Bleeding when pushing the front brake's pistons

If this is your first time doing brakes, I'd strongly suggest having a EXPERIENCED friend; who knows what they're doing help you out for your first time. Brakes are a pretty important component of your car and needs to function properly!!! If you don't have a friend like that, take the car to a professional. You don't know, what your don't know!
NO you DO NOT crack the bleed valve on your calibers! That's a surefire way of getting air into your braking system. There shouldn't be any junk behind your caliber piston, if you properly maintain your braking system. Brake systems flush-out every 3-5 years; Toyota doesn't recommend it but other OEM's like VW & Honda do.

I can watch plenty of videos on how to defuse a bomb; but that doesn't mean I would want to - the stakes are too high.....

Just my 2-cents.......

 

I disagree... Brake systems are very simple and straight forward and the fear related to maintaining them causes so called "Professionals" to charge hundreds of dollars for something that's a super easy 20 min job once you've done it enough times. It's not much different then changing batteries in an expensive machine. And changing brake pads most often doesn't require new rotors or bleeding the lines... Of course if you want to tru$t the expert$ about $afety...

 

Toyota USA simply says nothing about brake fluid replacement. For our newly purchased 2010 Prius, Toyota Canada also said nothing. But I happened to notice, looking at TC’s maintenance guide for model year 2014 Prius: they’d added:

Replace brake fluid, every 48k kms or tri-yearly, whichever comes first.

^ I’d concur though, every 4~5 years is reasonable.

There’s a couple of brake related links in my signature, 3rd gen specific but with some universally relevant bits.

The link about rear brake drag has general advice about DIY Prius brake maintenance “tactics”, to avoid things like the car trying to pressurize the brake hydraulic system while the caliper’s off the rotor, which can be disastrous , piston pushed out of caliper. Another issue is the car detecting excess brake pedal travel after brake pad replacement, and how to avoid that.

There’s another link about DIY brake fluid replacement, again 3rd gen specific but maybe worth a read.

(On a phone turn it landscape to see signatures)

Attached is 2nd gen Repair Manual brake excerpt:

 

As you can see, there are differences of opinion.

For what it's worth, I'm in the bleeders open to push pistons back camp. As a younger fella I used to just mash them back and force the fluid back up into the head end, but that was back in the days when the head end was just a bare-bones master cylinder and not an ABS actuator containing dozens of tiny delicate electronic valves and with a four-figure replacement cost.

As I don't want to be letting air in while I do it, I'll take a length of clear tubing long enough to make a loop, pour some brake fluid into it, wiggle the end onto the bleeder nipple before opening it, and loop the tubing upward from the caliper and then down into a catch bottle. That way when I crack the bleeder open, if anything goes inward (which isn't likely anyway; I'm going to push on the piston, not pull it*) it'll be the fluid in the tube.

By contrast, I'm not as fastidious about total brake fluid replacement as some. I dunk a test strip into mine now and then. If I change pads, I'll make up for the fluid I pushed out at the bleeders with fresh fluid into the reservoir. Once or twice I've noticed honk noises and done a bit of bleeding to alleviate those; the amount of fluid that goes out I'll make up with fresh at the reservoir. I tend to think those things add up to "good enough" fluid replacement, just through doing things I was going to do anyway.



* when you're done pushing and take your push tool off, the piston may rebound by maybe 0.3 mm, just the rubber piston seal doing the same thing it does in normal use when it retracts the piston, only in reverse. So there'll be a little bit of backward flow in the tube at that moment. By that time the tube should already be filled with fluid you pushed out, even if you didn't pre-fill it.

 

@Prius2006GuitarGuy; did you see that procedure in one of your 25 videos????? That would be an acceptable way of keeping air out of your brake lines. While some would claim how easy it is; You don't know, what you don't know.....

Good Luck........

 

brakes are easy on the Prius, no need to open the bleeder valve unless you're replacing the caliper or hoses. I've friends who tried servicing their own brakes and messed up but they're easily mitigated. The rear drum is more work compared to the disc brake in the front.

I just recently purchased a Ford Escape hybrid and the brake calipers locked up, turned out to be the hose. It needs an ABS bleed (scan tool - I used Forscan) to fix. There were some videos on youtube that's basically wrong about these hybrids, so be careful. I'll be posting soon my video about the ABS bleed on my channel.

 

The OP should be aware that while at the wheels the mechanical parts of the brakes are just like on other cars, in terms of controlling and keeping track of the fluid in the system the Prius is finicky. Flushing the brake fluid, according to the manual anyway, requires software control of the ABS unit. Also that bleeding too much fluid out, for any reason, while the battery is attached may set a code.

 

While it's certainly possible to leave bleed valves closed while pressing pistons back, the reason I recommend opening them for that comes down to peace of mind on those odd occasions where some other brake problem, like a mysteriously dragging brake, crops up after you have done your pad replacement.

If you know for sure that nothing you did involved pushing old fluid back through the actuator valves, you can pretty much confidently rule out actuator contamination as a likely cause of your new problem. If you can't rule that out, you have to keep it on the list of possibilities and rule it out with diagnostic testing, which takes longer and might call for more specialized tools (like LSPV gauges) than you have on hand. You can also be kicking yourself pretty hard while figuring out whether that is or isn't what happened. Even if it turns out not to be, you still had to go through that. It's better for peace of mind to not have to.