will rusty brake fluid damage wheel cylinders or the master cylinder?
Why take a chance ? Have a shop replace the fluid as you are probably past due anyway. Car not starting is annoying - car not stopping is catastrophic .
If your brake fluid is rusty, it’s way overdue to be changed!! Change it ASAP!!!
I will 3rd that! YES rusty brake fluid will damage things! It is also a hint that something is already damaged!
Brake fluid doesn’t rust, the stuff it touches does, so as the others have said, you’re way overdue for a full brake fluid change, both in the reservoir and by bleeding all the wheels.