Devon West

My coolant turned brown. It was blue. It’s not a moly like mixture as of if oil was in it. I’m not sure any help is welcome. 2014 e550
previous owner had orangish coolant in it then i replaced it with blue. Hopefully that’s why it’s that color as of now because it mixed

Left Coast Geek

you are right on the cusp year when Mercedes switched from their old 325.0 blue coolant to the new 325.5 violet-pink stuff. THEY ARE NOT MIXABLE, and other random generic coolants that don't meet the correct spec for your engine can have bad effects like gumming everything up. I would do a thorough cooling system flush and refill it with the correct spec.

rapidoxidation

What does your oil look like?
How about your transmission fluid?

bmwpowere36m3

I don't know of an approved orange coolant for MB.... I would start my thoroughly flushing the coolant, draining both the block and radiator. Then clean the system with approved detergent and re-flush. Finally fill with approved G48 or G05 coolant (either blue or yellowish-clear).

Assuming you're sure its not oil from a failing HG or cooler...

Devon West

oil is good. How do i check trans fluid

Left Coast Geek

trans fluid is more challenging. you have to jack the car up so its dead level, and open up the drain plug and catch what dribbles out. to change or add ATF, you need a pump setup to pump it up into the transmission through the drain plug.

this video goes through the whole change and refill process

this one shows how you check the level, and in the process get some drips out you can catch in a clean container to inspect

CaliBenzDriver

Practically how long do you keep your OEM coolant before replacing it with equivalent specs?

Is the extended flush interval what eats into the dissimilar metal of the transmission heat-exchanger ??
🤔

Left Coast Geek

both the MY10 and MY16 booklets say for regular E class (non-AMG), every 150,000 miles or 15 years for coolant change. They of course say to check it every 10K as part of the "A" service, and if the level is low to investigate why and repair as needed.

Mohd Saadi

You need to check your oil level to be sure that there's no coolant in it. And open your oil filling cap and be sure there's nothing on the cap "like some milky".
So no coolant in oil + the car isn't over heating then your head gasket is fine
Oil in coolant reservoir. If there's no symptom of bad head gasket your oil cooler should be replaced
And you should flush the system like 10 times 😢