My brake actuator replacement

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by JasonATX, Mar 18, 2019.

  1. JasonATX

    JasonATX Junior Member

    Joined:
    Mar 22, 2013
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    2007 Prius
    Model:
    II
    Hi all!

    Replaced my brake actuator this weekend and figured I'd give a short write-up in hopes it might provide some useful data to others in the future.

    First, I wouldn't have even attempted this without all the information already posted on Priuschat, so a big thank you to all those that post here.

    The threads and videos I reviewed to prepare were numerous, but these were the ones that helped the most:
    Brake Actuator Replacement | PriusChat <- Main thread source I used
    I replaced my Brake actuator | PriusChat
    Brake actuator replacement in pictures | PriusChat
    https://priuschat.com/attachments/changing-the-gen-ii-prius-actuator-pdf.32931/



    I also got copies of the sections of the Toyota repair manuals for the following:
    Inverter removal/replacement
    Brake actuator removal/replacement
    Brake bleed procedure

    I used Techstream with a VXDIAG to communicate with the car. I have MiniVCI as well, but upgraded to a VXDIAG a while back as the MiniVCI had a tendency to error out/disconnect randomly. VXDIAG has been stable.

    My vehicle is a 2007, currently with 235k miles. Back in mid 2017 (~210k) I noticed the actuator would run about once a minute, even if I was sitting still or cruising at highway speeds. Techstream showed a steady loss of pressure in the unit over that minute. I started keeping notes on how often and how long the pump would run, secretly hoping it would fail in time for the extended service campaign replacement offer that expired end of 2017.

    However it didn't fail, but continued to degrade slowly over time. The amount of time between actuator runs when idle slowly but steadily dropped over time. Around July of last year (2018) it got down to about 25 seconds in between activations when idle. I then started looking for a good quality used part online. I still had some time so I wanted to be picky on which used part I got. After a few weeks of watching, a freshly wrecked 2009 with ~100k miles got listed for parts on one of the sites I was watching. Being the last compatible model year, relatively low mileage, and wrecked due to a rear side impact (site posts pictures of the cars) meant the actuator was probably one of the better ones I could get. Called them up the next day after they listed it and bought it. They said they had already had a couple of calls about it already. Unit arrived and they did a good job putting plastic stoppers in all the holes to prevent contamination. I set the replacement unit aside.

    Over this last winter I noticed that the cold weather making the brake fluid a bit thicker caused the actuator to get a little better, however when it started warming up last month it got to where it would run once every 10 seconds. Still not throwing codes but I didn't want to push it any further so set aside time this weekend to fix.

    The threads I listed above (especially the DrDoug one) and the Toyota manuals made the replacement about as easy as it could be. At no point during the process did I ever feel lost of unsure what next step to take and everything went smoothly. I did go very very slowly, double and triple checking everything. It took about 9 hours spread over 3 days to complete, but in the end it worked great, the new-ish actuator holds pressure at idle for at least 10 minutes (I gave up watching after then). It's also much much quieter than the old one and runs in shorter spurts. If I had to do it again, I think I could get it down to ~4 or 5 hours.

    Here are some of my tips:
    Bungee cords are your friend. I used them to hold the multitude of electrical connectors, brake lines, etc. out of the way while I worked to remove other parts. Was also invaluable in helping me position everything out of the way while I pulled the old actuator out and put the new one in.

    There's a bracket on the left side of the actuator that's not easy to see, but you need to remove it to get the unit out. It's the only nut you'll actually need to come from the left side of the actuator to get to. I got everything else unhooked and couldn't get the old unit out until I found that bracket.

    The Toyota manual has you remove some of the metal brake lines at both ends and take them entirely out. I did not have to do that, just disconnecting them from the actuator and bungee tying them out of the way gave me enough room to do what I needed. I still had to stop every few inches during the final removal and slightly adjust some of the lines so they didn't catch. There is barely enough room, but you can get it out.

    Getting the new unit back in and bolted up wasn't difficult other than it being heavy. The big metal weight on the bottom can get stuck. If it does pull the unit out and try a slightly different angle. If you get it just right it should slide in and to the left. I got the left bracket hole on the bolt first, then the right and bottom.

    The Toyota manual also asks you to remove the Air Conditioner inverter connector. It's the big orange plug I think close to the front left of the inverter. I messed with that thing for 30 minutes trying to get it disconnected but could never figure out the trick. I got the lock slid up but the plug just wouldn't pull apart. Not sure if I just didn't have the right technique or if it was melted together. Regardless, I finally realized that since I just needed to move the inverter out of the way to the left, the connector cord was long enough to support that and I ended up not even needing to disconnect it.

    Speaking of electrical connectors, I think I had more frustrations with trying to get some of those apart than anything else I encountered. My poor fingers were sore from pushing in on those clips.

