PeachParts Mercedes-Benz Forum - View Single Post - DIY: Mercedes C240 (W203) Radiator Coolant Flush w/ Pictures

bhatt · #4 04-18-2011, 04:06 PM

You are still leaving a bunch of coolant in the heater core by doing it this way.

I usually do the following:

1. Drain
2. Fill up system with water from garden hose to proper level
3. Run car until warmed up. Watch out as the car will overheat quickly with just water in it! Just heat up to normal operating temp
4. Let cool for a few mins, then drain again
5. Repeat steps 2-4 once more
6. Drain one final time, then refill with the specified amount of coolant. Once you have added the coolant, add water till full.

For example: system capacity is 10l but you can only really drain 8l (there is 2l in the heater core). This means you will drain the 8l in my last step, then add 5l of coolant (assuming you want a 50/50 mix). You now have 2l of water and 5l of coolant. So add 3l of water and you're done.

You really only need to measure the coolant. Figure 50% of your cooling system capacity and add that much coolant. Then just keep adding water till the system is up to the proper level. Make sure to run the car for a minute to "burp" the system before you finalize the level.

I usually underfill the system a bit, then let the car cool off overnight in the garage. Before starting the car the next day, I pop the hood and fill up to the "fill cool" line.