Replacing brake fluid and bleeding brakes on a GEN II Prius without Techstream

So, speaking of brakes, the Gen 2 I have been working now runs and seems to be doing most things correctly. However, it has Brake, ABS, and low tire pressure lights. I'm guessing the low tire is dead sensor battery as it's a 2007 and I don't know what the Maintenance History is. But, the prior owner put tape over the warning light. The Brake light I think means I got air in the lines when I emptied the brake reservoir. I haven't done any hard braking but the pedal feel seems good. Would that trigger the ABS warning as well? I have Dr Prius app, Torque Pro app, and a bluetooth OBD2 that works with those two apps. Any suggestions are appreciated. Also, is there a battery in the spare tire for pressure reading?

 

I read 1.2L somewhere on an auto supply site but who knows whether that's correct. My owner's manual doesn't say which I guess is probably not unusual.

 

Great post! Thank you !!

 

WHY....Put the Prius in diagnostic mode and what does this mean..?
I tried this several times but my Prius 2007 wont go into that mode....

 

Introduced in Gen 3 Prius was something called "electronically-controlled brake system invalid mode", which is not the same as "diagnostic mode", and is useful when doing some brake bleeding operations without Techstream.

Here in the Gen 2 forum, there is no equivalent "ECB invalid mode" mentioned anywhere in the Gen 2 repair manual (unless there has been an online update newer than the copy I'm looking at.) In fact, the Gen 2 repair manual simply offers no without-Techstream alternative instructions for bleeding or fluid replacement.

The "diagnostic mode" zak.kapoor is talking about is something different; it is available in at least Gen 1 to Gen 3 Prius (about Gen 4, I simply don't know), and it is a way of retrieving trouble codes from some of the car's ECUs when a code scanner is not available. Having a jumper between those two pins will cause various warning lights on the dash to blink. Those that have no trouble code to report will blink at a steady fast rate, while any that have codes to report will blink more slowly, and by counting the blinks you can obtain two-digit trouble codes to look up in the manual.

On cars with MFDs, there is also a diagnostic mode for the MFD that allows certain operations like switch checks and retrieval of specialized trouble codes for the infotainment system (not for the car's other systems, disappointingly enough). Instructions can be found for entering that mode by fiddling with the headlight switch or by tapping the touch screen in certain locations. Using a jumper wire to put the ECUs in code-blink mode generally also puts the MFD into that diag mode. (I remember on my Gen 1, using the headlights or screen-tapping methods would put the MFD in diag mode in English, while the jumper method would put it in the same mode but in Japanese.)

On your 2007, you should definitely be able to start the code-blink mode with a jumper between pins 4 and 13. If there are no codes to be reported, you should at least see several dash warning lights go to a steady fast blink. If that isn't happening, recheck your counting of pins (and the orientation of the connector, and if you are looking at a diagram, whether the diagram is of the cable end or of the connector).



Irrespective of any connection to brake bleeding, it is useful to perfect this skill, because sometimes you may get a warning light during a journey when you have no scan tool available, and this often allows you to find out what is wrong.

But back to the question at hand: there is nothing in the repair manual to suggest that this mode is of any use during brake bleeding, or that it is in any way equivalent to the "ECB invalid mode" present in Gen 3. It is possible that zak.kapoor found some obscure document somewhere that said that it is. In that case, it will be great for that poster to reply and cite the source, and that would be very useful to have.

At the same time, it's also possible that zak.kapoor simply assumed, or guessed, or made up, some connection between this mode and Gen 3's ECB invalid mode, or found some internet source where somebody else had assumed it, or guessed, or made it up, and just repeated that. There probably are few Prius topics where more apocryphal internet procedures are floating around than for bleeding the brakes.

