Hi all, Last weekend I swapped my crankcase vent valve and separator. I was prompted to do this by the oil in the airfilter housing and the vacuum on the engine when removing the oil cap.

From what I had read the issue is that crankcase vent. This was a major PITA to replace, but not impossible. Took me about 5 hours. I highly recommend purchasing an e10 ratchet wrench and and a set of non impact Esockets. (Female torx) It also would have been good to have the correct range of torque wrench. My inch pounder did ok, but was almost maxed out, and the other one I had was at the minimum end of the range and so not really accurate.

I also replaced the timing chain tensioners and installed check valves. The checkvalve press was $14.50 on Aliexpress, and only took a couple of weeks or so to get here. It worked perfectly.

Unfortunately after putting it all back together I found that the crankcase vacuum condition was still present. It doesn't seem to cause any issues. Should I be concerned? Is there another common cause?

As an aside the timing chain tensioners and check valves almost immediately resolved the rattle that I was experiencing

I did discover that my cam sensors are leaking oil, so I'll have to pull the upper intake again to swap them out once they arrive.

Altogether it was a 9 hour day, time well spent.

Cover the intake

Checkvalve press $12 on alliexpress

 

PCV while its name is Postive Crankcase Ventilation system, the actual working is your intake manifold is supposed to suck those bad piston blow-by air the PCV is managing.
Thus your engine will have and MUST have mild vacuum reading at the oil filler cap or the oil dipstick level.

Read here : https://mbworld.org/forums/e-class-w...sure-test.html

I would think minimum you must get at idling and proper engine operating temperature, minimum 20 millibar.

 

Thank you for your reply!

I'm not sure how much vacuum is on it, but it's definitely more than any other vehicle I've ever owned. It is enough to be noticeable when I remove the oil cap. I'll have to setup a vacuum gauge to measure it. and thanks for the link I'm digging into that further.

 

so your post from the link was very informative.

From what I can gather from your post normal vacuum is roughly 50 mbar or 0.73 psi negative.

I'll have to verify this later, but the oil cap opening is roughly 1.5 inches diameter, that is 7.07 sq inches (pi*r^2). Just guessing that it took no more than 1.5 pounds of force (from my calibrated arm) to break the seal. So 1.5/7.07 = 0.21 psi negative. I'll have to verify all of this, but it seems like I'm in spec.

It's just a little surprising to me given I've worked on a variety of cars over the years and never remember any force required to break the seal on an oil cap for any engine of any type.
Anyway thanks for taking the time to point me to your post.

 

Area = pi * RADIUS^2 = 3.14 * (0.75*0.75) = 1.77 sq in

 

I would say my engine at warm idle is -35 millibar gauge value, there about.
Too bad MB does not produce/share vacuum values of cranckase in their WIS.
The intake manifold itself at idle, when vacuum at oil dipstick being -35 millibar gauge, is at 369 millibar absolute or -681 millibar gauge.

My home being at sea level and fair weather , the barometric pressure would be 1,013 millibar.

Depending on how the PCV is hooked up to intake manifold system and also fuel vapor purge system ( EVAP ),
at idle any gasoline engine using throttle body would produce vacuum reading.
Here I do not know how much "air" is provided by EVAP system on mine, but I believe if the EVAP solenoid is stuck closed, it may produce higher crankcase
reading as it is an "air" source afterall, albeit a controlled one and not 100% open all the time.

BMW N55 engine is a bit different as I read, while it has throttle body, its air intake opening management is not using throttle body, but rather its valvetronic.

Maybe that is why it has higher than my M276.8 3.0 Turbo , at -50 millibar ( +- 8 ) as stated value.

However, a turbocharged engine like mine when at boost, the intake manifold is at positive pressure above ambient and there comes a more complex
PCV system MB will call as high load and low load.
My PCV system has injection port into RIGHT BANK turbocharger suction side too #2 of image below ( no check valve ) and another injection
port at intake manifold #71 & #1 ( #71 has a check valve ). #2 is the FULL LOAD aka boosted, #71 & #1 is the low/partial load aka boost not build up yet.





I want to share a story. It is of M271.8 EVO 1.8L Turbocharged inline 4 engine found in W212 E200/E250 gasoline. Also in W204 C200/C250.
I could not get higher than -3 millibar crankcase vacuum at warm idle, while all PCV system is new already, up to the plastic cylinder head cover which is part of the PCV system.
I need to run a compression test and leak down test on that engine, for my own learning, and I am still waiting for a good spark plug adapter to do the test.
This is a 94,000 KM engine of year 2010 , I fear it has high piston blow-by. When the oil filler cap is opened, its air output seems a lot instead of good suction.
If I can sort out this M271.8 engine, as I believe I need to see -20 millibar at least ( reference is BMW N20 at -35 millibar ), I will share the information here.
It is a pain in the azz when MB does not produce crankcase vacuum values in their WIS , it does not help us troubleshooting....duggghhhh !!!

 

This is what I get for trusting google to do my math for me. Thank you for the correction.

So if that puts me at 0.847 psi negative, which is a little high, but would be in the margin of error given my guesses at the values and my apparently poor math skill. So Maybe I'm right on target.

Thanks again for pointing that out.

 

It definitely would be nice to have the spec. Aside from this though WIS has been invaluable for me to do this job correctly.