Brake actuator replacement in pictures

Hi Galaxee,

Thanks for providing the photos and the steps behind that job. Truly fascinating.

Yesterday, having the cowl off my 2004 to do some routine maintenance, I was nosing around that area. I took a couple of photos on the passenger side of the cowl focusing on brake parts, and wanted to ask for your (or your DH's) comments.

The first photo is of the brake stroke simulator, I believe. Can you confirm?

The second photo seems to be some kind of horn but I can't find it in the repair manual. That is located below the brake stroke simulator. Is that the horn that provides warning when the brake system has a serious problem?

Thanks!

 

Hmmm only slightly less complicated than building your own nuclear bomb. I'm sure he had fun with that job

 

Wow, great stuff! I have some additional pix of the actuator
and its relationship to the inverter in my maint50k page
and managed to avoid dropping the inverter too heavily onto the brake
lines during all that, but have never actually cracked any of the
coolant lines for that process or cleaning the throttle body. Never
had the inverter completely out of my car, obviously.
.
What's with the "resistor pack", what does it do? I think I've seen
it up under the dash [left side next to the sidewall, right?] but
never really knew what subsystem it was for. You didn't change the
brake ECU during this, correct?
.
How many hands/fingers at once did it take to perform the initial
bleeding? The manual implies that it takes at least two people to
start the process and get the rest of the lines hooked up, before
the scantool stuff even begins.
.
The brake beeper is definitely inside, mounted right on the ECU,
visible in this pic from the wheel-speed-diff page next to all the
metal spikes that form the brake-ECU heatsink. [Why heatsinked?
Because all the solenoid drivers for the actuator are in the ECU.]
Pulling the two pump relays and playing with the pedal is a good
way to make it start howling, if anyone's curious to mess with it.
.
_H*

 

I looked in the repair manual, and this says: "Be sure to replace the actuator and the resistor together. If they are not replaced together, motor noise may be increased."


However the 2004 wiring diagram manual, Brake Control System section, does not show the resistor assembly so it is very strange.

Also, to remove that resistor it looks like the instrument panel has to be disassembled to the point where the passenger airbag can be removed, so it seems that part of the repair is not a minor effort.

 

Psst, 2006 manual here. Keep it quiet. (Despite the EU URL, this is the North America manual.) Either there wasn't a resistor there on the 2004-2006 car, or they didn't think it was going to need replacement and didn't mention it. It could be that the resistor has to be a specific value to perform whatever task is necessary (motor speed control?) and the motors are actually varied enough in winding resistance that they can't use the same resistance on all cars.

I wouldn't be surprised if the complaint that the motor was too noisy was 'fixed' by adding resistance to reduce the voltage across the motor, making it spin slower.

I'd guess that the resistor is in that odd place so it's in the cabin air flow. It looks like it dissipates quite a lot of power.

 

Hi Galaxee,

I've attached two pages from the 2004 EWD that seem to correspond to the fuzzy screenshot in your post #11. Note that in the 2004 diagram, a 30A ABS fuse (F17 fuse holder) is shown instead of the resistor. Does that fuse appear somewhere else in the 2006 wiring diagram?

The green wire receives switched power from the ABS MTR relay, which receives 12V power via the 30A ABS-1 fuse. It is very strange that there are two 30A fuses inline in that circuit.

If all that the resistor does is reduce current flow to the motor, then it seems strange that it is necessary to match a particular resistor value to a given brake actuator.

Perhaps that resistor was added as an engineering change just prior to production start, so the 2004 repair manual was updated but the wiring diagram was left alone.

 

Our brake twerping sounds have been with us since 25K. It is now at 30k. We took our 07 in this week [2-2-2010]. The dealer said the squawking noise was due to air in the brake line. The dealer bled the brake lines and replaced with 4 pts of brake fluid. So far, the noise is gone. Are we going to be weary of an actual brake actuator failure in the future? That $2322 repair job is scary. Another advice we need: should we buy the xt-warranty for $----, with the possibility of the actuator failing or do you think it was just as the dealer stated: leak/air in the brake line, fixed! ?

 

My 2004 "bark" was fixed by bleeding the right front brake in December 2007. No return of bark yet (about 60k miles since the bleed). Have faith.

JeffD

 

Thanks for all this information and pictures. Amazing people at PC! My 2010 has the same barking problem. Bleeding was only a temporary fix. The actuator will probably be replaced tomorrow, if the Toyota rep agrees. Man it is a big job!

 

galaxee & patrick wong,

I posted at the begining of last year with my BRAKE, (!), VSC, & ABS lights illuminated. At that point (thanks to you investigative sluething by patrick) I managed to diasgnose the problem as a Relay issue.

Unfortunately, these same warning lights came on, and after checking relays, I gave the 'ol prius to a shop to diagnose. As I dreaded, it turns out the brake acutator is not holding pressure -- indicating an internal leak.

My question is threefold:

1) Is there any special trick to de-pressure the braking system? I understand that brake lines are generally very high-pressure systems. I noted that you removed the "non-pressure hose" first, but do not make any mention of the rest of the hoses.
2) There is no final agreement in this thread about whether or not the resistor pack MUST be replaced. Does any diligent home mechanic happen to have a part # to refer to? I was not able to find it at Toyota Parts - Genuine OEM Toyota Auto Parts and Accessories -- unless is called "DAMPER, BRAKE ACTUATOR" part # 44599-47010
3) Lastly, I am looking at salvage parts and finding two differnt part #'s for the brake actuator. The parts all seem to list part # 44510-47050, but when i search that on toyotapartszone, I can only find part # 44500-47090. do all the 2004-2009 Prius use the same part? Or, does the 04-05 model differ from the 06-09?

Answers to any of these questions would be wonderful! (most importantly my question about de-pressuring the brake system).

Thank you,

Connor

 

Hi Connor,

Galaxee does not monitor PC as much as in the past so she may not respond to you.

Regarding depressurizing the system, I suggest you disconnect the 12V battery negative cable where it bolts to the body, then depress the brake pedal a few times. That might work.

The resistor pack does not have to be replaced if you can tolerate more noise produced by the system.

You'll have to figure out the part numbering on your own, perhaps toyodiy.com might help.

Please note her warning that this job is not for the home DIYer especially if you do not have access to Techstream. If you persist, then I strongly suggest you obtain repair manual info from techinfo.toyota.com so that you will have the full procedure and associated safety warnings available to you.

 

Guys thanks for all the information. I've read several of the forums over the brake actuator. I understand that this shouldn't be attempted at home but KBB tells me the car isn't worth me getting the work done. I have found a salvage part, got the mini VCI, and will be buying the 48 hour on TIS. Before I take the plunge has anyone done this? And any last advise. I use this car for delivering newspapers and I'll run it into the ground. Plus I find this good experience because I want start school for automotive tech in the fall.

 

There is nothing wrong with you doing the work at home if you obtain the factory repair manual info, have Mini VCI which emulates Toyota Techstream, and the correct tool to remove the brake lines from the actuator (a six point box wrench of the proper size with a slit to allow you to get past the brake line, onto the hex fitting) without causing damage to the brake line fittings.