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Can you kindly verify if your engine's turbo coolant RETURN pipe (item 1) which then connects to a hose ( item 2), does the hose get connected to this unique Tee (item 3) ?
My car is Right Hand Drive
Close up of the Tee, item 3
Something is not right with such set up as found on my car, assuming your same engine as mine, does not have such set up.
Here is what is wrong with the set up on mine.
Why would send hot coolant from turbo's RETURN coolant line, to join/tee into a suction side of HVAC heater core circulation pump.
This set up only has coolant flow if I turn ON my HVAC temperature to MAXIMUM high and then the small Circulation Pump will run. I never use HVAC heater function, I am in the tropics.
So how does my turbo's liquid coolant can circulate under normal condition ? WATER PUMP SUCTION. I meant the belt driven cooling water pump.
What I call as turbo coolant RETURN pipe (item 1) in 1st photo, it is component 40 below.
Even the EPC is screwed up.
That item 3 Tee ( component 280 ) is shown connected differently than how it is actually on my car.
The hose item 2 on 1st photo is not in EPC page for my car.
I traced item 2 hose P/N and it is used on W207 E400 Blue Efficiency W207.361 and is the rare M276 3.5 TURBO M276.850, yep, such engine exist but super rare.
PS
If in any event, your HVAC blows hot air, hotter than ambient air if you are not operating the compressor, it could also mean that the small heater circulation pump is kinda "open" and allows hot coolant
to flow inside the HVAC heater core. I guess even if HVAC compressor is ON, if the leaky path at the heater circulation pump is big enough, we can loose cooling power a lot and one may misdiagnose HVAC as not cool enough or defective.
Last edited by S-Prihadi; Jul 25, 2022 at 05:42 AM.
Reason: add info
I know M276.820 from W212 E400 is a pariah engine, but I never expected the EPC and also 2020 WIS screw up is this bad.
My EPC is a 2018 version and my car is 2014, by 2015 is last year production for W212 E400.
3 to 5 years later in 2018 - 2020 and MB still can't get the EPC and WIS correct.... Damn !!!!
The circulation pump is used on nearly all MB vehicles during this era.
One vague WIS function description document has been posted on this site which outlines the circulation pump function.
The pump is generally used to boost coolant flow during low engine rpm, because the belt-driven pump is optimized for higher engine speeds and therefore has insufficient flow capability at low rpm. The reason for this is to improve fuel economy and emissions performance, because the belt-driven pump has a less aggressive impeller than it would otherwise have in a system without electric boost pump, and requires less energy at higher rpm.
And the boost pump has the additional function related to the REST residual heat function, if present on the car.
Please refer to WIS GF83.40-P-2020A Circulation pump, basic function, component M13/5.
Thanks for the information.
I think I realized I probably mis-visualized the HVAC system.
At First :
I simply do not believe MB on W212 keep pumping hot coolant into the hvac heater core without demand for heating.
90-100C skin temperature of the heater core even without air being blown across it is still heat radiation leaking into the HVAC housing assy
This such a waste of cooling energy the aircond compressor is providing. I been hunting down where is the hot water solenoid for M276 ( NONE !! ), unlike M278 with hot water solenoid/valve at rear of engine to cut of hot coolant flow to heater core.
So I am under the assumption that there is no flow/activation made by small circulation pump unless I switch temperature to HIGH.
On the other hand ....if above assumption is the case, how the hell my turbo return coolant will flow ?
Below speak of AFTER-RUN only and no in normal operation, which the afterrun is like turbo timer but coolant flow only and not engine + cooling fan like older cars.
I will do a test to see if under normal engine running , does the small circulation pump runs too even without HVAC temperature at HIGH (heat) ?
I am now beginning to believe that W212 with M276 could be pumping hot coolant at all times to heater core regardless we choose heat or not
If indeed this crazy HEAT-UP-MY-HVAC-HOUSING is true, I may install a hand operated water valve at the heater core input.
Wait a minute........ M278 is found in W212 as E500. The HVAC housing in the car is 100% the same as M276.
M278 has the coolant shut off valve to heater core.
That means M278 based W212 will have cooler HVAC because there is no hot heater core to spread heat.
How does one isolate thermal convection when the EVAP & Heater Core is so close together ?
Let say 25C is the ambien temp. Hot coolant at 85C, so a 60C delta.
Evap can only cool ( remove heat ) to say 3C air temp. so delta 22C only.
Heat is energy, cold is just the absence of heat. Making "cold" is waste of power.
Why design a system with heat "contaminaton" ???
I was always wondering why my W212 is not as cold as mid range Japanese cars in similar low speed blower setting which is 2 bar/stripe.
I have always blamed the pano roof which is also a true heat generating wide body bi-etch.
I could not find a W212 evap & heater core removal, only W211.
From post #5 above, it looks like WIS is showing stalled/old diagram...
old blower ballast module
So far what I've understood...:
M276 uses circ. pump to shut off heater coolant flow
M278 uses a valve like W211 to positively stop the flow in heater core.
Having a manual heater control valve sounds like a smart enhancement for tropical weather.
01. Chassis. Yep...make sense for the heater core keep getting coolant flow as humidity reducer. Some application requires dehumifier to work together with HVAC cooling.
Still I am curious to how many degree Celcius I lost from it. I think a fast pinch-the-hose for heater core input is easy to do for quick and dirty test.
02. Cali. I thought so too that circulation pump acts as a valve for heater core albeit at heater core output side, but my turbo's return coolant path is also blocked if circ-pump is not running.
Hence Chassis explanation makes sense that very much probably the circ-pump will run as often as needed for turbo's cooling....in other words heater core is then also getting coolant flow..hot hot hot my interior.
The evaporator acts as the air dryer during A/C operations. That how it gets loaded with condensed moisture!
When A/C stops, condensation runs down, temp soars and mildew develops with all the dirt trapped by circulating air.
I believe HVAC Module purposely uses the heater core to expedite drying the A/C evaporator AFTER car is stopped.
W212 has a humidity sensor located near the windshield rain sensor.
Cali,
Indonesian assembled cars if MB get usually the cheapo version of everything.
My hvac system is the basic one 580, it has no dewpoint sensor .
I think yours is 581 yes ?
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E400 Blue Efficiency W207.361 and is the rare M276 3.5 TURBO M276.850, yep, such engine exist but super rare.
