W210 (M104) - Check Oil Light on but dipstick level is fine.

[Ocean View]

I have a 96 W210 with the M104 engine.
From time to time I get a check oil light.
So After I let the car sit for about 30mins, I check the dipstick and it shows the oil to the top line. So I figured maybe this was because the oil filter drained during the wait and that the true level is about half a quart lower. So I added oil. Everything was fine. Drove the car for a few weeks and then another Check Oil level light comes on. So I check it and the level is now about half a quart above the top line. I am confused.
There is no dent or deformation on the oil pan from what I can tell.
By the way, the light does not always come on. Just once in a while.


Anyone have any ideas as what is going on?

[Ocean View]

I changed my oil and filter today and noticed that the oil was really dark.

Also I had more than the recommended 7 quarts due to me adding the oil from the previous week.
I am wonding if the light came on due to the oil being so dirty. I could not tell how thick it was but I imagined that it must have been as the color was really dark.
I added exactly 7 quarts as recommended and did a test drive.
No Oil light. Hope it stays that way.

[KenP]

I hope your light doesn't come back, but I suspect it will...
Time to start thinking about a bad oil level sensor.

[dtf]

How many miles on the engine? You need to check your oil level on an absolutely, perfectly level ground other wise you will get a false reading. If the car is pointed downhill and the dip stick says you're at the max line - in reality you don't have enough oil because it runs to the front of the oil pan.

[GVB]

You have a bad oil level sensor. Next service, just unbolt it and put a new one in, no big deal. I fhte light bothers you, unplug it.

[Ocean View]

Originally Posted by GVB

You have a bad oil level sensor. Next service, just unbolt it and put a new one in, no big deal. I fhte light bothers you, unplug it.

Yes, I think you guys are right about the sensor.
The light came on again yesturday. I checked on a flat level surface and my oil was at the max line so I know the amount of oil is fine.

I presume the oil level sensor is located in the oil pan.
Is this a fairly easy job for a basic DIY person or is this something that will take a lot of effort and time?

By the way, the car has 185,200 miles on it.

[GVB]

Remove the belly pan, after draining the oil, on the left side about 3 or 4 inches uo, you will see a sensor with a single wire to it, thats it. Take the two 10mm head bolts out, replace with new, and make sure a new o ring seal comes with it (check the box). Wont take any time at all.

FYI, when you change the oil, remove the oil filter first, the canister type oil filters can trap as much as 3/4-1qt of oil. Total system fill with filter removed before draining is about 9qt's

[Ocean View]

Originally Posted by GVB

Remove the belly pan, after draining the oil, on the left side about 3 or 4 inches uo, you will see a sensor with a single wire to it, thats it. Take the two 10mm head bolts out, replace with new, and make sure a new o ring seal comes with it (check the box). Wont take any time at all.

FYI, when you change the oil, remove the oil filter first, the canister type oil filters can trap as much as 3/4-1qt of oil. Total system fill with filter removed before draining is about 9qt's

Thanks for the info. Will try it on the next oil change.

[anthonyb]

I'm not sure if the W210 works the same way, but in the W124s there is a circuit in the instrument cluster that delays the oil low lamp until it gets a positive signal from the sensor for around 45 sec or so. This prevents the light from coming on and off during cornering, braking, or accelerating. When the circuit is busted, the light comes on whenever the sensor registers a low oil level condition, which generally results in intermittant warnings even when the oil level is fine.

[Ocean View]

Originally Posted by anthonyb

I'm not sure if the W210 works the same way, but in the W124s there is a circuit in the instrument cluster that delays the oil low lamp until it gets a positive signal from the sensor for around 45 sec or so. This prevents the light from coming on and off during cornering, braking, or accelerating. When the circuit is busted, the light comes on whenever the sensor registers a low oil level condition, which generally results in intermittant warnings even when the oil level is fine.

I will have to look into that.
If the W124 had it, I am sure the W210 has it too, no?

[GVB]

I have never come across this delay in the instrument cluster.
You have a bad oil level sensor. If the oil light will come on as soon as it grounds out, and it hold enough oil where it should stay above the low level light even cornering. But 1 qt low will turn it on.