S-Prihadi

Gents,

I was doing the vacuum pump system integrity here : https://mbworld.org/forums/e-class-w...rity-test.html
and Cali was discussing about crankcase pressure which can effect vacuum pump performance....which is true.
Our vacuum pump need to dump air from its internal and it dump it to the crankcase, so if engine crankcase pressure is high due to PCV issue and whatnot,
the vacuum pump may get its performance reduced.

I can't find any WIS information of what is to be the crankcase pressure ( negative pressure mind you ) value when system is healthy.
I got BMW one..... https://static.nhtsa.gov/odi/tsbs/20...45282-9999.pdf





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I was thinking hard where do I get a high precision up to +- 100 millibar vacuum/pressure gauge ?
To put in context how low value this is :



This is HVAC ducting works tools, or for gas service, gas as in vapor/GAS LPG and not gasoline.

I then remembered...DAMN, I have such a tool for calibration/measurement of my dive regulator 2nd stage cracking pressure.
I got this one from Scubapro, which is actually made by AZ Instruments Taiwan :
https://www.newegg.com/az-82062-test...2YK-01Z6-00WS4

It can do 6 PSI vacuum and pressure


The rigging



My very thick blue silicone hose thankfully has the OD suitable-matching to the oil dipstick ID. So I can use it ....yipee !!!!!



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Here is the test summary, need to be in video form as I need to synch the two data sources and I want to see live changes.




This is a good video example of a normally healthy N55 BMW engine at -1.454 InHg ( 49.2 Millibar ) and also a N55 with too high vacuum exceeding 4 InHg vacuum or -4 InHg.( above 135 millibar )

Inch Hg conversion to Millibar



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My M276.820 3.0TT PCV system is as described below : https://automotivetechinfo.com/wp-co...and-Tricks.pdf

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I wish MB in WIS/EPC has crankcase pressure data for us
I tried for an hour, I can't find any.


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The importance of PCV is not emission only. It takes away dirty blow-by gas from NOT ruining engine oil too.

Let Wiki explain blow by, so me no need to type much :
Blow-by, as it is often called, is the result of combustion material from the combustion chamber "blowing" past the piston rings and into the crankcase. These blow-by gases, if not ventilated, inevitably condense and combine with the oil vapor present in the crankcase, forming oil sludge or causing the oil to become diluted with unburned fuel. Excessive crankcase pressure can furthermore lead to engine oil leaks past the crankshaft seals and other engine seals and gaskets. Therefore, it becomes imperative that a crankcase ventilation system be used.


My dive compressor blow-by is water vapor due to 1:7 compression at all its 3 stages, all the way to 3,260 PSI / 225 BAR.
This ruined the expensive compressor oil FAST, 200 hours maximum use, while the dumb-azz manufacturer reccommended 2,000 hours ...LOL
Note : My dive compressor lubricating oil can not go hotter than 60C /140F, so no way the water in oil can evaporate from heat.

200 hours of use, oil is still okey, but look at the water in oil at the last 0.8 liters drained oil. Total capacity is 2.8 liters.





RIGHT TO LEFT is the drain sequence : 1 liter , 1 liter and then 0.8 liter.
See the unpleasant surpise at the bottom of the pyrex.




If new, the oil color & clarity is below




END

CaliBenzDriver

This is another very interesting topic because every engine has one of these PCV systems and they come with many different incarnation... meaning there is no consensus on how to make a good engine breather. BMW sure found a good way to make an expensive unit and MB a labor intensive contraption under high pressure fuel pumps. ​​​​​


Thank you for looking into PCV because this system is tied to ECU/TCU performance through MAP.
It help the car drive poorly from multiple symptoms: heavy accelerator, off tranny shifts, poor brakes.

As we could expect, there is a difference between turbo and NA to make up for intake boost pressure. Turbo has an additional filtration perhaps more effective than NA engine at stopping oil migration onto intake valves.


MS live pressure study 🙏

The normal target crankcase pressure is slightly negative -0.5Psi.
It can fail with either too much vacuum or too much pressure for different reasons as well as both failures combined with high blowby and busted PCV check-valve.


This system requires maintenance parts around the 75kMi mark along with HPFP rollers to preserve camshaft lobes.
The built-in check-valve membrane fails and pulls controlled vacuum. Plastic conduit gets obstructed with deposits. The fix is complete PCV kit.


Diagnosis:
How to simply identify PCV issues... not exactly simple because it depends on engine TT/NA and engine blowby condition.


Dead give aways are:
-- extreme vacuum: video shows hissing condition from extreme vacuum at oil cap!
-- extreme pressure: engine leaking its oil from every seals and pressure found at the cap instead of minor vacuum.


Fixing the blowby starts with good oiling of piston rings with a quality oil based on hot/cold temps - Suggested Motul 10W50 grade better than Mobile1 10w40.

++++ Burned Oil temp vs Tstat.

Fancy poor cooling
Your awesome design document has this other contraption described right next to PCV system.
There is a relationship between overheated vaporized oil and cooling control.

The engine uses both a mechanical plus an electrical pump, an ECU controlled Thermostat a supersonic PWM fan on a 20psi low pressure system.

Based on what we know the Tstat is likely used as failure point to cause heat damage from marginal cooling.

We know Tasos always find Tstat in two pieces in failed engines he rebuilds. He even created a special bypass unit he sales.

Theoretically this MB temperature regulation should be able to cool well with a large radiator. That's not what I personally witness - I believe the management of the smart Tstat opening is affected by poor control just like "Voltage Yoyo" or the "Pump Solenoid".

> Something along the line of :
--- skewed temperature sensor that makes poor regulation ??

--- Poor Tstat heater PWM/Mechanical control is not working well to impact linear control ??

--- Firmware learned map regulation of coolant Temps is wicked like the yoyo ??

In theory cooling design is above and beyond, in practice it is the opposite: PITA! This may deserve debugging attention to brainstom improvement.

My radiator fan running in winter without HVAC says something about engine heat being hard to control. (FYI: it has positively improved with normal oil pressure). I guess a Temp sensor says coolant is too hot... where tstat does not open enough... of course no code - With limited oil engine was noticeably much hotter, now engine is cooler but coolant is the same... cooked Tstat got seized???

I am due to clean my firewall hidden ECU GND, perhaps this will be another positive transformation for Tstat control