 

I know alternatively ABS codes can be retrieved as blink codes and cleared at the OBD2 socket. A Special Service Tool, SST (a fancy name for a bridging wire), is indeed inserted between pins 4 and 13 on the 16 pin OBD2 socket. When the ignition is switched on, the ABS/VSC light will flash. If the brake pedal is then pressed eight times in five seconds, followed by the SST being removed – all ABS/VSC codes will be erased. I did this when I got all lights flashing after caliper rebuild...

But I guess that's nothing new....

 

I have tried to do the steps but I made a mistake by not adding fluid so the pump sucked air and stoped working , I added fluid and now trying to bleed all 4 brakes again but no fluid coming on the rare brakes and very low pressure one on front , I also hear the pump like it’s Gina start but it doesn’t , I saw somewhere someone talking about valve locked but not sure how to unlock them , any thoughts will be much appreciated

 

I have tried to do the steps but I made a mistake by not adding fluid so the pump sucked air and stoped working , I added fluid and now trying to bleed all 4 brakes again but no fluid coming on the rare brakes and very low pressure one on front , I also hear the pump like it’s Gina start but it doesn’t , I saw somewhere someone talking about valve locked but not sure how to unlock them , any thoughts will be much appreciated

 

You'll need a Windows laptop, a J2534 dongle, and Techstream software. There are utilities within Techstream for air bleeding the brakes, including one that applies when air got into the head end itself. It will take a while to complete, and you should probably have a 12 volt supply or charger paralleled on the car battery before you start to make sure the battery holds up during the whole procedure. The utility in Techstream will be working the pump and all the necessary valves in weird sequences for chasing all the air out of the actuator passages. To my knowledge, there is no non-Techstream alternative for that procedure.

 

I wonder whether it would be possible to apply limited air pressure to the opening of the fluid reservoir. If the hydraulic piston was in the correct position and the bleed nipples were opened sequentially, could slight air pressure duplicate the brake pump function? I don't know enough about the internals of the brake system to answer that. Clearly, TechStream is the easiest option.

 

Take a look at the eleven solenoid valves in that system:



Those are electronically controlled by the brake/skid ECU. You don't have a way to work those valves in the right weird sequences to chase all the air out of there, other than using Techstream to tell the brake ECU to do it.

 

That makes it look like it would not be worth even trying my idea. Would the air eventually exit one way or the other through use? More of a curiosity than anything else. You'd obviously be operating at low speed for awhile in a controlled area.

 

I can't think of any particular reason to assume it would.

 

As far as a i know....bleeding is the only way to get the air out....it's a closed system..

 

Hey there,

so, I´m hijacking this thread to get some concise information about brake bleeding.
I just replaced brake pads, brake disc and the whole brake caliper on both rear wheels, because everything was completely stuck.
I´ve only done brake replacement on the front wheels of our ford galaxy, which went pretty smoothly.
I already watched a dozen tutorials and got a ton of info on a german prius site, it took me 3 weeks to get it all done so far, but that mostly included waiting times, because I kept needing more parts and tools I was missing.

So, now I finally got everything installed fine, but the brakes seem to be stuck somewhere, when I did a test drive: I could hear a very distinct grinding sounds it felt like the car was braking a lot more than usual through recuperation, when stepping off the gas pedal and fuel consumption was twice as high.

At first I assumed I may have adjusted the parking brakes to tight, but after loosening them quite a bit without any change, I did some more research and I think the problem might be the brake piston coming out too far.
But thats something I can´t find any info on: How far exactly should they come out, when the car is standing and I´m not using the brakes?
I assume they should retract completely into the cylinder, but if you google that, you only end up with people having pushed them out completely or the pistons not retracting at all...

I realize the brake pads shouldn´t have to travel far, so its normal that they are pretty snug on the brake discs, but it seems they are completely flat on the discs to me, I can´t even get the tip of a flat head screw driver between brake pads and brake discs.

Thats something I hate about trying to get instructions online, because they are often kind of vague: Instead of saying "between 1 and 3 mm" it just says "there should only be a small way to travel for the brake pads"...

