Q: My brakes are overheating; could the brake fluid be contaminated?

If your brake fluid boiled during this or any past overheating incidents, then yes, the fluid is likely contaminated with air and other gases. Brake fluid is hygroscopic, and a consequence of that is when the fluid gets hotter than 212° F, the moisture in the fluid boils which creates air bubbles or entrained gases. That air is then trapped within the brake lines and reduces braking power because these gases are compressible while brake fluid itself is not. Severe overheating could degrade the rubber seals in the caliper as well. The solution to your entrained air problem is to simply bleed the brake system. If you would like some professional assistance with this issue, a certified technician, such as one from YourMechanic, can bleed your brakes for you.