ccryan67

I just finished installing a new air oil separator to include the centrifuge. After installing the new parts, I have a high degree of vacuum at the oil cap and am getting that loud chirping noise that is associated with a bad separator. The noise does not, however, go away when I open the oil cap. Any ideas what I did wrong and what I should look for once I go back in there?

cetialpha5

Did you use MB parts or aftermarket?

ccryan67

All MB from the dealership.

S-Prihadi

2012 is a M272 or M276 engine ?. The PCV valve is different.

If M276 PCV, I think the one capable of making noise is the diagram.



https://www.ebay.com/itm/114836794066 non genuine, diagram only.

PCV valve up close : https://www.ebay.com/itm/145069558067



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M272 PCV valve, I think its equivalent diagram is somewhere else on the engine.
https://www.ebay.com/itm/394233730467 non genuine as reference.



Whistling sound is like a restriction , so it is probably something to do with "diagram".

ccryan67

The engine is M276 and understood that the issue lies within the PCV system. That’s the basis of my question. There were no apparent restrictions on install. Given the centrifuge can only go on one way and there are just 5 bolts attaching the parts to the head, I’m not sure what could go wrong. But clearly something went wrong because it didn’t make this noise before and I didn’t have the extremely high vacuum that is now being pulled in the crank case.

has anyone experienced this issue after PCV/oil air separator replacement?

S-Prihadi

OK, next................

You replaced the SUCTION unit of the PCV system, item #30. Did you replace the "FRESH air" supply unit , which it seems to have also a valve.
These two work together as supply and demand , so that the water moisture and all baddies from piston blow by can be SUCKED back to intake manifold while not creating too much vacuum at the crankcase.




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Have fun on the 2nd try.

ccryan67

I replaced 80, 30, 10

S-Prihadi

Oh oh.... better check #80 valve, maybe stuck closed. It should be easily "open" I believe.
If your excessive vacuum gone when and if you remove hose #80 nipple at inlet before MAF, that means your #80 valve is bad. Try it.




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Too bad my engine is different, so I never mess with your #80 valve.
I have issue with my sort of equivalent #80 valve but since my engine is turbocharged and has positive boost at intake manifold at certain time, it is different in operation and I have secondary
oil vapor separator in the middle of the V-bank with kinda complex air hose plumbing to Bank 1 turbocharger inlet and V-block too.

S-Prihadi

I have to make correction for the test.
Item #80 has to be removed from the cylinder head if it is indeed blocked at the valve, so not it's hose end near ( before) the MAF to be disconnected.

ccryan67

Problem solved, I think. I had to replace the 80 vacuum line because I snapped it where it connects to the cylinder head. No issue there.

When I changed spark plugs at 120k miles, I had to replace the vacuum hose, not the hard plastic line, that goes from the intake to the brake booster. I bought the hose a little long and didn’t bother trimming it when I installed it. When reinstalling intake on this service, the hose got crimped and I did not seat it properly on the brake booster. That, apparently, caused the chirping noise I was getting under the hood. After correcting that issue, the noise went away but I still have what seems to be to be excessive vacuum when checked at the oil filler.

S-Prihadi

What value is your vacuum at the engine oil filler at idle ? What coolant temperature it was at ?

Here is my crankcase vacuum test.
https://mbworld.org/forums/e-class-w...sure-test.html

Its is about -35 millibar at idle, coolant temp at 81C which is not actually hot enough as normal operating temperature which should be 90ish C.