Weird Brake Fluid discoloring

[dkl]

I was flushing the brake fluid yesterday and noticed that both rear brakes started with a red-ish/brown-ish color, then stream into your normal used brake fluid color (slightly darken straw color). Has anyone seen this before? What can cause this red-ish/brown-ish discoloring? The fronts look normal, only the rears had this weird initial discoloring.

[jgold47]

Could be that those brakes were not bled properly before and the fluid was just badly discolored

[X5SND]

It Could also be indicative of inner seal wear...when's the last time they were bled? Are they the original calipers? Do you notice any sweating around the piston?

[dkl]

Hmmm...Bled 2 years ago at an independent shop. Original calipers, original brake lines, no sweating around the piston. This weird discoloration went away fairly quickly (about 5-10 seconds from initial bleed)...so it must be something within the calipers.

[upallnight]

Heat from the brake would discolor brake fluid that is closest to the caliper. If you ever tracked a car you will know that racers in the know will bleed the brake after each track session.

[JCL]

Brake fluid can be coloured by the manufacturer when it is made. It is sold in amber, purple, blue, red, and so on.

The brown is more likely to be discolouration from heat and deterioration of the caliper seals, IMO.

[dkl]

Originally Posted by JCL

Brake fluid can be coloured by the manufacturer when it is made. It is sold in amber, purple, blue, red, and so on.

The brown is more likely to be discolouration from heat and deterioration of the caliper seals, IMO.

Thanks JCL. If this is the case, then I would expect to see it in the front as well as those front calipers would mostly likely heat up more than the rears, but the discoloration only occurred in the rears (fronts looked normal)

I've only used OE fluid, so it shouldn't be anything other than the darken straw color (vanilla)

[X5SND]

There's no way the fluid in the rears would turn from heat before the fronts, as majority of braking (and thus heat generation) is done by the fronts. Furthermore, I doubt driving normally around town can produce the kinds of temps needed to do so.

The dark color likely stems from suspended particles from aging seals. If they're the originals like you stated, that puts them around the 7 year mark at the very least. Provided you don't have any scoring on the piston or excessive corrosion around the outer lip, caliper rebuild kits can be had for ~$25 bucks.

[dkl]

Thanks for the inputs. I guessed I'll just have to monitor it more closely in the future.

[bastereo]

Rust, brown brake fluid is rust.