can see, the pan is otherwise pretty clean. The spots in the image are just bits of crud you see in any oil pan. There is no metal or evidence of damage visible. The oil is normal looking.
The crescent piece you see is the thrust face from the center main bearing cap. With no washer in place the crank moves back and forth a few mm. I think this is the original failure . . . I think the center bearing broke for some reason, the crank moved back and forth over a period of time, and that led to the eventual cracking of the oil pump gear.
Had we not caught this, the engine would have failed in the fairly near future. We will repair the bearing and time will tell how that holds up. I have some concerns because the crankshaft face may be galled. and that would ruin a new thrust face in short order. If we find that we face the choice of filing it in place, or removing the engine and essentially getting into an overhaul situation.
Now that I know this I realize we can check for the problem on an assembled motor by moving the crank pulley back and forth to check for excess play. I wonder how many more of these are out there, waiting to fail?