Cummins600

My Brake fluid was lookin' nasty at 40k miles so I had a shop flush the system. They pointed out that the fluid seemed kind of oily with a light residue/film in the master reservoir. Had the DOT 3 replaced and hoping the new fluid might brake-down the film. Any ideas on this? Could it be more than just old fluid?

P.S. I'm on a roll this week with issues.

Hemi Cat

You did the right thing by flushing it. Without actually seeing the fluid, I couldn't say what it was. Is the rubber diaphram on the cap swelled up or deformed? If it is, it would indicate a petrolium product. Best advice now is to monitor it for more breakdown or swelling of the rubber diaphram.

Lightman

Cummins600 my brake fluid did the same thing after towing 9000lbs from OH to FL and back. I think it could have been the times I had to ride the brakes down some of those steep grades (no exhaust brake) to control my speed. The brake fluid was noticeably darker and brownish in the reservoir. I used my motive brake bleeder and flushed all the fluid with valvoline synpower dot 3/4 I believe it was from Advance auto. The fluid is now clear/clean still and the brake feel did seem to improve slightly with the new fluid. Hopefully yours is fine now too.

CRXsi

I have seen this 'residue' frequently on cars before their first flushes. It could be sevseral things:
-could be the fluid has started to congeal (I have seen this in higher mileage brake fluid)
-could be something added in that wasn't supposed to be (unlikely)
***likely that it is some of the silicone assy lube used during the manufacturing process of the Master cylinder, calipers, and anything else with rubber seals internally in the brake system (including abs solenoids, etc). What tends to happen is either slowly over time the silicone grease dilutes with brake fluid and migrates to higher areas or with decent braking and brake fluid that gets very warm the silicone turns more liquidy and disperses to other areas. Wouldn't be too concerned unless you are experiencing other problems***

Cummins600

Thanks for the tips. I does seem like it could be some silicone mixed in the DOT 3. Maybe when the brake get pretty hot some of us will have this event with the brake fluid. My brakes work grate as day one. Just wanted the get rid of the contaminated looking fluid. I might flush them again in the next three months to try and remove any possible remaining foreign junk.