How avoid injecting old brake fluid into calipers with piston reseat

Before you start all this open a front caliper and remove resvoir top . Once the fluid gets down to the last two or three drops until it disappears and you can't see it in the reservoir anymore add brand new fluid . Let it drip a few more minutes and close that fitting up and go to the other side and open the other fitting let it drip 5 min . Now you have new fluid from the reservoir out of the front calipers and front lines. That don't take much . I'm using dot 5 in one gen2 now. You won't mix the two of careful .

 

Has the brake fluid ever been changed, to your knowledge?

Maybe get the dealership to do that, and then don't touch the bleed screws when pushing the piston back in.

 

Changing old brake fluid in modern cars is unnecessary and some believe that the start of a very expensive brake booster failure began after a brake fluid flush... So if you don't want to spend thousands on a new booster pump keep it simple.

If you need proof to change or not to change ---> use a moisture test strip to see how much moisture is in the brake fluid...

As for the rest of it, when you push the pistons in that means the reservoir fills up and in modern cars that rarely have problems with brake fluid you can correlate brake fluid level being low to sigignifican brake pad wear (unless a dummy topped off the fluid level) and when you put the new brake pads on the fluid returns to normal. Thus a smart mechanic never has to bother with changing brake fluid levels because they use it to determine brake pad wear and when new pads are installed the fluid in reservoir returning to perfect level is further confirmation the system is working properly.

Gen2 Prius are amazing in that regard. I'm got 287K miles out of original front brake pads and still on original fluid that returned to a perfect level once the brake pads were replaced.

 

I don't understand how your going to prevent brake fluid from entering the front brake calipers; if your going to press the brake pedal? Please clarify your thinking on this; because brakes are designed to apply pressure on all four corners, with or without power - It's a safety design.
Once your finished with the brakes; you NEED the pump the brake pedal to seat the pads - otherwise you won't have any brakes for the first few pumps. If your young and just press the brake pedal to the floor boards, you'll never stop. Us old timers are thought to pump the brakes during failure.
Don't need no fancy power brakes or ABS

 

I think the problem with OP is overthinking... It takes 15-20 minutes per axle to change brake pads from start to finish. I always talk about that with people who tell me they just got ripped off for having brakes changed that weren't even worn out yet! Their mechanic was making more off them per hour than lawyers charge their clients. It's so wrong!

 

My brother runs a shop and hires idiots - because he's too cheap to pay anyone that knows anything. The kids he hire already knows EVERYTHING. This kid does a brake job and is suppose to get a sign-off before putting the wheels back on. He finishes the job in record time, without sign-off. Backs the car out of the stall, can't stop, and hits a parked car.

ONE guess what he didn't do?????

I had to rub it in; Asked the smart asset why he didn't go after the parking brakes or pump the pedal????????? You did adjust the parking brakes; didn't you? It was a Fred Flintstones moment; watching him try to stop the car with his feet. I was just lucky to be there when that happened; because I've told my brother on multiple occasions to just pay the mechanics a little bit more for the good ones - that'll improve business, lower your insurance rates, and your ulcers may even go away.

 

You'd think it'd be obvious that you want to pump the brake pedal a few times so it feels normal again in case the dude that hired you checks out how its going? It's weird these days kids don't grow up worrying about getting in trouble in order to avoid it. They just straight up get in trouble without worrying about nothing.

 

If you want to "avoid injecting old brake fluid into calipers", flush the line of old brake fluid first. Pop the cover off the brake fluid reservoir, to prevent a vacuum, as fluid level recedes. Now simply loosen the bleeder, and gravity will do the rest.

 

When the brake fluid's replaced it's drawn from the bleed screws at the four calipers. The fluid there's as clean as the rest.