How can you tell if your oil pump is going bad?
 

Hi Folks,

The low oil level warning light comes on when the car gets to about 60mph, and stays on. I've checked the oil and it the level seems fine. I'm off to have the oil and filter changed, but wanted to find out how I'd know if the oil pump were going out. I've never experienced that. Does it make funky sounds, would the pressure be all over the place?

Maybe it's just the oil level sender unit?

Should I be really worried?

Thanks everyone,

Craig

What car? How many miles? What does your oil pressure gauge say? How low is the oil level?

Its hard to tell if we don't know what kind of car we are talking about.

What is the oil pressure guage showing when the light comes on?

I edited his post to show his signature, which tells which type.

An M117 should PEG the oil pressure gauge at almost any RPM above idle. If you aren't pegged at, say, 1500RPMs, something is wrong with either the sender or the oil pump.

There are TIMES when my m117 will NOT have pegged oil pressure at high RPMs. If I am going around a VERY sharp corner and go into another at VERY high speed, it will fluctuate for an instant. That's the only time mine EVER drops below pegged at speed.

If your gauge isn't pegged at speed at all times, then it's time to worry. Otherwise, it is probably a faulty level gauge.

Oil pump problem...
 

I should have been more clear on my original post...

1991 560SEL...

The oil level in the car is fine, in fact I probably have a tad too much in the oil pan. The oil pressure gauge itself is fine. A steady 3 at higher speeds, dropping to around 1.5 at idle.

The problem is just that the Low Oil Warning light comes on and stays on when I hit 60mph. It goes off again as soon as I drop back to lower speeds.

I don't know if the oil pump is not working hard enough to put oil through the case, or if its probably just the oil level sending unit.

I think that makes more sense.

Sorry,
Craig

Answer:
 

Either the sensor or wiring is damaged.
There is a 50/50 chance the engine mounts may be bad also.

MB Wiring Harness Failure
http://www.peachparts.com/shopforum/general-information/128181-mb-wiring-harness-failure.html#post927185

you need to drain out some oil so it is not overfull.

i inadvertantly overfilled my 603 turbo and this was the result. the crank whips up the oil and it reads low.

actually now that i think of it my car would run a bit hot, but i suspect you still may benefit from letting out some oil.

the reason they have an oil level warning light in the newer benz models is that they have made the engines shorter and instead of having extra room in the pan for a little leeway on level it is all very tight. overfill it and the rod throws drag in the oil. whipping it up and generating extra heat.

try that before spending any money. imho

tom w

The sensor is probably bad. All that is, is an idiot light telling you when your oil is at or below the min mark on the dipstick. Their is a little float in the oil pan. Clean the connections and see if it goes away, if not the float is probably bad. Simple to change during an oil change.

Oil Level Warning light on 91 560SEL
 

A mechanic that I'm starting to trust told me to change my oil, because the oil was too old and running hot, which causes the Low Level Warning Light to come on. Took it to a dealer (not MBZ dealer) to have the oil changed, but I put in 20/50. Don't know why for sure, just did based on what the guy (who was about 14yo) said.

The light stayed off for about two days, and then started coming on again when I hit 65 or so. It goes off as soon as I go below 65. The oil level is fine, by the way.

So, I'm assuming its the floater, or the sender unit - both of which are cheap and easy (my favorite) so I'm going to replace them and see what happens.

Anyone think I'm really dumb for listening to the pre-pubescent oil change guy and putting in 20/50?

Craig

Answer:
 

Install an oil pressure gauge between the oil level sender unit and mounting boss to cross check the accuracy.

Aftermarket instruments - GAUGES
http://www.peachparts.com/shopforum/mercedes-benz-performance-paddock/159332-aftermarket-instruments-gauges.html#post1224068

i dont see a problem with using 2050 oil.

is it within the book recommendation?

although my 84 500sec sticks a hydraulic valve lash adjuster if i run 15w40 in it and is fine with 10w30 mobil 1.

tom w