QuestionI have a 2004 Discovery which works and runs perfectly except that the oil engine light turns on when the motor is idle, once you rev up the motor the engine oil light goes out. I already changed the sending unit, oil pump and timing cover. The pump pressure is good except when the motor is idle. I opened up the oil pan and the motor looks great, there is strong compression, no blow by and no indication on any damages, the bearing looked brand new.It is a big mistery since the motor works really good. I checked all of the electrical areas and they look fine. Am I missing something???
AnswerWell, you must be missing something. What other answer could there be given that description? If the light is right, the oil pressure is low, and if you don't fix it, you will have premature engine failure. If the light is wrong, it's a wild goose chase but you need to know which answer is true.
First I would use a screw in gauge to ascertain the oil pressure at the time the light comes on.
Assuming the light is right I would check the timing cover, then the bearing clearances, then the cam galleries. There must be an answer, and you need to find it if you want the truck to last.
There have been some motors with alignment problems between the front cover and block drillings that interfere with oil flow, but those problems usually produced pressure trouble right from new, not 4 years later.
Some blocks had a plug that fell out of the oil drilling for the cam. You have to strip the motor to find that.
