Brake Actuator Replacement

You may have read my previous post about a failing brake actuator. Shortly after purchasing our 2008 in February of this year, we started hearing the infamous "barking" when we were stopped with the brake pedal applied. It has slowly degraded to the point where it was really driving us crazy. I used Techstream about a month ago to replace the fluid that had been replaced a year or so before at the dealership. It seemed a little better, but not much. In the past week and a half, it got noticeably worse. Not only did it bark when stopped, but in that last 5-7 mph where the friction brakes take over, it would bark, and you could feel a surge, or rather a slight release, in braking when it did. It only did that for a couple of days before all 3 brake lights came on.

I sourced a used part near me from car-part.com (search for ABS pump). I found a grade A pump for $135 after core exchange. I tried to take pictures of the process, but I get really hyper focused when I am doing this work and only got a few bad pictures at the beginning. I'll instead describe all of the basic tasks I had to perform, tools required, and things that I had to figure out. If you have any questions, don't hesitate to ask.

Required:
Techstream (miniVCI) This is a must. The procedures for bleeding the brakes make this an absolute requirement. It also assists in making sure you have fully released the accumulator pressure.

Subscription to alldatadiy or toyota Techdata. I subscribed to alldatadiy as they supposedly have the same manuals, but instead of $20.00/day you can opt for a one year for $28 or 4 or 5 years for around $50.
Alldatadiy provided me everything I needed to know, and even had each step you needed to perform with Techstream, and which system, menu you needed to use to get there.

14 mm socket to remove wipers
12 mm socket (1/4 inch)
10 mm socket (1/4 inch)
6 inch ratchet extension (1/4 inch)
1/4 inch ratchet
10 mm box/open end wrench
10 mm flare nut wrench (for hydraulic lines)
8 mm box/open end wrench
Torx T30 (for one bolt on the inverter cover)
needle nose pliers
offset long nose pliers
trim panel removal tool
multimeter
large container and 1/4 inch flexible line for brake bleeding
1/4 inch flexible tubing to bleed the inverter loopd
22 mm (I think) socket to remove inverter drain
a lot of shop towels

I first started by removing the wiper assemblies and the cowling below. Study carefully how the cowling is attached. It clips under the bottom of the windshield, and then there are just tabs that slit in below to lock it in place along with one pressure clip on each end. After removing the wiper motor, you remove the cowling that it's attached to by removing the 7 10 mm bolts from it, and removing the relay housing on the front of it, 2 10 mm bolts).

Note: As you follow the manual, it will have you go to the steps for removing the inverter prior to initiating the next step. You will want the inverter and power connected so you can turn the vehicle on and bleed down the accumulator pressure. Then you can proceed to removing the power/inverter.

I bled down the accumulator using Techstream. I know others have done it by removing no 1 and no 2 brake relays from the engine compartment relay bank and then depressing the brake pedal 30 or so times until there is absolutely no pressure left.

I disconnected the auxillary battery and removed the safety plug on the HV battery pack.

I removed the coolant drain plug on the transmission, as well as the cap for the reservoir to allow all the coolant to drain out of the inverter. I removed the inverter cover and using my multimeter as instructed in the manual, checked for any voltage across the terminals of MG1 (connection close to the firewall), and the terminals of MG2 (at the front). After doing so, I removed all of the connections for it. I sure wish Toyota licensed the weather pac connectors that GM uses. They are very clear how they are locked in place, and very easy to remove. Many clips in this process use different methods of security them. Most are just a single button you push down, and then pull, but then others have an usual latching mechanism. The "circuit breaker" located just outside the inverter on the drivers side requires you to push on the back of the fitting. It will slide in and then allow the whole connector to pull back. Also be aware when you need to remove a wire attachment point. On most cars, they are friction fit and can be removed with a trim panel tool. On the Prius, from the opposite side you use either needle nose pliers, or offset long nose pliers to squeeze it from both sides which will release it and you can pull out the connector.

With the inverter out, the first step the manual says for continuing on is to remove the brake fluid. I couldn't find anywhere in the manual, nor online, a specific procedure for doing so. I removed the front left tire and using a suction brake bleeder, pulled all the fluid out of the reservoir and that circuit of the system until I pulled only air. Unfortunately, there is still a lot of fluid left - particularly in the fluid return line from the actuator to the bottom of the reservoir. In hindsight, I should have at least performed the same procedure on the passenger side front.

You will remove a lot of various hydraulic fittings that attach both at the actuator and other fittings. Look carefully as you disconnect to find out where they are physically supported in the middle. You will want to make sure all attachment points are disconnected so the lines can be removed without distorting them. Every line I disconnected had a little fluid in it, so I would place a disposable shop towel to catch the fluid. You will disconnect the auxiliary water pump for the cabin heat. Do not disconnect it's water hoses, just the physical mount. If you remove the bracket from the pump, you will be able to remove the actuator from underneath the lines (just barely enough room). Make sure you clean up any brake fluid spills as it is an excellent paint remover. It will also damage rubber hoses so watch out for spills on cooling lines, the power steering bellows, and CV joints.

