QuestionWe have a 2000 Land Rover Discovery Series II with 80,000 miles. two weeks ago, after having a water pump replaced, we found that after driving about 20 miles, the low oil pressure light comes on when the engine RPMs drop below 1,000. The engine oil is a 10W40 synthetic. We've had the oil changed twice last week and engine cleaner run through between the changes. What are the most common causes for this indication?
AnswerHi Roger,
My first thought was to check the oil pressure sending unit. Since you ran engine flush twice thru your Disco, maybe the sender is fouled and needs some cleaning too. It would have to be removed and cleaned up a bit. This can send false readings after being battered with gunk flushed thru your engine. ITs the cheaper and easier solution I can think of.
Another owner had a similar complaint with his Series I Disco: an oil pressure check was performed and the result was very low pressure (less than 10psi). They checked over and serviced the oil pump, which was fine. They did find a mass of gunk in the base of the sump, which would appear to have been blocking up the oil feed.
Once drained, the sump was removed, both sump and oil feed pipe cleaned, nothing major and he was back on the road.
You may have to measure the oil pressure when the engine is running and at around 2500rpm. Full pressure (whatever it is for your engine), should have been reached by then.
IF it is then the oil pump is OK.
If could also be the relief valve and perhaps other followers are failing. A rebuild is the correct method to repair this and avoid a possible engine seize.
So, have your mechanic perform an oil pressure test to determine if the oil pump is at fault. Remove your oil sump to see if the oil take up feed is blocked or fouled.
Best of luck,
JohnMc
