Brakes not working intermittently

mpg50 · Jan 30, 2020

It's a 2010 Prius with about 143,500 miles on it. I got into a wreck so the car was being repaired at a body shop. The car was declared as totaled by insurance company, but the person at the body shop was of the opinion that there is no damage to the mechanical system. After they fixed it up, I took it for a short test drive. While on the freeway, the ABS and traction control lights came on. Within a mile of that, when I tried pressing the brake pedal, it almost didn't work. It felt soft when pressed and went all the way down without slowing down. I managed to pull over to the shoulder. The problem persisted for almost half an hour and then went away on its own (during that time, I didn't turn off the engine to show it to the body shop guy who came to help). After that, it was driven back to the body shop without any issues.

Later, they had a Toyota certified mechanic scan the computer of the vehicle. I was told that they didn't find anything wrong, except that brake fluid level was slightly lower (so they topped it off). They also didn't find any brake fluid leaking. After that, the body shop guy has driven it once or twice, but no sign of any problem. So at this point, he is suggesting that everything is fine, but I am not totally convinced, because I am not sure if the problem has been diagnosed (I think brake fluid level probably wasn't that low that brakes would stop working altogether).

Does anybody have any idea of what could be wrong? I am pretty nervous to drive a car knowing the brakes could suddenly stop working, but I don't know what I could do. Any suggestions?

Thanks.

ChapmanF · Jan 30, 2020

Wouldn't hurt to go through the full bleed procedure using Techstream ... ideally yourself, to be sure no steps are left out.

There's more to the process than a third-party shop might guess, including two passes over the front brakes that bleed different passageways in the actuator.

Techstream offers two bleed options, the short one and the full one. For the full one, you also need the windshield wipers and the cowl out, for access to a bleed screw on the stroke simulator.

It is good to have a wall-powered charger supporting the 12 volt battery while you do it, because (especially if it is your first time) you will spend long enough on the procedure with the ignition on to run very close to out of juice from just the small battery in back.

mpg50 · Jan 30, 2020

ChapmanF said: ↑

Wouldn't hurt to go through the full bleed procedure using Techstream ... ideally yourself, to be sure no steps are left out.

There's more to the process than a third-party shop might guess, including two passes over the front brakes that bleed different passageways in the actuator.

Techstream offers two bleed options, the short one and the full one. For the full one, you also need the windshield wipers and the cowl out, for access to a bleed screw on the stroke simulator.

It is good to have a wall-powered charger supporting the 12 volt battery while you do it, because (especially if it is your first time) you will spend long enough on the procedure with the ignition on to run very close to out of juice from just the small battery in back.
Click to expand...

Thank you for the reply. So you think it is the brake system that actually has issues? I'm worried if it is something else caused by the crash that is indirectly causing this problem (for example, maybe the computer system got messed up or something), but my knowledge of cars (especially something like Prius) is very little, so I'm not sure.

How difficult is it to do the full bleed process for a complete newbie? Any idea how much a shop would charge for it?

ChapmanF · Jan 30, 2020

Well ... there's nothing about it that requires astonishing feats of skill or dexterity. At the same time, I was a complete newbie such a crazy long time ago that I forget too easily how many kinds of "oh, that's just obvious" background stuff accumulates over the years that really wasn't obvious to a newbie.

There are kind of different domains of newbieness that could be involved too. Some people might be pretty comfortable with the basics of how hydraulic brakes work, but less familiar with the idea that they are using a laptop computer to talk to some other computer and tell it to move valves and things. There might be other people who don't have the car familiarity at all, but are totally comfortable using computers in that way (maybe had a robotics class or something). Some people might have neither experience, some might have both.

I'd say if you judge yourself a real newbie, you might not want it to be your first project (you'd really like to trust your brakes, right?). There might be the option, though, if you've got a buddy who has either or both of those kinds of experience, invite them over to watch and help decipher stuff.

I'd think a shop might bill an hour, maybe two, given the tedium of getting the wipers and cowl out of the way, etc.

Brakes not working intermittently

mpg50 New Member

ChapmanF Senior Member

mpg50 New Member

ChapmanF Senior Member

Does this work for Gen3 brake bleed?

An ultra safe rear jacking adapter plate for tire changing and work in brakes

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Brakes not working intermittently

mpg50 New Member

ChapmanF Senior Member

mpg50 New Member

ChapmanF Senior Member

Does this work for Gen3 brake bleed?

An ultra safe rear jacking adapter plate for tire changing and work in brakes

2013 Prius driver brake light not working

2012 high brake light intermittently works

Brake work - DIY??