Hi. I am about to flush coolant in both a 2010 GLK 350 and a 2011 E350. First time.
Want to flush with distilled and use MB coolant etc. and do it right.

From what I am told, when you do it from petcock below, you do not get more than say 2/3 of the total coolant out .

So, if you then flush with the distilled water a couple of times and, at the last go-round, refill with the correct coolant mix (50/50), you have a blend of the original remnants and the new mix.
So how do you judge the mix? Is it even worth it? Should I just do a drain and refill?
I am confused. Help please!

 

Drain and fill.

 

Where did you read that you get only 2/3 of the coolant out by just draining it?

Almost all coolant is stored in the radiator and the large diameter hoses and the reservoir that all drain empty when you just drain the system from the little valve at the bottom corner of the radiator. Engine water cooling channels are very small and do not hold much volume at all.

Just drain it and fill it and then run it on idle with reservoir cap off filling it as air comes out from the system.

When you open the drain be careful not to break the valve stem. You first turn it 90 degrees CCW then pull it out about 1/4” and then you can turn it another 90 degrees to fully open the valve. You can also pull the stem out at this point if you like.

Some people have reported that this stem breaks easily and MB does not sell a new part for it. You need to buy a whole new radiator from them. Rescue for this is to go buy this valve stem from Chrysler/Dodge parts. They sell it as spare and is a perfect fit, at least for my 2010 E550 it is. Must be from the Daimler-Chrysler years…

 

It should be possible to get a new drain plug. Part number for my car is A0009970224.

 

That part number matches a radiator plug, but not the specific model. Does it fit your car?

it seems to only fit these below

 

According to EPC a few years ago this is the right one. I ordered it to replace the old plug if it had broken during flushing. But the old one is still intact. So, the new plug still waits to be used. At least it looks the same like the old one. 😁

 

I just remember other forum members saying Mercedes does not sell the drain plug but you need to replace the whole radiator to get it. This is for my 2010 model so perhaps there are plugs available for later years. I went to my local Dodge dealer and got the plug. I posted about this in this forum and had even a picture in it showing the original and the Chrysler plugs side-by-side for comparison. I installed the new Chrysler plug (valve stem) and kept the original as spare.

 

Both of those vehicles have 15 years coolants, so is it repair-related coolant change?
If you do it- replace chem pack, what on some vehicles is integrated into reservoir.