Does anyone have handy, or a link, to the M156 PCV diagram? Ideally, like other OEMs, it will show the flow paths under load/no-load.

Thanks!

 

PCV diagram is very simple. its only the PCV valve from the crank case to the intake manifold where folks tend to patch in an oil catch can. regarding the vacuum line diagram, it'll vary for each chassis, but for my W211, there is a brake booster then 3 small vacuum lines, and one medium hard line. 3 at the back and 1 at the front. the medium hard line is to vent fuel tank pressure is what i'm starting to understand.

 

No balance lines for the heads and CC?

Every engine I've ever seen has a routing to the intake manifold, and to the inlet; basically pre and post throttle body. This is to you're pulling maximum vacuum and drawing fresh air into the crankcase when not under load. The PCV valve is what switches from one loop to another; load/no-load.

Anyone have a FSM or system diagram?

 

there are no balance lines as after the before the throttle bodies and after the throttle bodies the two air streams merge into a plenum. all vacuum lines besides including the brake booster are fed in post throttle body so they're consistently seeing vacuum.

 

In all M156 engines, pressure is routed from the valve cover/cylinder head area and crankcase through the sump to the timing cover area where it enters a rubber breathing pipe that goes under the intake manifold inside the engine block and back to the intake manifold.



There are two variations of the M156 intake manifold and the breather valves.
1- Engines up to 60000591 Have a unique intake manifold part #. This was the original part on my ML63. In this configuration, crank pressure enters the intake manifold through two entry points:
A- Pre-Throttle body at atm. pressure regulated by the throttle plate position = Full load breathing
B- Post-throttle body at manifold vacuum open at all times = Part load breathing
As the diagram below shows.

My ML63 suffered from an increase in crankcase pressure. Oil dipstick would pop-out after load and oil would leak from the seals. Since the old-design breather pipe does not wear out like the newer PCV design, there was nothing to do but to replace the intake manifold to the newer design and use the repair solution 1560100270 Genuine Mercedes Benz - 1560100270 - BREATHER PIP (ecstuning.com)
This relieved the pressure dipstick popping and leaks are gone. The reason the old design is not sufficient is the small diameter of the part load pipe and the low vacuum for the full load pipe, since its at atm. pressure.

As for the newer design Post-engine 592


This design is simpler and requires the regular replacement of the PCV.
1- At idle, the high vacuum keeps the PCV shut, preventing vacuum leaks and flow.
2- At part throttle, the PCV is partially open.
3- At full load, the PCV is fully open.

 

Thanks so much for that info! That what I was looking for, and more!

Odd how they went to a limited system on the later engines (C63/M156). This means no fresh air is drawn into the crankcase to evacuate blow-by gasses, and no vacuum is applied to the crankcase, under low load conditions.

Odd choice I've never seen made by a manufacturer before.

 

my E63 has a 5/2006 production date and it doesn't have the dual feed breather. unless it was retrofitted some how?

 

Maybe the initial variation was for the 164/251 only, or as you said, the intake manifold and the repair solution could have been installed earlier at some point.