Is a brake fluid flush necessary? and what is it for?

 

Yes it is a good idea...brake fluid oxidizes and acts with condensation in the lines to turn dark brown over time. Fresh fluid is necessary to keep condensation out of the system. Most service centers will just sue a syringe to suck out the old fluid and refill with new. The dealer may actually crack open all wheel cylinders and bleed the system...I'm sure some Lexus techs will confirm the recommended procedure.

 

Brake Fluid is hygroscopic (absorbs moisture) and becomes contaminated with water.
Water in the brakes system rusts steel brake lines and can freeze in extreme temps.
Before Anti-Lock Brakes were common all the brake lines were quite large in diameter.
The ABS unit has many extremely small diameter pipes and fittings inside. While it
was always reasonable to flush out old fluid it is now a virtual requirement.

 

The other reason you should replace the brake fluid is that its boiling point drops as it absorbs water. This will mean that the fluid will boil at a lower temperature, sometimes to the point where it can boil in the calipers and/or brake lines during heavy use and cause vapor lock – this severely reduces the stopping power of the brake system, usually at the time when you need it most!

 

What they said. If your brake fluid isn't clear, or at least translucent, replace it.