What's the best way of flushing out the coolant system? I still have old chocolate looking stuff in the expansion bottle. No leaks apparent from the drip hole at the bottom of the water pump and yes, it is not blocked! Its still residue from before. I didn't use a flushing chemical. Is that the way to go?

Hi there, this is waht I do (every two years):
For the expansion bottle take it out and wash it, for cleaning inside stain use a mixture of soap and clean sand and shake it, then rinse until all the sand is gone.
For the system, drain it an fill wit tap water, run to operation temp, let it cool drain, and repeat until wather comes clear, finally fill with demineralized water and your favorite coolant flavor.
Best regards
JAP

What JAP said.

But you'll see that it is bloody difficult to clean the clear plastic tube on the expansion bottle. If it really irks you to see the discoloured tube, replace it.

If you have had oil in the water system as a cause of the chocolate you need detergent to get it out, there is a standard detergent powder available from your friendly Mercedes Benz dealer which is specifically intended to de-oil the rad and water system. After running the stuff around the system it is drained and flushed with tap water and then refilled with the recommended mix of anti freeze and water to restore freeze resistance and anti corrosion chemicals.
Regards,
K-BIKE

That's right K-BIKE Landrover also do a similar item used to clean out rads and intercoolers from oil contamination.


BIG D