How to bleed brake on 2005 Prius?

[hsujohn]

Hello:

I recently bought a 2005 Prius(out of factory warranty) and felt brake is not so good, so I did the brake bleeding job with my friend, later felt brakes is even more soft and hard to stop, and also has a beeping sound now, I later searched on internet, only found one person said from 2004 and up prius need specail tool to bleed?

So can anyone help me on this without going to "stealer"?



thank you so much!!!!!

[hobbit]

Ohboy. Yes, bleeding the Prius brake system is inordinately complex,
because your foot doesn't push fluid around in the traditional way.
The "special tool" is the handheld tester, aka Mastertech scantool,
which allows actuation of certain solenoids to open fluid paths in
ways that make sense for bleeding but not during regular operation.
.
In the interest of saving time and headache, you might want to just
take it to the stealer this time and then read up on the whole system
and process for dealing with it before going after it again...
.
_H*

[galaxee]

the normal braking on a prius feels very different from a regular car.

and bleeding the system is a far different job on a prius than on a regular car- in fact it's kind of a PITA even for an experienced tech. the system is touchy. and you do need the toyota scantool to do the job, so this has to go to the dealer.

the beeping sound means you don't want to drive it until you've got this taken care of... please don't drive it in this condition. that is dangerous and nobody wants you to get hurt.

good luck

[IsrAmeriPrius]

<div class='quotetop'>QUOTE(hsujohn @ Nov 22 2006, 10:31 PM) [snapback]353401[/snapback]</div>

...and felt brake is not so good, so I did the brake bleeding job with my friend...
[/b]

There is no mechanical connection between the brake pedal and the brake master cylinder in the Prius. When traveling at a speed over eight miles per hour, the braking is accomplished by regenerating electricity, not by conventional friction brakes. It is a complex drive, or rather brake, by wire system. The feeling you experienced had nothing to do with air in the brake lines. That is how the pedal normally feels. I am afraid that the current symptoms that you are describing are the result of insufficient amount of hydraulic fluid in the brake system.

[LongRun]

So, are you saying that if you are driving down the road and the engine quits running and you have not electrical power, a dead or low main battery, then you have no brakes? If I roll my Prius forward in the driveway with the system off I have no brakes?

I wonder if you can blead the rear brakes by having the system on and just opening the bleader screws and let the brake fluid run out. The brake assist feature will come on when the static pressure drops and start putting pressure on the system which will force it out the bleader screw. It works that way on my 03 4Runner. If so then there is only the front brakes to figure out.

[galaxee]

<div class='quotetop'>QUOTE(LongRun @ Nov 23 2006, 12:48 PM) [snapback]353517[/snapback]</div>

So, are you saying that if you are driving down the road and the engine quits running and you have not electrical power, a dead or low main battery, then you have no brakes? If I roll my Prius forward in the driveway with the system off I have no brakes?
[/b]

well... there's the "engine off" and the "system off" and they are two entirely different things. the brakes are in no way interconnected with the engine running. if you have a dead main battery, well, the car won't start so brakes won't exactly be a concern. however, should some massive failure occur there is a backup power supply which will allow you to get off the road and stop.

I wonder if you can blead the rear brakes by having the system on and just opening the bleader screws and let the brake fluid run out. The brake assist feature will come on when the static pressure drops and start putting pressure on the system which will force it out the bleader screw. It works that way on my 03 4Runner. If so then there is only the front brakes to figure out.
[/b]

the prius' brake system is NOTHING LIKE the 4runner or any other conventional vehicle! this is exactly the problem here. people are assuming the brake system is like the one in a conventional car and this is NOT the case. if you open the rear bleeder screws without a scantool you're going to suck more air into the system than the brake fluid you'd drain.

[hsujohn]

oh damn, anyone know that would reguler shop have "master tech tool" or only Toyota dealer has? Don't really want to get ripped off, or if that tool is not too much to buy, can anyone point out where I can get it?

thanks for everyone's help!!!!! Have a nice holiday!! :)

John

[galaxee]

eh, john, hate to tell you but this is a dealer only (for the most part- some indy shops may spring the cash) tool that costs multiple thousands of dollars

my husband works at one of the top 2 busiest prius shops in the country, so he and all his guys have plenty of experience and can do this more quickly than someone with zero experience. find a toyota shop with high prius volume, they're more likely to be talked into charging you a little less than someone who's never done it before. on the west coast, longo is the only shop that compares to where DH works over here.

if you want to call around to local shops and try your luck there, ask them if they have the toyota scantool. any other scantool will not access the hybrid specific functions. keep in mind that someone who has not done this before could have quite a bit of trouble doing so, at a dealer or indy shop.

happy thanksgiving (and sorry for the unhappy news), and let us know how things work out.

[hobbit]

Okay, to lay this to rest quickly, you should read this PDF.
I am hoping that some of the independent scantool makers [notably
AutoEnginuity, who seem to be closest to getting the Toyota enhanced
stuff in proper order] will have this functionality in their own
products soon, for an order of magnitude less $$ than Mastertech.
.
I had to put a Prius through the "linear valve zero offset calibration"
dance recently. The instructions aren't too detailed; you invoke the
function from the scantool and wait. But under the covers I heard
an *elaborate* dance going on with firing various solenoids and
pressurizing various wheel brakes individually and letting them
back off again and running the accumulator, and finally the ABS
light changed its blink rate and it was done. Weird stuff.
.
Oh, this pic of the brake system might help, too.
.
_H*

[Gen2]

<div class='quotetop'>QUOTE(LongRun @ Nov 23 2006, 09:48 AM) [snapback]353517[/snapback]</div>

So, are you saying that if you are driving down the road and the engine quits running and you have not electrical power, a dead or low main battery, then you have no brakes? If I roll my Prius forward in the driveway with the system off I have no brakes?

I wonder if you can blead the rear brakes by having the system on and just opening the bleader screws and let the brake fluid run out. The brake assist feature will come on when the static pressure drops and start putting pressure on the system which will force it out the bleader screw. It works that way on my 03 4Runner. If so then there is only the front brakes to figure out.
[/b]

If I remember correctly, you will still have the hydraulic brakes, what you wll lose is control over the ABS function of the antilock brakes and the regeneration feature, but the car will still stop.

I recently wanted to change the brake fluid myself and despite havinf been a mechanic in a previous life I was happy to pay the dealership to do something this critical for me.