Brake fluid Mercedes dealer DOT4 green

[jt20]

1995 E300

car has history of service at the MB dealer.

Recently installed rear brakes and flushed the system.

DOT4 brake fluid

Initially, the fluid leaving the calipers was typical amber (ish) and dirty.

Once I got that out, green fluid from the reservoir came through.



What is this green fluid? Pentosin? MB formula from the dealer?

Is it dyed so that the color will change as it takes on moisture? Or did I just have 2 different fluids and a poorly serviced system?

[jt20]

I should have searched better.

Green Brake Fluid

Green brake fluid

[BillGrissom]

Interesting. I read the links, but they don't answer the "why green?" question, just speculation. I use DOT 5 (silicone) in my two 300D's. It is dyed blue to distinguish. I was concerned that it turns amber over time, but read that is normal and just the dye fading. Actually, DOT 5 is a performance rating. Only recently could any glycol fluids meet that, and they are distinguished by labeling "5.1", though surely that causes confusion. Don't believe the myth that bad things happen if silicone and glycol mix, but you can read actual tests on the web and ignore all the counter-man claims.

[jt20]

Thats true, not completely they didnt.

What worked for me was the suggestion that the mixture of the blue DOT4 and the amber was responsible. This seems reasonable since the blue could have been in the ABS system after being flushed at some previous point.

Bah... I don't know.

The green fluid was very clean looking. I can't find any dot 3 or 4 that is green. And the ATE super blue has been banned since 2013ish cuz it has dyes. .... so why would there be other dot 3/4 that have different color dyes?

I am not buying the copper / brass argument.

[jt20]

Originally Posted by BillGrissom

I was concerned that it turns amber over time, but read that is normal and just the dye fading. Actually, DOT 5 is a performance rating.

So, you have actually witnessed these fluids change color over time? that is very helpful. thank you.

[BillGrissom]

Yes, after several years. The fluid then has a very faint yellow or amber, not the strong blue original. I have read that can happen on the shelf, so don't be alarmed if you buy old military DOT 5 in a 1 gal metal can. I have twice, but it still came out fairly blue. BTW, silicone brake fluid was (still is?) required for military vehicles, termed BFS = brake fluid silicone.

[jt20]

After filing the reservoir with clear DOT 4 and flushing the rear, the reservoir is now green again and dirty.

I doubt this much could come from just the front brakes.

Does the ABS cycle fluid through it even when not being engaged?

I have not had the ABS kick in since I did the rears.

[Zulfiqar]

Originally Posted by jt20

After filing the reservoir with clear DOT 4 and flushing the rear, the reservoir is now green again and dirty.

I doubt this much could come from just the front brakes.

Does the ABS cycle fluid through it even when not being engaged?

I have not had the ABS kick in since I did the rears.

brake fluid cycles a bit when you press the pedal - the green you are seeing is most probably residual fluid from the ABS unit or the master cylinder. My car also had that and it took 2 flushes 6 months apart to get rid of the moldy green colored brake fluid.