replacing brake pads/rotors
 

ok i feel pretty comfortable doing a brake replacement, but i just got a haynes manual for the mustang and on the brake replacement section it says: " before replacing the pads/rotors siphon out half of the brake fluid from the master cylinder" is this necessary? Ive done it a few times on a few different cars and Ive never done this. Have I been doing them wrong, is there anything that can go wrong or fail if this isnt done?

I've never done it, personally

When i did mine i did not do it.

The Question is, has there any problems since you didn't do it?

I didnt do that when i replaced my pads and rotors. No issues. I did bleed my brake system real nice so that mostly clean fluid was left in the system when i was done.

It's not needed. The reason they say that is because of the possibility of brake fluid over flowing from the resivor when you compress the brake caliper piston or when you pump the brake pedal to bleed the brakes. I actually would advise to keep as much fluid in the resiviour as possible to avoid allowing air to enter the system. You never want to let the resivour tank get less than half full of fresh brake fluid. If you let any air enter though the tank you'll have lots of work ahead of you. The brake fluid I use is Motul RBF 600 and is $15 a bottle, I can't even afford to flush and flush the brake due to air.

What he said...it will want to overflow when you compress the caliper.

Yep no need to do it. And you most likely need to swap brake fluid anyhow so drain that shit.