[rocketjon]

On this site I saw that someone recommended simply periodically sucking coolant from the reservoir and refilling it with fresh coolant that was the same as in the system. I have a 2015 that has the original blue coolant,which I assume is the Mercedes 325, and that's what I would add. I would be willing to do this reservoir drain and fill after almost every time I drove it over at least several miles until I went through about a gallon of 50/50 mix. Then, maybe at about 6 month intervals, I would do a reservoir drain and fill with the hope of keeping the coolant from deteriorating. The reason for this unusual approach is to avoid the hastle of disconnecting hoses in hard to reach places and run the risk of damage due to air in the system. The car has 12,000 miles on it and I will continue to drive less than 1500 miles a year.
I would appreciate any comments on whether you think this will keep the coolant in good condition. I searched for the post where I first saw this mentioned but I couldn't find it - maybe someone knows. I am also considering getting the Airlift 550000 system to get rid of the air bubble concern.

 

[gtdump]

It's not hard to drain and fill, nor does it take a long time. It is unpleasant pulling the hoses if you don't have a pair of hose clamp pliers that fit and a hose hook, but those tools are not expensive.

I don't think it would be an effective method of flushing as you're mixing in the new and old and will reach a point of diminishing returns quickly. Some quick calculation suggest that to get the coolant to 99% new and 1% old coolant would take...... 60 changes using 30 liters of coolant to get there....based on a capacity of 4.7 liters and changing about 0.5 liter at a time.

I would think those 30 liters of coolant would cost more than taking it to the shop and having them do it and certainly more than buying a set of hose clamp pliers and a hose hook. Given there's still the frustrating part of doing it, which having done it I completely understand why someone would pay a shop to do it for them.
Bleeding the air out of the head is actually pretty easy, there's a hose you disconnect up top just behind the throttle body, leave it open until the coolant comes out and reconnect when it flows, then keep the coolant topped off.

Edit: fixed some bad math

 

[rocketjon]

It's not hard to drain and fill, nor does it take a long time. It is unpleasant pulling the hoses if you don't have a pair of hose clamp pliers that fit and a hose hook, but those tools are not expensive.

I don't think it would be an effective method of flushing as you're mixing in the new and old and will reach a point of diminishing returns quickly. Some quick calculation suggest that to get the coolant to 99% new and 1% old coolant would take...... 60 changes using 30 liters of coolant to get there....based on a capacity of 4.7 liters and changing about 0.5 liter at a time.

I would think those 30 liters of coolant would cost more than taking it to the shop and having them do it and certainly more than buying a set of hose clamp pliers and a hose hook. Given there's still the frustrating part of doing it, which having done it I completely understand why someone would pay a shop to do it for them.
Bleeding the air out of the head is actually pretty easy, there's a hose you disconnect up top just behind the throttle body, leave it open until the coolant comes out and reconnect when it flows, then keep the coolant topped off.

Edit: fixed some bad math

Thanks for the suggestions. I have the pliers, maybe not quite the right size, but I am embarrassed to say that I have never heard of a hose hook, but now will buy a set. Your math is impressive but I'm not sure it's fair to shoot for 99% since the average concentration over four years without adding fresh coolant would be a lot lower than that, I think.
I still will likely do a drain and fill as I did one about twelve years ago on my first smart. However, I turned 80 two days ago and grabbing onto that hose with arthritic hands seems a little harder than it used to, but the tools will definitely help. Thanks again for your detailed reply, maybe some others learned something new also.