Or how loose do the parking brake need to be adjusted, so the wheel can still "turn with only a little bit of resistance".
How much resistance is "a little bit" is VERY subjective, especially if its the first time you do this...

I´m not sure wether the pistons being out too far is even the problem or what happend and before taking everything apart again, here is a breakdown of what I did.

1. I disconnected the 12v battery before I started, because I didn´t wanna deal with any problems, as it was suggested.
2. The brake caliper came with compressed brake cylinders, so I dind´t bother much with that part.
3. As I had ordered the wrong brake pads (because they were changed after 2004), I had to wait forever, so I thought I could maybe at least start the brake bleeding, using the old brake pads.
4. I followed some online instructions to put the prius into "invalid" mode for that, but I couldn´t get it to work.
I asked several times in the german forum, wether the worst thing that could happen would be that I would have to delete some error codes, because I had read SOMEWHERE, that I might accidentally produce some error only a toyota technician could then delete.
I was assured that yes, as long as I had an obd adapter that allowed me to delete any error codes, I wouldn´t HAVE to deal with the invalid mode.
I know its impossible to bleed the whole system this way, as I wouldn´t be able to bleed the air from the main cylinder and other parts.
I was planning to let just THAT part be done in a repair shop, since I was able to fix everything else.
I just wanted to bleed out at least the air from the back calipers, because I had to replace them.
5. I had a "gravity-bottle-device" in the brake fluid reservoir, that should take care of automatically feeling the bled air.
6. I stopped bleeding after no more bubbles came out.

If you can already see a problem from just my description of the process, please let me know.

After the new brake pads arrived, I finished installing them and went for that test drive, but as I said, I could distinctly hear the grinding coming from the back and fuel consumption was way too high, so I knew something had gone wrong.

Now for my questions:

A) Can someone PLEASE clarify, wether I can ruin anything worse than having to delete a few error codes, if I just wanna rebleed the back wheels without tech stream? Its really hard to find a clear answer on this...
As I said: For the whole bleeding I´ll refer to a toyota service anyways, but in order to not ruin anything else even on my way driving to the shop, I would still like to know how to be able to bleed at least the back calipers, if I need to.
B) Could it be that the pistons came out too far, when using the old worn out brake pads for the bleeding and after pressing the brake pedal for the first time (after reconnecting the 12v battery).
And could that be the problem now, because the new brake pads are a lot bigger of course, so when the brake pistons retract, they are still too far in?
I don´t remember how hard it was to close the brake caliper, after installing the new brake pads, so I can´t tell if that was already the problem then.
I don´t really understand how the pistons know how far to come out, is that elerctronically monitored somehow or is that just based on that first pressure being built up?
C) IF that would be the problem...I have a tool to push/turn back the brake piston. Would that be enough to do that and then use the brakes again, when the car is turned on again, to have the brake pistons then move into the correct position, so the brake pads don´t grind on the brake discs anymore?
I read I shouldn´t open the vent valve to drain the surplus fluid out of the caliper, is that correct?
I am assuming that after pushing back the brake pistons I´d still have to do a little bleeding on the rear calipers, correct?
D) If there is no fault in what I did....What else could be the problem? Because as I said, the whole brake caliper was brand new and I even put some extra silicon grease on the guide bolts to make sure they were moving easily.

I still don´t think its impossible the problem is in the parking brake instead, I´m going to try again tomorrow, if I can simply push them back so far, that the drum brakes don´t even connect anymore when using the parking brake and see if the wheel turns freely then, but I really don´t think they are the cause of the problem.

Because when tightening the two nuts I had in place to keep the brake disc secured when working on the calipers, the wheel barely moved anymore, even with the parking brakes adjusted to be too loose, which makes the brake pads the more likely candidate I think...

Thanks for any input on this, I´m so close to finishing the job, so its very frustrating to be literally stuck again...

