Stupid question about changing brake fluid

[beezer]

I understand that changing the brake fluid is the same as bleeding the lines. Here's the stupid question. Do you keep adding the new fluid to the master cylinder like you do when bleeding the lines or do you go keep going until there is no more fluid left then add the new fluid? Sorrry new to working on cars. Beezer

[mikec]

Keep adding the fluid to keep it above the low line. If it gets too low in the master cylinder, you risk air entering the lines.

From what I've seen, the fastest way is to suck as much out as you can from the master cylinder, refill with new fluid, then start the bleeding process.

If I'm wrong about any of this, someone lemme know!

[vrg3]

Yeah, don't let the master cylinder reservoir get too low! Air that enters the system at that point is very hard to get out.

Do what Mike said -- use a turkey baster or syringe to suck the fluid out of the master cylinder, but not so low as to risk exposing the ports at the bottom to air. Then fill it to the top with new fluid and keep topping it up as you bleed the rest of the system following the specified bleeding order. Just make sure that at the end the fluid is up at the 'full' mark on the reservoir and not above.

[scottzg]

I take the whole brake fluid bottle and flip it upside down with a card over the top. Then i drop it into the fluid reservoir. The vaccuum in the bottle holds it in place until the reservoir is too low. I've also got a little plastic hose that attaches to a 1gallon milk jug and the bleeder, and I use a pipe wrench propped against the seat. I can bleed all 4 brakes by myself in about 15 minutes.