Sobrut911

I have a 2011 TTS with 9500 miles/2 years old as of 4/13. I noticed in the maintenance manual that the brake fluid should be changed every 2 years regardless of mileage. I was wondering if it is really necessary, especially where car has never been tracked. Local dealer sent coupon for $139.95 brake flush, so I guess I'll have it done when I have the yearly oil change done which probably also really doesn't have to be done.

jhbrennan

The last thing you want is water in the brake fluid and since brake fluid is hygroscopic, changing every 2 years is recommended...even if you don't track.

jparker36

If the car isn't getting mileage, oil at least once a year, and brake fluid every 2 years is a good idea. You can get both done for less than that price if you go to an indie shop vs the dealership if that's your concern.

Doc GTO

Not a hard job to do and it keeps the fluid water free. Worth it.

fskof

YES changing the brake fluid is cheaper and easier then replacing your calipers due to corrosion. Buy the Motive bleeder and do it yourself. Very easy to do!

It is recommended to change your brake fluid often. It will increase performance of your braking system, as well as prolong the life of your parts. With DOT-3 and DOT-4 brake fluids, over time water condenses in the system forming pockets that can be corrosive to parts. As more water enters the brake fluid, the boiling point reduces and eventually cooks at high temperatures turning into gas. When this process takes place in your braking system you may end up with a squishy feeling pedal or no brakes at all.

Here is some info I found: http://www.dvatp.com/bmw/diy/brake_fluid_flush/

Why Change Brake Fluid
Brake fluid is hygroscopic. That means when exposed to air brake fluid will absorb the ambient moisture from the air. This contamination lowers the boiling point of the fluid and thus reduces the upper temperature limit tolerance of the brake system. In the worse case scenario contamination of the brake fluid can result in a near complete loss of braking power. Truth be told, however, most street cars are never driven in a way that will test that extreme.

The real threat from the absorption of moisture into the fluid on a street car is corrosion. The stock BMW brake calipers are cast iron and cast iron does not react nicely with water over time. If you allow the fluid to remain in the system too long the water can cause pitting on the internal surfaces of the caliper and piston and in an extreme case cause the piston to bind -- which translates into major brake system work and a commensurate hit to the wallet.

Of course, the absorption of moisture is not the only reason to change fluid. Brake fluid absorbs a lot of heat that is transmitted through the caliper body during repeated braking action. Over time, the heat cycles cause the fluid to break down and this again reduces its boiling point. This breakdown is most evident in the change of fluid color over time. The fluid is, for lack of a better term, "burnt".

speed21

I'd run through a good synthetic fluid...Motul etc. It makes a nice difference in the pedal feel.

Sobrut911

Thanks for providing me with the detailed explanations. I'll be changing the brake fluid every 2 years regardless of mileage.