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Just noticed that my oil separator looks very oily.
I don't really know what it does or the symptom of a bad oil separator. The engine has a very rough idle but I know one of the motor mounts needs change. Can a bad oil separator contribute to the rough idle also?
A separate side question to anyone who is kind enough to answer. How do you tell the supercharger is functioning as expected? I ask only because I never really feel the "power" of a supercharged engine.
Last edited by ihaveaquestion; Apr 23, 2020 at 09:02 PM.
Sound like you might have a clogged PCV check valve. It's located on the bottom of the intake manifold. It's supposedly a PITA to get to because you need to both the intake and exhaust to get to it. Here's a few threads about it. You can find quite a few if you search for it:
The oil separator rarely clogs. Usually it's the PCV check valve. MB, like most cars, uses two types of crankcase ventilation: full-throttle and part-throttle/idle. Your photos show the former. At full throttle, the vacuum in the intake manifold pretty much much equals that just past the air filter. Since there's not a lot of vacuum the tubes to get rid of blow-by gasses are larger so pressure doesn't build up in the crankcase. The part-throttle to idle parts consists of a connection between the intake manifold and crankcase that sucks blow-by gasses directly into the intake manifold. It uses a precisely-sized restricting hole that is programmed into the ECU. This vacuum in the intake manifold is more than enough to suck out blow-by gasses at idle and the engineers took advantage of this: the full-throttle parts now work in reverse, and let fresh filtered-air into the crankcase to help keep your oil clean.
Things get a little different when a supercharger is added. When the supercharger is on the intake manifold no longer has a vacuum in it; it's pressurized. That means that without a check valve (which the C230K has) this pressurized air is going to be blown into crankcase, and the oil separator. That's most likely why your seeing the oil stains on the engine. You can also look inside your intercooler. If the check valve has failed, there will be oil there. It's really a check valve, not a PCV valve, even though it's called a PCV check valve at auto-part stores. It shouldn't cost more than $25.
I guess these parts are interconnected somehow. But why not just a failed oil separator?
Do the simple tests and checks first.
Check for the following and report back.
1) Oil contamination in the air filter housing, at the bottom end (lowest point inside and the filter itself.
2) Open up the MAF on the intake side of the hose that connects to the MAF - check for oil film contamination.
Oil contamination in the MAF intake hose can affect the performance and Kompressor.
If your oil separator isn't functioning correctly, any of the oil fumes will go into the air filter housing rather than thru the hose back into the crankcase to be re-purposed (for emission control purposes.
Replace it, and its hoses - they get brittle over heat and time. Optionally, if your State permits it, you can bypass the hose that goes into the air filter and vent it into the atmosphere. (plug up the intake connection on the AF box where the oil separator hose attaches into the AF box.
There is plenty of write-ups on this topic in the w202 and R170 forums for improved reliability and performance (w202 and R170 share the same Kompressor motor)
They DONT CLOG UP per se, they malfunction and when they do malfunction, they don't circulate the oil fumes correctly into the correct hose line (back into the crankcase). Instead they vent the oil fumes/film in the AF box where it collects in the form of an oil film and oil. From there, it goes thru the Kompressor and circulates to the MAF. Not fresh air, but oil contaminated air.
An oil film builds up within the intake hose and contaminates the MAF sensors giving your mis-read air readings (due to oil contamination) leading to sluggish performance, acceleration, sputtering etc.
The air filter and the box are bone dry. Checked the underside of the upper box too.
Not sure which the MAF intake hose is but I checked the hose connected to MAF from underneath and it's bone dry once again. I ran my finger inside the hose and didn't feel any oil at all.
The rough idle was fixed by replacing the motor mounts, so that's no longer a problem.
I seem to recall seeing oil in the chamber where the ignition coils are but that was a few years back. Does that have a connection with the oil separator?
Last edited by ihaveaquestion; Apr 29, 2020 at 10:36 PM.
Have you scanned for any saved codes. If any, post here.
OK, so no oil film. That's good. Check the hoses form the OS and clean them out making sure they are clear. If they feel look ok with no cracks, no need t replace them.
I would remove your MAF and clean it with CRC maf cleaner and reassemble.
Before you do this, unplug the MAF and drive it around. Feel and see how it operates vs. when it's plugged in.
Make a good note if it.
When the MAF is cleaned and reassembled, plug it back in and drive it around and "feel and see" how it does vs. before.
Are you getting any boost when you hit the throttle? (ie. any passing power)
EDIT:
clean up the EC. It's horrible and makes it difficult n messy to work under. (just my 2 cents)
EC stands for? Probably something easy to figure out but I have had a few drinks tonight
No code last time I check. Will have to check again but I doubt it.
So if I disconnect MAF as shown in the pic would that be sufficient to test it? Or need to be disconnected from the upper hose too? Essentially there will be a gap between the two hoses where the MAF is at ?
I mean the car drives fine now after the motor mount replacement. But the oily oil separator seems to suggest there is an issue.
I should clarify, disconnect the plug to the MAF (keep the MAF hose assembly installed) and see how it runs.
The oil separator is a cheap part as are the hoses to it. I replaced all of mine, and went further - vented the hose line that typically goes into the AF box by extending this hose down into the EC right below (where the OS is located) on the same side. We dont have emission inspections up here anymore.
I would clean it all up (the oil) on the exterior of the OS and area, and monitor it, if you dont need to spend the $ on these replacements.
Well, I got check engine light, major shaking and the engine actually killed itself the first time I put it in Drive.
No noticeable difference in engine response when the car runs. I won't be able to take another look at the car since it's in the shop for one week for body work.
Well, I got check engine light, major shaking and the engine actually killed itself the first time I put it in Drive.
No noticeable difference in engine response when the car runs. I won't be able to take another look at the car since it's in the shop for one week for body work.
After you pulled the connector off the maf?
And what do you mean "noticeable difference.." Which is improved, before pulling or after pulling.
You need to be more precise when you answer and make statements please.
The Haynes MB C-Class Manual has probably the best illustrations I know of showing how the two-stage crankcase ventilation works, but I don't believe its OK to post them. They call the stages idle speed to mid-part load and upper-part load to full load. It shows a non-Kompressor system but the only difference is what they call a restrictor is a check-valve in the Kompressor. What can happen is that blow-by can clog up the restrictor, or check-valve, over time. On a non-Kompressor engine it might go unnoticed since the upper-part load to full load side will still vent any blow-by into the airbox. On a Kompressor the check valve could fail to close when boost builds up in the intake manifold and send boosted air into the crankcase, overwhelming the oil-separator, and give the oil contamination you describe
Now that I got my car back, I got to do another test run today.
With MAF unplugged, I notice slightly torque and the engine runs smoother. It makes more of a supercharged sound "Whoooooph".
With MAF plugged in, slightly less torque and slightly rougher but makes more of a grunting sound. I feel the car runs a bit "faster" with MAF plugged in.
Now that I got my car back, I got to do another test run today.
With MAF unplugged, I notice slightly torque and the engine runs smoother. It makes more of a supercharged sound "Whoooooph".
With MAF plugged in, slightly less torque and slightly rougher but makes more of a grunting sound. I feel the car runs a bit "faster" with MAF plugged in.
Doesnt seem to be bad maf.
Has the MAF ever been replaced?
Get access to a scanner and scan the live STFT and LTFT.
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