S-Prihadi

Gents,

I got itchy hands , ever since my friend's M271.860 1.8L turbo engine has a bad Low/Partial load PCV system clogged and causing fuel dilution into the engine oil.
I posted here , at post #1,397 https://mbworld.org/forums/w212-amg/...ml#post8949634

Now I am curious on how M278 and M157 PCV works.

The M157 or M278 booklet is not very clear on the overall PCV system which the booklet does not include fuel vapor injection port into the intake manifold.
The booklet also failed to indicate that the intake manifold has back-up redundancy vacuum port* ( * or a boosted port when turbo kicks in ) for brake booster vacuum.




.......................
Pay attention to Port #1, 2 and 3 in green, above image and in red for below image.
.......................











Port #1 works like this :
Vacuum pump gets hose end with check valve A >>>>> Port #1 of intake manifold gets hose end with check valve B >>>> Brake booster gets ordinary hose end, no check valve.

The Port #1 hose assy is like this :
Yes, never trust a 100% parts shape drawing in EPC compared to the actual hose. For a few hoses, including coolant, the drawing is so bad, it is misleading.










Vacuum pump gets hose end with check valve A >>>>> Port #1 of intake manifold gets hose end with check valve B >>>> Brake booster gets ordinary hose end, no check valve.

The failure of check valves A and B and when engine is under boost, will cause brake booster to be full of positive air pressure, instead of vacuum negative air pressure.
So basically you loose boosted brake. At the same time, the vacuum pump looses its vacuum too, and turbo boost can drop down as there is not enough vacuum to pull the vacuum actuator of the waste-gate,
because the vacuum pump driven by LEFT bank intake camshaft is like a big leaky vacuum pump. Here , that small silicone check valve at the vacuum pump small port, can fail too by boosted air pressure inside vacuum pump.
This one : https://mbworld.org/forums/w212-amg/...ve-repair.html



Also the engine intake manifold will loose part of its turbo boost wasted to brake booster and vacuum pump
To what extend positive pressure air into engine crankcase from the failed check valves A & B of hose assy at Port #1 will cause crankshaft and camshaft seal leak...I don't know.

I don't understand why MB does this way for M278 and M157.
My M276 3.0 Turbo is very simple, brake booster is direct vacuum powered by the vacuum pump, no sharing to intake manifold .
The turbo waste-gate vacuum actuator is the same as M278 and M157 including the boost control solenoid.

====================


Port #2 :
This is fuel vapor injection into intake manifold at Port #2, so there is a check valve at the hose assy too. The solenoid of fuel vapor is a normally closed type.




That bulge is a check valve



=====


Now Port #3
The PCV "system". Its check valve can fail too.



.




So when your replace your PCV system /centrifuge , those 2 hoses I mentioned for Port #1 and #2 has to be renewed too as preventive measure.

Good luck on your maintenance.

Cifdig

Two questions . Does he have intakes, And did he unplug the solenoid if so how long .
not that it's the issue . Just wanna get all variables. So I can tell you what I know so far

Cifdig

I know this unit intimately, far beyond the thought of how it works . I know how it works and how to improve crank case ventilation .

Ultrakla$$ic

SUB'd...........I too have been racking my brain on how this PCV system works. I want a catch can setup but I want it to be EFFECTIVE and the ones on Youtube are sketchy at best.

S-Prihadi

I am assuming you are asking about my friend's baby 4 cylinders M271.860 ?
I dont understand the one in blue , I mean all engines must have intake, as in intake manifold.
In green, you mean OIL PUMP SOLENOID defeat ? This baby 4 cylinders M271.860 has traditional oil pump, no solenoid control for 2 stage pressures like M276, M278 or M157

S-Prihadi

When an engine is turbocharged, the PCV system design is much more challenging than an N-A engine.
At times we have boost ( above ambient pressure ) at intake manifold, not vacuum ( below ambient pressure ) only a 100% of the time like N-A engine.

So check-valves must be employed everywhere any PCV system injection hose is connected to a "boosted" intake manifold.
Check valves will fail over time, more so when it is oil soaked due to PCV system poor or not so good oil-vapor separation.

So we need to figure out all "injection" of piston blow by air aka crankcase air or fuel vapor hoses into our boosted intake manifold , find their check valves and inspect them.


I have to make number correction : Sorry for the previous typo.
I also added ATM or Atmospheric Pressure section of the PCV, labeled ATM in orange. This means this zone has no boost, always suction or vacuum like an N-A engine.