 

Unfortunately, the people that could help you with this are few as the North American model does not have disc brakes on the rear. You might be comfortable with the assumption that the bleeding process is somewhat similar to bleeding the rear brakes with shoes, but it is probably too different to be useful.

The only things I can help you with are these:

No, you simply press the brake pedal several times to advance the pistons to touch the pads before bringing the brakes into service. If you forgot to or didn't do this, the worst that will happen is you will get codes (DTCs) related to this. This might disable some parts of the brake system, in which case you just clear the codes to resume the bleeding process, etc.

The park brake is best adjusted with the calliper swung up and the pads removed. You tighten the adjusters so that the hub can no longer be rotated easily by hand, then back off the adjustment screw by ¼ turn. Check the hub rotates easily by hand. You will be okay with a very light wooshing sound as long as you feel very little resistance. (sorry about the subjective description.) You will know you got it right by applying the parking brake and counting the clicks. 4-6 clicks is acceptable if I recall correctly.

If you used new OEM callipers, then the piston return distance and function should not be a problem. The distance that the piston moves is measured in micrometres, so it would be hard to see the distance they retract. You might need to assume they are working unless you are persuaded otherwise.

I hope these couple of things can help and others from NZ/Australia/Japan/Europe/UK can chip in with some more answers.

Alles Gute.

 

Disc brake caliper pistons pass through rubber seals that deform slightly when the piston moves. (These are not the rubber dust boots that you can see, but seals that are concealed from view within the cylinder.)

When you apply the brakes, the piston is pushed out however far it must be so that the pads contact the rotor. Then when you release the brakes, the piston returns, always just by the small fraction of a millimeter that the rubber seal deformed.



(Edit: because of PriusChat breakage in the recent server migration, that above image link can't be made to show here. But you can see it here, or in the older post where it appeared, posted before the migration.)

Drum brakes usually have some form of mechanical adjuster. The brake shoe return springs press the pistons back in when you release the brakes, but the mechanical adjuster limits the return to, again, just a small fraction of a mm from where the shoes were in contact with the drum.

 

Thanks for the clarification. Thats information I can deal with, so it actually IS micrometers....

Unfortunately, that wasn´t the problem either.
Took off the wheels again and removed the brake pads completely and it still didn´t turn freely, even after loosening the parking brake adjustment wheel as far as I could.

I could also still clearly hear some grinding and as far as I´ve understood, I should maybe have a "little" resistance when turning the wheel, but I should probably not HEAR any resistance...

My biggest concern right now is that I messed something up, when I forgot to release the parking brake before trying to remove the brake discs. I used two m8 screws as suggested and assumed the discs where just as stuck as the caliper bolts where, so I applied quite a bit of force, before I realized my error.

Also thanks for the information about the difference between the country models, I also wasn´t completely aware of how different they might be...

I´m also not sure wether I could have ruined anything by possibly using too much force to tighten the lugnuts.
I used 149nm for the back wheels, not sure where I had that misinformation from...

I´m gonna try taking it apart and see if I can visually see anything that caused the issue, as I already ordered the wrong brake pads before, due to not knowing they changed them after 2004, is it possible that something like the inner diameter could also be wrong, even when all the other numbers are correct?

 

Ok, upon further investigation it turns out that the brake discs I had ordered where the only ones with an inner diameter of 167,5 mm, while most of the others (that even listed the inner diameter) had one of 172-173mm. That does seem like quite a lot to me and might already be the cause of the issue.

I´m going to measure the inner diameter of my old brake discs, I could also just try to put them back and see if the problem persists, just trying to avoid any unecessary work and do some "mental car repairs", because I´d have to be working at 0 degrees Celsius outside right now...

 

Yeah, no, thats not it. The brake disc diameter of the old disc seems pretty much identical, they also make the same grinding sound.
I think I need to look into the drum brakes inside and see if I can figure it out.
Made a couple of videos and gonna look at some youtube videos, maybe I´ll find something that clears it up.
Should probably hijack another thread then, because its obviously not a brake bleeding issue.