Re: Oil Guage - sending unit issue?

Over the last 2 months I'm getting what seems to be random results when checking my oil. I follow the same protocol each time - let the engine warm up and make sure the car is level. Each time I get +/- 2 bars on the reading from the time before.

This morning a got a low level reading with a flashing warning (not a low level "alarm" on the instrument cluster). So I added just shy of a liter, gave it time to drain down, and checked the level again - this time it read at the maximum!

I really miss the old reliable dipstick.

Anything else causing the problem besides a bad sending unit?

TIA,

Ed

Ed from Long Island (Tampa)
05S Cobalt/Blue/Blue

Quote
Ed fromTampa ( formerly Long Island)
Over the last 2 months I'm getting what seems to be random results when checking my oil. I follow the same protocol each time - let the engine warm up and make sure the car is level. Each time I get +/- 2 bars on the reading from the time before.

This morning a got a low level reading with a flashing warning (not a low level "alarm" on the instrument cluster). So I added just shy of a liter, gave it time to drain down, and checked the level again - this time it read at the maximum!

I really miss the old reliable dipstick.

Anything else causing the problem besides a bad sending unit?

TIA,

Ed

Has the earmarks of a bad sensor. The sensor is a bare wire in a narrow loop that is inside a plastic tube and arranged so the bare portion of the wire is immersed in the oil. A level check consists of sending an electric current through the bare wire and how much current is measured at the other end is used to calcuate (look up in a table) the oil level.

If this wire breaks there is no reading, but it is a pretty substantial wire. While not that large in gage it is made of a some mighty impressive metal, ni-chrome or something similar. But if this wire comes loose from the plastic hook at the bottom of the tube while the wire can't escape the tube it can move about inside the tube some and this can account for the varying readings.

If this has happened then and you add oil based on this erroneous reading you can (will) over fill the engine with oil.

Unless things have changed with the newer models my info is the way the oil level unit is tested/confirmed operating correctly is a by the book oil service is done which cumulates with a known quantity of oil added back to the engine and at this time the reading of the sensor should agree with the known quantity of oil. My info is the reading should read at the max line level and not over or under.

The "old reliable dipstick" was/is while certainly old not all that reliable. And too inconvenient to be used all that often. How many times when you are filling up your car's gas tank do you actually see someone get out and check the oil level using the dipstick? When I had my VW Golf and later my GTO both which had a dipstick I'd check the oil level and I never recall seeing anyone else checking the oil level. When filling up my Porsches and looking around at others getting gas I seldom and I mean seldom as in practically never see anyone checking the oil level. Most while filling up are on the phone. I keep a sharp eye out in case the driver gets in the car and forgets the nozzle is still in the tank filler tube.

Thanks Mark, I'm due for an oil change and will see what happens.

Ed from Long Island (Tampa)
05S Cobalt/Blue/Blue