Left BANK oil-vapor separator, item 13.




Right BANK , this one comes from the centrifuge/PCV





If one wants to check check valves integrity, pump it 1.3 times the turbo boost your engine has and see how slow or fast its leak is or no leak at all.



My M276 3.0Turbo engine PCV system is the most elegant , and oil free at intake manifold and simple compared to M276 3.5NA and M278/M157.
MB understood its simplicity, as such I must buy complete assy and can't buy only the centrifuge side.

I must buy this complete assy



And this one, item 150 in blue : Where the duo check valve is.




.





Here is M276.820 3.0 Turbo PCV system peek for its duo-valve

The duo check valve item 71 above, its top side check valve section facing windshield or flywheel is for oil vapor or crankcase air
Its radiator facing check valve section is for fuel vapor.






.



When not under boost, it is then under vacuum




When under boost, check valves block positive pressure from escaping the intake manifold.

Ultrakla$$ic

SO, in reference to these two pics here that demonstrate parts on my m278 engine you pretty much confirmed that THIS guys catch can setup is appropriate and highly functional in keeping my intake manifold LESS oily on my m278 engine with his catch can placement and setup correct??

S-Prihadi

I can't comment much on the video's Catch Can, but I can tell you how oil and vapor separation can work well.

The key is centrifugal spinning action.
Oil being much heavier than vapor/gas will be spun out.
Hence MB has that centrifugal unit, they call OIL DRIP PAN.



This Oil Drip Pan aka Centrifuge P/N A273 010 01 62 is used also on M272, M273.

Catch Can is air flow diverter device, its design hoped the sudden change of direction of oil laden air, will make the heavier oil hit a designed obstruction and ended up at the
bottom and the vapor/air is then cleaner when sucked by intake manifold. Sometimes they rely on the oil laden air flow to hit maze kind of zig zag obstruction, hoping for the same result.

However, nothing can beat centrifugal force when it comes to separation of water from fuel or oil from oil laden vapor.
The heavier the weight difference between the 2 stuff it wants to separate, the better the result is.

See here the vent holes of the oil drip pan.
That is how the liquid oil in RED which is heavy get thrown out and super light weight less oily air/vapor/gas in GREEN will then be sucked by the intake manifold.



.



Here is an animation you can use to imagine how the centrifuge works :

Imagine the unit which is a centrifuge oil filter ( on big marine diesel engine 20 cylinder MTU, 5,766HP at 26,000 lbs dry weight ) , imagine it is our MB centrifuge,
hence the engine oil is the vapor/gas ( light weight ) and the dirt is the oil ( heavier ).


The one on M278/M157 LEFT bank is a simple oil-vapor separator and so is a non centrifugal powered Catch Can equivalent.



....


.....



Now, one may think that Catch Can works well because it can be plenty of water in there.
It is only a simple dew point temperature effect.

Our exhaust gas is full of water vapor, that is given, from the process of combustion.
Water Vapour
Gasoline engine exhaust gas contains a weight average value of 10 % water ratio.
The main sources are hydrogen atoms as part of the hydrocarbons of the fuel and, in negligible amount, air moisture of aspired combustion air.
3 Oct 2017
https://www.jstor.org/stable/2642253...mbustion%20air.

So whatever the piston blow-by ( crankcase air ) produces, that gas has lots of water vapor.
Due to the compression ratio being easy 10 to 1 inside the combustion chamber, basically we get 100% humidity in there.
So the piston-blow by is a "wet" dirty air/gas. When the hot/warm piston blow by aka crankcase air touches a colder surface of an ALU Catch Can, the water vapor will
turn to liquid water. One only need less than 1 Celsius difference to get liquid water out of wet air with 100% humidity, we call that condensation.

Use this calculator , Dew Point Calculator, that tells you at what humidity %, we can get liquid water out of water vapor ( gas ) by simply reducing the temperature.
https://www.calculator.net/dew-point...us&x=Calculate

This is the reason short driving is bad for the engine, as the water vapor will turn to water at engine OFF and into the engine oil and engine oil not hot enough to get rid/evaporate the "water".

If you have winter in your place, if the caught water in the catch can freeze, you will do more harm than good for your engine PCV system.
That means you blocked the low/partial load PCV system.

I give you a comforting data :
When engine is at idle after a drive, at say 600 RPM, typical intake manifold pressure is 0.35 atmosphere.
with a working PCV system, that means the crankcase will experience the same lower than atmospheric pressure.
This means there is only 35% of air volume compared to 1 atmosphere of your location...assuming at sea level.
So you need not too worry of how much "wet" air inside the crankcase.