    The MG1 power cable on the inverter (the orange one in the front that comes up from the bottom), has little rubber tabs you may need to push in with a screwdriver to get it to pull out the bottom. If you disconnect the 5 screws holding the plug in and it seems loose but won't come out, look down inside from the top on the left and right side of the plug and see if those little tabs are catching.

    The three non-orange electrical connections in the back of the inverter were really hard to get to click into place. They slid on easily enough but I had to put a lot of pressure on at least one of them to get it to click into place so it wouldn't slide off later. I've read other threads on here where people had issues with loose inverter connections after everything and I wonder if this is why. Give the connectors a wiggle and a pull to make sure they are secure.

    Take pictures of everything as you go. I also used a wax pencil to mark letters on the electrical connectors and plugs they go into as well as the coolant hoses. Wax pencil markings rubbed off the brake lines too easily so I just put different colored twist ties on those before removing and took a photo. Regardless, everything mostly lines to up where it needs to go.

    Inverter coolant refill went as expected. Use the bleeder valve to let air out and I also squeeze and shake the coolant hoses to help pump the fluid around to jump start the process. About the time you're ready to give up, the coolant starts to dribble out of the bleeder valve.

    For brake bleed, I put the car up on 4 jack stands and removed the tires. I used a cheap Harbor Freight manual vacuum brake bleeder to suck out the fluid from the front right and front left tires (take the cap off the brake fluid reservoir first). I did not try to pull fluid out of the rear tires. I also did the brake master cylinder bleed procedure while the inverter was still out and power disconnected. Not sure if I really needed to, but it didn't take long and it's easy to access the master cylinder while the inverter is out (it's to the far right of the actuator).

    The techstream walks you through the bleed process and it's pretty straightforward, especially if you've read the other threads and the toyota repair manual section ahead of time. You do repeat a lot of the steps over and over, but it does eventually end. I'd estimate 30 to 40 minutes from start to finish. You must have a helper to work the brake pedal while you do other things. The Techstream instructions were slightly different than what the repair manual shows but I think the repair manual may have been referencing a different tool. Just make sure to select the option that says you removed the brake actuator when you kick off the process.

    The only brake bleeding step that somewhat confused me was about in the middle where it has you bleed the front driver's side tire for the Xth time, but this time it's going to have the actuator pump run as well. It tells you to hold the brake down, open the bleeder valve and let the actuator pump run until fluid no longer flows, then close the bleeder valve. Well, if you wait a few seconds after the fluid stops flowing the pump kicks on again and pumps more fluid, so initially I thought maybe you were supposed to wait until it quit totally, but after about the 10th cycle I figured out it meant to stop after that first pause.

    Don't forget to keep an eye on your brake fluid reservoir level and keep it topped it off. I was collecting the expelled fluid in a small container that came with the brake bleeder tool so when it got close to being full, I got to a stopping point and poured it back in the reservoir.

    Buy a bag of shop rags and stick them under anything that might leak brake fluid. Despite your best attempts that stuff will still get everywhere. Make sure to clean up any that touches paint very quickly with a bit of soapy water.

    Keep all the screws/bolts in little plastic bags and label them with what part they came off of.

    That's about it. After the Techstream said it was done with the bleed, I went into the ABS portion of the software and cleared the two codes there (accumulator pressure low and one about a pump failure I think), powered the car down and started it back up to "ready" mode. No codes and no dash warning lights. Put it all back together and drove it around the block a few times to check everything out.

    Anyway, hope some of this helps those that are brave enough to try. Again, it's a looong process, but each step isn't very difficult by itself.
     
  2. Dxta

    Dxta Senior Member

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    Nice job! But you didn't state how you did bled the rear electric brakes.
     
  3. JasonATX

    JasonATX Junior Member

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    The Techstream walks you through the rear bleed procedure. It's the simplest of the bunch, just have someone push on the brake to activate the pump while you open the bleeder screw and let it run until the air all comes out. Techstream walks you through it.

    What I didn't do, is manually pump out the old brake fluid from the two rear lines before starting the main Techstream bleeing program. I did pump out the old fluid from both the front brakes (since that also empties out the brake reservoir) before starting the Techstream brake bleed program.
     
    SFO likes this.
  4. John H

    John H Senior Member

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    Jason, I am about to take the same path of replacing the brake actuator on a 2007.

    Where did you source a replacement actuator ? A couple of salvage yards have prius but not sure how to determine if they have the fixed actuators or the original.

    Also, any chance your original actuator could be rebuilt/refurbished ?

    John (ATX)
     
    #4 John H, Aug 6, 2019
    Last edited: Aug 6, 2019
  5. oldshadetrEE

    oldshadetrEE Junior Member

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    Vehicle:
    2007 Prius
    Model:
    Three Touring
    Jason/John, Didn't see a response to the source for an actuator. What did you do?

    Jason - I wouldn't recommend putting fluid you bled out of the system back in the reservoir. Use new fluid.
     
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