Very faint clicks at stop from brake actuator

Yes, probably means Apply, I just automatically thought it was Accumulator since its pressure source

Definitely make sense

Thanks

 

Update:

Actuator + Accumulator/Pump came in, installed and bled. Car brakes perfect.

• Pump comes on a lot less frequent and much shorter duration.
• No more clicks : faint one and the louder one felt on entire length of all 4 brake lines.

Will separately post all the challenges on install and cheap MVCI techstream setup.

 

Follow up with a graph of working actuator behavior after replacement.

Car in IG-ON mode (press power button 2x without foot on brake) Followed by foot on brake. Compare with failed actuator/accumulator in post #18



Note the following

• SLR is 0A entire time. Seem to make sense, no need to release any pressure feeding the downstream ABS.
• SLA does pulse every 3-4s gradually extending this time. Probably just feedback loop to converge on target pressure.
• All other solenoids are steady.

Compared with failed part, very different picture (SLR going crazy)

Accumulator + pump

• Runs much shorter period in all scenarios. Opening door (after a couple of hours) only produce 1-2s of pump run time. With the internally leaking actuator/accumulator combo, it would run 5-10s after opening the door.
• The pump also seems to run less frequent. Accumulator sensor (pressure sensor voltage) shows a much slower drop (seems both using and not pressing brakes, didn't study carefully) indicating no more internal pressure leak somewhere in the circuit.

 

Actuator Repair

Was curious why no one repairs these failed units (Simpler ABS units usually have mail in order repair services and issue seems to be always on the electromagnetic side of the solenoids). Searched and found secondary used Prius markets where labor is cheap (Pakistan, India, I also heard Mongolia is a huge 2nd hand Prius market imported from Japan) and they do have repair services for these.

Here is a video (several exist) that shows how to remove the electronics and coil side of the actuator (on 1 board) and presumably send it in for repair.

Removed mine and looks like this



"If" this is the common failure, then its not the mechanical hydraulic channels and actuator valves that fail. Rather, its the electromagnetic side of the actuator and/or likely the electronics power stages. On/off solenoids probably have relays and linear solenoids probably have power transistor/switches and PWM pulsed for desired current (and resulting position) level. All are possible failure points handling higher voltage, current, and heat.

To remove the board from that assembly require desoldering a lot of header/connector solder junctions. Will post back after getting that done with a friend's Hakko desoldering tool

Accumulator Pump Repair

Also saw a few videos on these and also from secondary used Prius markets. Failure point is the motor bearing. Coincidentally my new accumulator motor is quieter than the one removed. Presumably original 150k mile one with lots of brake use (short trips, hilly region) has some rotor shaft bearing wear.

 

No business for me. Just curiosity Others are welcomed to pursue. I guess tons of these getting thrown away.

 

Thanks for the repair attempt history. Indeed 3rd world parts from Japan in local currency aren't going to be much lower than US and probably outweigh monthly salary along with low liability.

Shipping entire brake actuator both way would also add quite a bit of cost and eat into just new from Toyota on sale. Mine was $900 total shipped ($457.47 actuator, $446.32 pump+accumulator) Would be been another few % cheaper if had 25% rather than 20% Toyota online parts sale.

And as you noted, great deal more complexity than typical ABS, ECU, TCM modules that have many online repair options. Most are often electronic in nature and frequently failed solder joints (especially early 2000 era beginning of lead free solder formulation)