My advice is, maintain your PCV system at its peak performance at all the time, rather than using Catch Can.

So when you get say lots of oil in the Catch Can, that simply means your PCV centrifuge and whatever check valves they use needs some love and care...they are worn out.

M278/M157 intake manifold can not be as oil free as M276.820 3.0 Turbo.
These 2 engines and M276 3.5NA lack the more brilliant design of the 2nd fine oil vapor separator of M276.820 3.0 Turbo , the long rectangular unit.



It is inevitable that intake manifold will have some oil trace from oil mist.
The better the PCV system is in terms of gas flow, those fine oil mist which its PCV system can not separate out will end up inside the intake manifold, that is given.

The key is to set up a baseline, replace PCV system when it is still decent and not when it has worn out.
I am only at 40,000KM now, albeit 10 years old and I am going to replace my PCV system , all of it.
This is because i don't like any such device to perform less than its new state of being.

M278/M157 is a pain in the azz to remove its intake manifold to actually see oil traces, but it is what it is with such power it can make.
We loose some, we win some.

I shown the dimension of the NEW seal at the centrifuge end cap seal ID at 19.60mm, vs the spinning Oil Drip Pan OD at 23.99 mm.
By my simple calculation, if the centrifuge end cap seal ID already at 21.5mm, replace it. The near 4.5mm difference of a new set creates the sealing surface.
That seal inner diameter is very flexible and thin, as to create a nice sealing surface.

23.99 less 21.5mm = rounded as 2.5mm.
So the sealing surface only left 1.25mm all around and that is as low as I would go.
When I remove/replace my old centrifuge end cap and the Oil Drip Pan , I will measure them and come back to this thread.
I will do it this year, but not so soon.

S-Prihadi

BTW, one can send a boroscope into Port 1 and see oil traces inside the manifold, at close to Port 3...yes ?

Ultrakla$$ic

so Mr S-Prihadi, are these the components I would need to rebuild my PCV system on my m278 biturbo engine or is there more?? Thank you so much for your valuable input.

S-Prihadi

Ultra,

Your chassis is S class W221.
You need to use EPC and get your car VIN number in the parts search, as I am seeing some hoses with check valve is different from E class.

Assuming I use the correct chassis code, these are what I would recommend to replace but please verify it with your VIN.

Item 5 and item 20



If item 40 does have some sort of check valve, you should replace it.



=================

Is this how your brake vacuum hose looks like ? It has the P/N printed on it , you can verify

Supposedly it look like this :
https://www.ebay.com/itm/285286617822





==============

The fuel vent hose into port no 2, I am confused if for a W221 chassis. I do not know which one it should be.




.





..........

Also, does your engine have this hose ? Item 100 and 70



Visual of item 100 and 70

Genuine Mercedes Crankcase Breather Pipe Plug | 0099972972
https://www.autohausaz.com/pn/MB-0099972972

Genuine Mercedes Crankcase Breather Pipe | 2782031217
https://www.autohausaz.com/pn/MB-2782031217



==============

You should test your PCV system pressure ( negative, vacuum ), read here :
https://mbworld.org/forums/e-class-w...sure-test.html

The instrument is this type :
.


The test equipment is not expensive.


=====

This is MB official dealer and the prices seems good.
https://www.mbpartsexpress.com/



Have fun checking your PCV system.

Ultrakla$$ic

Yes Mr Prihadi, I have a 2012 s550 w221 m278 beauty! I am EXTREMELY indebted to you for your kindness and very comprehensive reply! My car does have all those hoses and lines as you've outlined, the only problem is either the Germans have hands smaller than a mouse or they didn't want us tinkering with their masterpiece.!!!!!! Trying to get to ANY part on this behemoth is going to take disassembly of practically the whole car. Guess I can start ordering parts and get ready to approach the back of the engine from underneath the car. Thank you sooooo much for your reply!

Looks like FCP Euro already knew us poor saps would need something like this since they've put together a KIT already.... LINK

S-Prihadi

You are most welcome.....

Wow, FCP Euro does know.
As far as PCV system, yes those are part of it and a nightmare to replace for some.

The hoses with check valves I mentioned are to make sure you do not loose your turbo boost from a weak check valve.

