Excessive contemplation over a W205/M274 coolant replacement

[BEERMAN]

I have recently finished the annual service on my 2017 W205 without any issues, as is customary.
I typically assess the quality of the brake fluid using a tester and replace it according to its condition.
I perform the same procedure with the coolant, verifying the DC voltage to ground, and if it is below 0.4V, we are satisfactory. For the past three years, the voltage has been 0.15V; however, this year it has increased to 0.45V. Therefore, I conclude that it is no longer inhibiting galvanic corrosion and requires replacement.

No issue, I have replaced coolant numerous times, but not in this vehicle.

[BEERMAN]

The DC check method is depicted here:

[BEERMAN]

 

[BEERMAN]

Enquiries on the forum indicate that the coolant is designed to last for 15 years. I am pleased to make the modification promptly, and it appears that the coolant specification is MB325.6 (concentration) or MB326.6 (ready mix) based on this information: Coolant Ambiguity | Engine

I need to locate the MB32*.6 specification. Impressive. I am capable of accomplishing that.


Firstly, what is the required amount? My automobile is distinctive due to its manual gearbox; hence, it likely lacks a gearbox heat exchanger in the radiator, unlike other Mercedes I have owned. The owner's handbook is entirely unhelpful, merely directing me to MB tech sheet 310.1, which is intriguing but lacks volume information.
Mercedes-Benz Operational Fluids This coolant appears to be costly, so I prefer not to purchase an excess.

Secondly, it appears I must employ a vacuum bleeding technique.

[BEERMAN]

 

[BEERMAN]

I have never performed this task before. Is it truly necessary? Presumably, the expansion tank remains the highest point in the system. The standard procedure involves activating the heater, draining fluid from the lower hose or designated drain point, and replenishing the system. Is it essential to utilise STAR to operate the water pump for bleeding? Surely, running the engine as I have traditionally done will suffice. Has anyone executed this procedure on an M274 C-class? I feel as though I am overanalysing the situation and should proceed. I do not intend to conduct a complete flush since the system has never been opened, and I am still "six years early." My primary objective is to replenish the corrosion inhibitors within the system. Even if I remove 5 litres and replace it with 5 litres, this must be preferable to allowing the system to remain filled with degraded fluid. Any insights and advice would be greatly appreciated.

[BEERMAN]

Certainly, a brief follow-up regarding this matter. The coolant is relatively new, hence I will perform a partial replacement every few years.
I purchased two cans of authentic MB325.6 from Eurocommercials MB on eBay for £35 each.
I purchased this hoover bleed kit from eBay for £22.


I briefly operated the vehicle to adjust the heater to the "Hi" setting for "hot".
I elevated the vehicle from the primary jacking point beneath the front and positioned it on improvised ramps constructed from repurposed countertop portions, achieving a 70mm lift.
It is necessary to detach the front undertray to access the radiator bleed tap. To remove this, the engine undertray must be detached.
Detach the filler cap from the expansion tank.
A spigot for a 6mm bore hose is located at the base of the radiator to facilitate coolant drainage into a container. The tap is, as anticipated, difficult to operate. A minor difficulty with the cranked nose pliers assisted, although the ears on the tap began to deform. It secured adequately after emptying; however, next time I would detach the lower radiator hose. Approximately 3 litres have been drained. Insufficient quantity.
Here is additional information regarding the vacuum bleeder. The quality is satisfactory; however, the airline fitting resembles a nipple compatible with either an American or an Asian automotive pattern airline, to the best of my knowledge. A standard UK quick coupling cannot be accommodated.
The fitting is not compatible with UK standard threads when unscrewed for replacement. Rather than the standard 1/4" BSP thread for aviation applications, it was M14x1.5. Rodents. Altering the fitment is not permissible.
I machined a fitting to connect an airline to the M14 fitting. I fabricated a hose tail profile on a section of hexagonal bar, which I threaded M14-fine at one end, and connected it to a whip hose. I now possessed the vacuum bleeder, equipped with a whip hose, which I could attach to my compressor.

To utilise it, insert the assembly into the neck of your expansion tank. Connect the airline and circulate air. It extracts air from the system, causing all the hoses to collapse.
Subsequently, seal the valve on the fitting of the assembly located in your expansion tank, and allow it to remain undisturbed for several minutes to ensure the vacuum is sustained.
Detach the 'vacuum' manifold from the assembly equipped with the gauge (all fast couplings in the package have the same design). The specific pattern of these is unknown, however it is irrelevant, as they all interbreed with one another.
Insert the suction line from the kit into the quick coupling, ensuring the opposite end is placed in your coolant reservoir.
Activate the valve on the assembly located within the expansion tank, and it will draw in the coolant. 3 litres out, 3 litres in.
And you have completed everything!
Essentially, you are undertaking the following:

It was relatively simple, and I would not hesitate to undertake it again.
However, let us examine the expense:
£35 for coolant
£23 for the vacuum bleeder and approximately £7 for the whip hose.
£20 for the M14x1.5 tapping tool
One hour dedicated to creating a fitting.
The total amounts to £85 for the equipment, in addition to some time spent organising all the items.
Would your dealer impose this fee for a partial change?
I possess the kit for future use, hence only the coolant expense remains moving forward.
I did not drain a significant amount, nor did I drain the block; nonetheless, performing this procedure biennially with coolant designed for a 15-year lifespan will ensure it remains partially refreshed and effectively mitigate corrosion.

* Due to the absence of a tap on my compressor outlet, I further incurred an expense of approximately £30 to create an inline "tap" for connection to my airline. I purchased a 1/4" BSP inline tap and installed a male and female PCL fitting on either side of the valve. I installed this in the circuit between the outlet hose of my compressor and my new whip-line manifold. This approach would allow me to assess my situation and proceed with caution. I did not wish to attach the hoover bleeder and rapidly discharge the complete contents of my air receiver at once. I desired a valve to regulate the flow. It functioned effectively.

Revision for the initial post.
I mistakenly inverted my calculations; it should be above 0.4V for protection.

[TDudette]

A 2017 W205 is expected to utilise SI-OAT coolant (326.X), which has a four-year replacement interval for many Mercedes-Benz vehicles. It is typically pink or red.

The 15-year coolant is 325.X and is typically blue-green.

[BEERMAN]

Thank you for the valuable information. Thus, there is an increased impetus for consistent modifications!

[CyberNinja]

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