question regarding oil pressure/air injection - PeachParts Mercedes-Benz Forum

lsmalley · #1 12-24-2010, 10:55 PM

my oil pressure only gets up to about 2.8 bars when I'm at about 2000 rpm and is at 0 if I'm idle or just going about 10-15 mph.....basically when I'm not giving it gas. How dangerous is this? I just bought a new oil cap, I'm running 20w-50, oil filter is new, and I haven't noticed any huge leaks of oil? could low oil pressure be attributed to the sending unit, even though I do notice the pressure gauge working some? also, I am constantly getting error code 11 and sometimes 16. what do I need to fix or replace to rectify these?

ps2cho · #2 12-25-2010, 01:03 AM

You really need to figure it out ASAP. You should be 1.5-2 bar idle and at the stop at partial/full load.

Get a mechanical gauge on it to determine if the sending unit is bad or not.

lsmalley · #3 12-25-2010, 01:12 AM

mechanical gauge? what is that and how do I determine if its bad? and if the sending unit is bad does that actually control the oil pressure? or does it just interpret the pressure? because if its bad and it only interprets the pressure, I could be getting false readings and my pressure may be fine.

tbomachines · #4 12-25-2010, 01:19 AM

Since the sending unit uses an electronic signal to decide what to display on the instrument cluster, using a mechanical gauge will rule out any electrical funkiness.

http://www.harborfreight.com/catalogsearch/result?category=&q=oil+gauge

Here are some cheapo ones. If your car is running okay, chances are that it is the sending unit or the gauge in the cluster that is out of whack, but it is not something to mess around with by any means. Your other option is to replace the gauge itself or sending unit with known good parts. But I would guess picking up a mechanical gauge and checking that way is much less of a headache and cheaper.

lsmalley · #5 12-25-2010, 01:39 AM

car, runs great and no weird noises, except for some suspension noises. Is the oil sending unit also called the oil level sender? because that is what I'm seeing on fast lane. also, any comments on the other issue I mentioned regarding the air injection system?

Ferdman · #6 12-25-2010, 04:34 PM

The oil level sensor and the oil pressure sending unit are two different things, as indicated by their names. The oil pressure sending unit does not control oil pressure, but simply sends a signal to the dashboard guage that indicates oil pressure. It's likely the sending unit is bad, so measure the oil pressure with a mechanical guage to confirm the actual oil pressure. If the oil sending unit is bad replace it.

The oil level sensor is mounted on the side of the oil pan and illuminates a red warning light on the dashboard when the oil level is too low.

lsmalley · #7 12-26-2010, 06:20 AM

yeah the oil level sensor works fine. and I know exactly where the oil pressure unit is. so I will get one of those. since the pressure gauge to check the pressure and the sending unit are about the same price. I'll just get the sending unit and save myself $25. Besides, no harm in replacing a 20 year old part anyways.