Here is a good video of OIL and VAPOR separator, and it is not a catch can.
Observe how it is running warm coolant to its body to warm it up, as to not get condensation.
this is also a centrifugal unit but passive one and not powered by camshaft or electric motor



No, you do not need to get this.

go team

You do not need a catch can. What you need is something that will prevent carbon soot from recirculating to the intake tract. There is already a system made specifically for that.

https://vm.tiktok.com/ZMMxgMu9o/

The above is not a catch can. It is an inline trap for soot. You do not need a condensator (catch can) as the centrifuge has eliminated droplets already but is not capable of eliminating soot (brown in the post above). Its easier to wipe the cannister than chase soot in the intake, manifold, and if left long enough, carbon build up on valves. In the post, the return path (top port) is so much cleaner than the bottom!

Ultrakla$$ic

Ok so today I lifted the car in the air with all 4 wheels off the ground and attacked taking the PCV off from underneath the car, fishing my arm along side the exhaust and was able to remove and inspect my PCV and oil drip pan. It looked brand new without a single hint of wear on gaskets and oil pan metal shaft. I bought my car from an 80 year old man with an impeccable maintenance history so evidently either the maintenance schedule he kept with frequent oil changes and/or it's been changed in the recent past. Either way I'm golden!!

S-Prihadi

Wow, your hands must be long.
Me a RHD car, steering link is there under the car, still, I am sure my hand can not reach PCV system from under the car.
Good one my man.

jcarsnz

Tasos has posted a video where he discusses the PCV system on the M157/278, and where you might install a catch can, quite an interesting watch.

https://tinyurl.com/4h6vxweu

I had my nose behind the right bank in the weekend while replacing plugs/coils.. I removed the firewall to get better access to cylinder #4.. but can't see how it's possible to replace the Vent Valve, it's way too tight of a space to be wrenching in that region (W166 ML63).

Ultrakla$$ic

double post

Ultrakla$$ic

Yes, if you listen to the video he mentions a "friend" had been asking him to do a video on a catch can setup for the m157/m278 engine at around the 18:25 mark............guess who that friend was that was asking???? This guy

kevm14

I think the simple explanation is the M276 turbo is the newest of this engine family, having a couple years of additional development time after the initial release in 2011 of the M276 N/A, M278 and M157.

kevm14

So I was inspired by this post. I bought the breather pipe P/N 212-430-05-29-64. It was $32. Takes 1 minute to install. I tried to test it with my mouth but this didn't really reveal any major differences between old and new. However, I did a ton of poking around Xentry while driving around yesterday (after installing this pipe). What I observed was very nice drivability even when my oil is hot (see oil pump solenoid thread for musings on thinner oil causing cam timing to wander around). So I am thinking my jerky issues could have been caused by boost control variation rather than cam timing variation. Maybe one or both of these check valves (depicted as A and B above) was getting tired. I do think I should also do a centrifuge cover (which seems more invasive of a job than it was on my W221 with M273) at some point. Also need to drive it more to make sure the issue doesn't come back but so far so good!

I already renewed my vacuum pump main check valve though the one in the car seemed perfectly fine.

For the evap pipe with check valve (port 2), I would think if boost was getting through that, it would set evap codes, no?

S-Prihadi

I do not have experience with US cars more advance EVAP system.
Mine is a simplified version EVAP, no pressure sensor of any kind, not even at the charcoal cannister.

Only a solenoid valve to open the fuel vapor line towards engine intake.
I can see the purging command via OBD2, no problem. However mine will never be able to detect any leak.

In theory if the port 2 check valve failed on your M157, I am sure the EVAP sensor system would be able to see high pressure from boosted condition.

Your car thru Xentry can it run EVAP leak test ?

.....

On the subject of : So I am thinking my jerky issues could have been caused by boost control variation rather than cam timing variation.
It could be . Must test check valve using pressure pump gun up to the maximum boost your engine is capable of.
I have a very slow leak on my duo-check valve, the one below :



.




This is how slow the leak is. I pushed air against the check valve simulating a 13 psi turbo boost. My boost is only 12 psi max.


But since my intake manifold does not share vacuum hose belonging to a vacuum pump heading to a brake booster like in M278/M157 , my boost will be lost to the engine crankcase.

The check valves on our vacuum pump is of no use ( air-flow direction wise ) against positive pressure from outside of the pump, like boost pressure intrusion let say in M278/m157 case.