The actuator comes out as a large unit with a very large "A" shaped bracket attached to it. You will need to remove this, the large vibration reducing weight at the bottom, and any other brackets that are attached as they likely will not come with the replacement pump. Take pictures after you pull it out so you can see how all these things attach.

Reinstalling went very well for me. It is truly the reverse sequence with a few exceptions. I hooked up all the hydraulic fittings and return line so I could fill the reservoir with fluid. I found that if patient, much of the air returned back to the reservoir and drained it down. I have what turns out to be an extremely helpful tool - an air assisted bleeder from Harbor Freight. It comes with a bottle that goes over the brake reservoir to keep it topped up. It worked extremely well and I never had to worry about pulling air back into the system. I performed the step of bleeding the master cylinder before I put the inverter back in as clearance is much tighter. The manual state that you simply remove one fitting on the master cylinder, then another just to the side of it. Plug those holes with your fingers and have the brake pedal pressed and released. I didn't know what to expect. Your fingers are there to prevent any air from getting sucked back into the master cylinder, however you will have to allow fluid/air to come out, so place a few shop towels beneath this as you perform this process. I made sure to leave my fingers in place for a few seconds after the pedal was released to make sure no air made it's way back into the master cylinder.

After putting the inverter back on, and reconnecting all it's connections (electrical and fluid), you can put the cover back on. I refilled it with new fluid and after the level stopped dropping, I reconnected the auxiliary battery and the HV battery disconnect (remember to push it in, fold the handle, and then press it down). I connected the Techstream, and pressed start to get to ready. I had brake errors because you leave the relays out until part way through the bleeding process. The engine started and when stopped, I turned my attention to bleeding the inverter loop. The pump was running, and though it didn't sound like there was any air in it, I had no circulation. I loosened the bleeder until fluid came out, but it still wasn't circulating. I attached tubing to the bleeder and opened it wide. I was amazed how long it took pumping air filled fluid through this line before all the air was removed and operating as normal. I know some people have success without using the bleeder much, but for me, it took 5 minutes or more of having this line open before all the air was removed.

I then proceeded to bleed the brakes. As stated in the beginning, you must possess Techstream (minivci) to perform this as there are many functions where it cycles valves inside, pressurizes and then released the accumulator many times, and other such things in order to get all the air out. When in the ABS subsystem, and under the utilities option, select air bleeding and then select removed brake actuator. You will begin with the relays removed bleeding the FR and then the FL in the traditional manner with someone assisting you at the pedal. It took quite a long time before I had clear fluid with no air. After this, the Techstream will advise you to shutdown, install the relays, and power back up. This is where you will find a lot of procedures such as "pressing and releasing the brake pedal 30 times in 30 seconds" or "20 times in 20 seconds". It will also cycle the accumulator 5 times after which you have to shut off and power back on to reset after each. Note that many of the procedures seem to place you back at an earlier stage in the process, or have you repeat things after you think you have done them. I believe it had me perform a bleed on the FL 5 total times. After these steps you will get to the rear which are very easy. With the relays in place, the pedal will be depressed and held. The bleeder will be opened and the pump will provide continuous pressure. Make sure you get all the air out, but I suggest doing it slowly. If you open the line wide open, you can reduce the brake pressure until the system goes into alarm mode after which you will have to shut off and back on to reset. Also, make sure you keep a careful eye on the level in the reservoir.

After all was said and done, I had used a full 32 ounces of fluid to refill and bleed the system. In fact, it was just enough to leave the level 2/3 of the way towards the maximum line. You may need more if you have difficulty getting trapped air out. I also had issues with my particular adapter disconnecting partway through the process. I would just start over, and skip over what were just instructions to get me back to where I was. Therefore, I suggest you pay close attention to what you've done and where you are to make sure you get back to where you were - keeping in mind that some tasks are intentionally repeated, so don't let that throw you.

One thing that I was very happy about is that nearly every single 10mm and 12mm bolt that you have to remove are easily accessed with a 6 inch extension on a 1/4 ratchet. I was continually amazed that it always seemed to be the correct distance to clear things enough to enable ratchet movement. Do yourself a big favor and get one if you don't have it. Otherwise, you will be frustrated trying to access various bolts. Also, possess a flare nut wrench. Many of the hydraulic lines are quite tight. If you use a standard open ended wrench, you may round it off.

I am more than pleased with the results. It took me a little more than 5 hours total to perform the work. I could probably do it in 3 now, not having to figure out how connectors come apart, and knowing the order in which to do certain steps.

My parting advice if you have to do this is to make sure you have Techstream, and subscribe to alldatadiy and read and reread all the steps listed there.