190E 2.6 oil warning light illuminating

chrisd87

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Tl;dr - would an oil level ~4/10ths of the way up the dipstick cause the oil warning light to illuminate, or is something else wrong?


Hi everyone,

When driving home yesterday in my 190E 2.6, to my horror the oil light came on. As quickly as I could, I stopped the car and shut down the engine, and upon restarting the light went out. However, a few minutes later the light came on again. This time I continued driving, and the light would come on for a bit, go out for a bit, come on again, etc. I presume that the warning light was concerning low oil level, since the oil pressure on the gauge remained normal at all times.

When I got home I checked the oil level, which is probably 4/10ths of the way between the red sections on the dipstick - slightly below the level it was when I checked it about a week ago. Is this the sort of level which would normally activate the warning light? I would have thought that the warning light would come on only when the oil level was very low indeed.

This makes me concerned that there might be something more sinister going on. When I got home and turned off the engine, I left it for a minute or so and withdrew the dipstick. There was only a small amount of oil on it, right down near the minimum mark. About an hour later, I rechecked the level and it was 4/10ths of the way up the dipstick. I've never timed how long it normally takes for the level to settle, but I don't remember the level being quite as low as that when I've previously withdrawn the dipstick shortly after stopping the engine.

This makes me wonder if the problem might be a partial blockage in an oilway, preventing the oil from returning to the sump properly, which is causing the level to drop.

By way of background, the oil (Shell Helix HX7 10W/40 semi-synth) and filter (genuine MB) are about 5 months and 2500 miles old. The oil was changed 12 months and 4000 miles prior to that. Prior to the latter change (performed shortly after I purchased the car) it clearly hadn't been changed for quite some time, as when drained the old oil was absolutely foul - very black and a bit smelly.

It's this last fact that makes me worry that the engine may have some sludge in it, which could be causing a blockage.

My current plan is to top up the oil to the full mark and see if the problem goes away. If it doesn't, would using an engine flush product (and changing the oil) be a good idea? I'm always a bit wary of using them on an old engine for fear of causing leaks, particularly given that the oil tightness of the M103's head gasket is a known weakness.

Many thanks for any help/advice, etc.
 

herby thr cls

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if the oil pressure gauge was still reading OK your problem is with the oil pressure light sender, this is a small unit that screws into the engine block and its job is to bring on the warning light if the engine loses oil pressure, I have had this switch pack up on 2 of my cars over the years, the switch will cost you no more than £15 and it is a simple DIY job
 

stwat

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if the oil pressure gauge was still reading OK your problem is with the oil pressure light sender, this is a small unit that screws into the engine block and its job is to bring on the warning light if the engine loses oil pressure, I have had this switch pack up on 2 of my cars over the years, the switch will cost you no more than £15 and it is a simple DIY job

These cars don't have a low oil pressure light. The pressure gauge is used to monitor pressure. The warning light is simply a low oil level light which starts to illuminate when the oil gets to below half way on the dipstick.
 

herby thr cls

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ok, thanks for that info Stwat, I thought that it was a pressure warning lamp as well.
 

stwat

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The later cars do indeed have a low pressure light but the earlier cars with a pressure gauge just have a low oil level light.
 

rorf

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If the oil before was bad I would change the oil and filter again for peace of mind which should get rid of the last remnants of sludge and gunge. Keep the oil level between the full and min mark (half way mark), I believe not keeping the oil level at max stops the engine from developing oil leaks - over filled engine causes more problems than under filled.
 
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chrisd87

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May 29, 2013
Messages
32
Car
190e 2.6 / W123 230 / W123 230E
I've topped the oil up and the light has stayed out, so I think this one is solved for now!
 

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