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Letting a freshly flushed cooling system bleed by idling the engine isn't going to do it, no matter how careful one is. The pump needs to MOVE coolant to push all the air out, and that means RPMs. You burped the system by driving; that's why the level went down. If a cooling system boiled water every time it ran, don't you think you'd constantly be replacing lost coolant?
No because the heat expansion/boiling takes some volume that raises the reservoir level and with the pressure valve keeps it at what it is. When overheated once it pretty much does take care of the level.
You can easily experiment with this. Just add coolant or just distilled water in the reservoir to fill it up from the level you have it. Just adding water is fine as the reservoir is not very big compare to the 10 liter coolant volume. You will find that the coolant level very quickly returns to LE level it was at in the reservoir.
In a normally operating (not overheating engine) the coolant does not boil thanks to the elevated boiling point of the liquid that is elevated even more by the pressure in the closed system. It really is that simple. If yours is boiling, something is wrong.
Vapor (boiled liquid) has essentially no cooling ability, and whatever section of your motor (exhaust valves?) started to boil the coolant would quickly corrode and pit, introducing metal into the cooling system and ultimately start wearing parts and wrecking pumps.
Somebody tell me why I'm wrong.
Edited to add: I suppose that if one was to do a full throttle run uphill for an extended period of time then shut the engine down immediately, yes. There could be an issue. But in general I stand by this post's original sentence.
Last edited by rapidoxidation; 07-31-2021 at 09:22 PM.
I agree, fluid is not or should not be boiling… maybe very localized areas. However, any drop in level after filling, in my opinion, is simply purging. Idling with heater full blast does a good job, but after a drive I always find the level a little lower. From there it remains steady.
In a normally operating (not overheating engine) the coolant does not boil thanks to the elevated boiling point of the liquid that is elevated even more by the pressure in the closed system. It really is that simple. If yours is boiling, something is wrong.
Vapor (boiled liquid) has essentially no cooling ability, and whatever section of your motor (exhaust valves?) started to boil the coolant would quickly corrode and pit, introducing metal into the cooling system and ultimately start wearing parts and wrecking pumps.
Somebody tell me why I'm wrong.
Edited to add: I suppose that if one was to do a full throttle run uphill for an extended period of time then shut the engine down immediately, yes. There could be an issue. But in general I stand by this post's original sentence.
The mentioned "hot spots" happen on heavily used engines, but evidently MB consider that not an issue in sedans.
So yes, when you drive in 120F on 15 miles steep grade and keep 80 mph, would you make fast pull over and immediately shut the engine down, that MIGHT be possible, but doubt many owners will ever face such situation.
That said, I frequent SF - LV route, and Baker grade has the above parameters most of the summer. My diesels still stay at 90C and even I don't pull over there, the hot spots not likely would ever occur.
Unless you have a US model, Canadian cars should have tunnel mode (if disabled, it can be activated via Vediamo though. PM me.). It's not a feature that can be coded on US cars, you have to replace the climate control unit. I swapped out my US climate control unit for a European version specifically so I could have REST mode. Tunnel mode was a bonus.
Even if you don't normally drive with the windows open, it's nice to be able close the windows/sunroof with a touch of a button after using the Summer opening feature.
US climate control unit European and US climate control units European climate control unit w/ REST mode
So - I live in Canada, so I have the same panel as Europe. The cars here just show a recirculation icon and don't commonly have a "MAX COOL" button labelled. I'm not sure why that's a thing in the US, here people just put on the recirc and everything knows that that cranks up the A/C...
Thanks to MB_FanAttic for pointing me to the appropriate place. It's actually very clear when you go to the coding in Xentry, it lists it out for you, this is code 009 and 010 and is shown in Vediamo as: KBUMLAKTIV (set to ja/yes) and KBUMLMODUS (set to Auto).
In Xentry there are a lot of user preferences under the HVAC module to set, for instance, whether you have a MAX COOL button, where you click AUTO if it turns it on or off or just turns Auto ON, whether the fan speed is shown when in Auto, and other settings. It's possible you can somehow get it to work messing with these options, but I have no evidence and it looks like MB_FanAttic's note to just swap the panel seems like it would work for everyone in the US. All I had to do was just toggle KBUMLAKTIV to ja and I was done, it works like a charm.
07-31-2021, 06:03 PM
