Oil Light?

E28 technical advice asked and given! Troubleshooting, modifications and more.
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smackmybutter535i
Posts: 426
Joined: Feb 12, 2006 12:00 PM

Post by smackmybutter535i »

When I start my car the oil light comes on for about 5 seconds then shuts off, what would be causing this? Is it just the sensor or something I should worry about?
booker
Beamter
Beamter
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Joined: Feb 12, 2006 12:00 PM
Location: New Orleans

Post by booker »

[QUOTE="smackmybutter535i"]When I start my car the oil light comes on for about 5 seconds then shuts off, what would be causing this? Is it just the sensor or something I should worry about?[/QUOTE]

If it's the one in the cluster, you're OK. It takes a couple of seconds for the oil pressure to build when you first start the car. If it is worrying you, you can clean, or replace, the sensor. It is in the head at the back of the engine.
al525i
Posts: 662
Joined: Feb 12, 2006 12:00 PM

Post by al525i »

its a common issue on older/higher mileage m30's. whats happening is the oil is draining back into the block on shutdown and the 5 second or so delay is the time it takes for the oil to pump up to the pressure sender. The oil has to go all the way from the pump in the oil pan up to the sender in the back of the head which takes a decent time. sometimes changing the oil with something slightly thicker will help but usually it just happens with time and the best advice is not to rev the engine for a few seconds after the light goes off to give the engine a chance to properly oil itself.

hope this helps
booker
Beamter
Beamter
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Joined: Feb 12, 2006 12:00 PM
Location: New Orleans

Post by booker »

[QUOTE="smackmybutter535i"]-I'm a newbie, help me out on what to do next for the best bang for a buck [/QUOTE]

No doubt in my mind, a 3.73 LS differential. Wake that puppy right up. About $250...
Tammer in Philly
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Location: CHI, IL

Post by Tammer in Philly »

Don't worry unless it takes more than 9-10 seconds to go out. And Al, I believe that thinner oil, not thicker, will make it go out faster on a cold start (flows through passages faster when cold), but I wouldn't change my oil viscosity just for that purpose.

In an off-topic callback to a Roach thread about oil :-), we were discussing viscosity (of blood) in my clinical metabolism class, and despite the presence of cells and numerous biomolecules in blood, it follows pretty much the same viscosity parameters as oils. Discussion was centered around the relationship between hypoxia and a ruddy complexion.

-tammer
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