S-Prihadi

Gents,

1st part is here : https://mbworld.org/forums/e-class-w...2-2-hoses.html


I have installed a K thermocouple labeled 2B on the log file, at the EVAP out, the big low pressure pipe, suction pipe.





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Now that K thermocouple is activated to my Banks Gauge, I can share some data.





Here is a 105 minutes log at 5Hz. First 36 minutes is at the garage, stationary. Minute 37 to 105 is on the road.
Where you see EVAP temperature ( Thermocouple 2B ) rise above 6 Celsius and all the way to 20ish Celsius, that is me shutting down the AC, I was smoking.



Zoomed to see the temperature better



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This is a short run log of 19.4 minutes only , car got on the road within minutes of engine start.


Zoomed, to see temperature details better



.
EVAP OUT pipe skin temperature vs car velocity




Engine coolant temperature vs pressure of coolant from rear azz of Bank 2 to a now GONE heater core.




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Ever since the heater core bypass, the coolant having no more to fight restriction at heater core, its pressure has dropped a lot at WOT 6,000 ish RPM.
NOTE : In the entire cooling system, the coolant pressure IS NOT the same. I will explain more later.

The 105 minutes log coolant pressure towards the now GONE heater core.





Below is an old log, where the heater core was still not bypassed. 124 minutes, also at 5Hz.




Notice the coolant pressure difference at 6,000ish RPM. Was approx 22 psi with heater core and now maximum only approx 13 psi without heater core.




WILL CONTINUE................

S-Prihadi

This is the flow diagram...





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I meant bypass is simply heater core not included in my cooling system anymore. I did not PLUG OFF the coolant flow from Bank 2 rear azz back to mechanical coolant
circulation pump at engine.





I am curious for M276.9 3.5 NA
Since it has no turbos meaning engine block hot coolant return is only via heater core and radiator only.
What if someone got dumb and closed off the Bank 2 rear azz coolant flow because his heater core is leaking, what will happen to the cooling system when and if
the thermostat has not open up yet to divert the flow to the radiator ?


Looking at the pressure increase due to heater core restriction, no wonder heater core can leak ahead of the radiator.
Radiator never get too see that high pressure of 22 ish PSI, I do not think so. It will be slightly less than that.
I can't measure pressure input from a fully open thermostat to the radiator input. I do not have that king kong size sensor-hose adapter.

You guys must be wondering, what is the pressure at the coolant reservoir bottle ?
It has a 1.4 BAR or 20.3 PSI maximum safety burst pressure by the cap.
I once installed a sensor right at the big hose of coolant reservoir bottle, it is much a lower pressure.
Never exceeded like 8 PSI at 6,000+ RPM as I recall at 100 Celsius of Engine Coolant Temp sensor. I have to find my old log file.
The reason the coolant reservoir bottle is at lower pressure is because it is so close to the suction port of the mechanical coolant pump on the engine, which is a a very low pressure zone.
Also the mixture of cooled coolant from radiator output with even a hot coolant from Bank 2 rear azz, still made the coolant at that zone not as hot as the one at thermostat output to radiator input.



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One will ask, why would I log my EVAP OUT pipe skin temperature ?
This temperature data correlate to Saturation Pressure of the R134A refrigerant in use.




That means I have a live data log of what is going on with my AC compressor.
By next year, if not end of this year, I will install 2 more K thermocouple sensors.
One is at compressor output to condenser to track compressor temperature.
One more is at the condenser output to the IHX, internal heat exchanger which is the special pipe type heat exchanger, the mini one.
By then I can detect any negative trend which can effect the longevity of my AC system.

Per 2 years max, I always verify the R134A fill rate. 8 grams lost per year from the compressor seal is expected.
I will also verify the oil color and its acidity ( test kit available ), using special sight glass.
If I loose enough R134a from a leak, I will damage my AC compressor, because low refrigerant level will make compressor oil get stuck at EVAP and the AC compressor
will then have black death from lack of lubricant.

My number 1 fear is having to replace EVAP and having to tear down entire car dashboard...NO NO NO, no way. The dashboard tear down is what I do not want.

At my low mileage per year, by year 2034 my car would at best only do 100,000KM. Now at 40,000 KM.
That is only 100,000 / 21KM-H or 4,762 hours. Any proper maintained AC compressor which does not over heat, can exceed 8,000 hours easy.
So up to 2034, all I need to do is replace all the hoses and o-rings at EVAP and at hose ends.
By 2026 or year 12th, I will replace 3 hoses and the filter drier, which I already bought since last year. This 3 hoses are the one at hot zone.
By year 14th to 16th or 2028 - 2030, I will replace the main hose-pipe where the IHX is at and is towards the EVAP, and this is the cooler zone one, hence it should last longer.

These hoses are rubber, so it may look good from outside, but it can crumble slowly at the inside and bye bye compressor, chewing the rubber dust or particles.
Our W212 EVAP and Condenser is super small micro channel type. Cleaning them is not an option, throw away is the option.
That is why I rather be super attentive now and not suffer later on when my car gets older.

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The performance of the AC is so very good now and I can't be happier, with the heater core now being no more giving its thermal power inside my cabin/dashboard.
The heater core naked pipe ( no insulation at all ) alone is already a bad heat intrusion, let alone the heater core radiator itself which is so big.
No matter how MB insulates the heater core from the EVAP cold side , which is poor insulation anyway so thin and close proximity..... 95+ celcius metal with a foot print so big, it is basically a sauna maker.

MB could have spent extra US$100 at the most and our M276.xx engine can have heater coolant divert valve like M271.8 on a W212 E200/E250 or C250 W204 and AC will be cooler.
So now W212 E200, E250 vs E350 M276 in the tropics, the E350 / E400 is a big time looser in AC system cooling power.


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