---

Come to think of this discussion with you, you can actually monitor boost intrusion into your vacuum pump system.
I installed a vacuum pump pressure monitoring, using a vacuum sensor, it is a PSI-A sensor not a negative reading sensor. Banks Gauge does not sell vacuum sensor, only PSI-Absolute sensor.
I can read vacuum, it is just not shown as minus sign. So when I read ambient pressure at 14.7 psi assume sea level, that meant my vacuum system has zero vacuum.
If my gauge reads near zero, that means I have at least -14.5 PSI, a good vacuum.

If in M278/M157 application using the same set up, you can troubleshoot boost intrusion from the reading at WOT 1st and 2nd gear pull, you should never see higher than 0.2 PSI on the gauge.
Of course you can't use the brake booster for this test as it will eat up the vacuum. Idle a bit to build up maximum vacuum from vacuum pump and then redline 1st and 2nd gear.

This is how the vacuum sensor works for my application :

kevm14

Did another commute, and the ride home was pretty hot. Hot for me is low 90s on the cluster. I definitely think this vacuum pipe fixed the low RPM surging issue that I thought was cam adjusters. Pretty interesting. I would suggest that the $32 vacuum pipe did more to improve drivability than doing all 8 plugs and coils, which should raise some eyebrows around here. Even hot the throttle has a pretty solid and direct feel to it, which was lacking before. There is still an MCT jerk, but it's only sometimes and only once. This is just the nature of the beast. The issue before was a continuous jerking/surging while accelerating and shockingly that seems to be gone now.

I need to do the breather cover since I know that apparatus has a check valve as well. I think I will skip the evap hose because I know the car will be sensitive to any evap malfunctions or pressure fluctuations. Is there anything else that I should be looking at? This was a good lead!

S-Prihadi

Well, the logic is, the longevity of the few check valves in use would be similar...I suppose.
The boost pressure is equal all over the port A and B at the intake manifold.

But what may be helping the fuel vapor EVAP system check valve unit,is the use of the electric purge solenoid which is a shut off valve when not powered.
So for boost intrusion to go to EVAP system it need first to damage the simple check valve and then the electric purge solenoid.....BUT......

BUT...., if M157 MED 17.7 ECM uses the same algorithm for fuel vapor injection like my M276.8 MED 17.7, a bad check valve will cause boost lost into EVAP system.

Here is how the ECM commands the fuel vapor into engine. It does not care when and if the engine is actually under boost condition. It simply relies on the check valve.



...




See, even while intake manifold is at 8 psi above ambient pressure aka boosted, the fuel vapor valve is still being opened at 100% duty cycle full blast open.



Let's find a higher boost part of the log.



....



Wow, them engineers totally do not care about the presence of boost. Its like they treat the engine being a normally aspirated. Higher engine load...inject more fuel vapor



.


This is the hose for fuel vapor you speak of ?
https://www.ebay.com/itm/174625574224




This the purge valve on your engine
https://www.ebay.com/itm/363428789926



I replaced my purge valve already, not because it is leaking, I hate the extra noise it made as it is aging at 30,00KM ish. I am hyper sensitive to changes in my engine noise.




....

My engine oil vapor & fuel vapor into intake manifold below. You need to map out your engine's like I did to see where else there is possibility of a boost leaking out into those
oil vapor and fuel vapor injection into intake manifold. Mine got a dummy EVAP pressure sensor when I audited the wiring diagram vs actual hardware

https://mbworld.org/forums/e-class-w...re-sensor.html



Mercedes EPC is too segmented, as such I can't figure out which hoses goes to where exactly until I see the real hoses on my engine.

....


I think this is how M157 / M278 fuel vapor flow is , start to finish.....if so, it is a bit less complicated than M276.8 3.0 Turbo.




....





See your Xentry M157 under EVAP section, what DTC database it has ?
Since US version get that #720 sensor, perhaps verify if OVER Pressure will trigger the sensor or not ?
If emission concern is a leaking fuel vapor into atmosphere, pressure loss is then what they need to know and not over pressure. I am assuming here.

.Perhaps use a hand pump to generate 1 - 2 psi into fuel EVAP system, see what DTC will pop out ?
My EVAP is a dumb version sensor-less, so it will not report anything.

kevm14

So I'll give you boost COULD be getting lost if there is a vented state AND the check valve doesn't hold. But as you said, in a purging state, it will happily purge during boost, relying on the check valve. So, if there was a problem with my check valve, I would be pressurizing the canister (and fuel tank???) with intake manifold boost. If this happened regularly enough to actually cause boost loss, I am pretty certain the various evap diagnostics would be unhappy with tank pressure and set a code.

I could simply monitor tank pressure while driving around. There should be a PID for that.