In general, I would suggest 90% of safety system work should be done by a trained tech.


Brake pads? No Big Deal.
Calipers and in? Get it to your local guy.
Airbags, seat belts, etc? Dealership.

Ukroz pops up in the following thread with some helpful advice: 2007 Highlander rear caliper replacement

If you're comfortable with brakes but don't want to do the bleed (including all the TechStream stuff), hand it off before the repair. Seeing it through start to finish or going to a shop is far better than doing part of it then asking the shop to take over. They can't guarantee a job they didn't complete in their shop.

 

Pinch brake line and replace caliper. Just bench bleed it before you install it, so it will be filled with fluid.

Bench bleed caliper method:





Bench bleed the calipers before installing them: While prepping the new calipers I noticed my MC bench bleeding kit on the bench. The fittings used for the MC will also fit the caliper. I used the fittings/hoses from my MC bench bleeding kit (O'reilley's) plus a huge syringe I found at a grocery store. Connect the syringe with hose to the speed bleeder. Screw in a plastic push-on hose fitting (from a bench bleeding kit) into the inlet of the caliper with a hose to a bottle to catch the fluid. Push fluid into the caliper with the syringe being careful not to push any bubbles in the hose into the caliper. Once the caliper is full, and no bubbles are seen, close the speed bleeder and plug the inlet with a M10 x 1.0 bolt. I was amazed at how much air flowed out of the caliper. It took about three full syringes of fluid to get all of the fine bubbles out. After installing the calipers (see procedure below), and doing one side at a time, it only took three pumps to get a firm pedal for each caliper.


Steps:

• Bench bleed calipers being sure to tighten the speed bleeder and install a M10x1.0 bolt in the caliper inlet when done to keep the caliper sealed.
• Fill MC reservoir with fluid.
• Push brake pedal with your hand and block it in place with a stick between the seat and the pedal. This blocks the fluid return port in the MC so fluid will not flow out of the MC.
• Remove old caliper leaving the flex line attached and hang it from the spring with some wire. This keeps the brake line sealed and prevents any fluid loss while installing the new caliper.
• Install new caliper and pads.
• Move the flex line from the old caliper to the new caliper. Since you blocked the return port in the MC there should be almost no fluid drips from the open flex line.
• Attach hose and catch bottle to the speed bleeder. Open the speed bleeder and pump. The first pump will go to the floor because the piston will move out taking up the slack between the piston and the brake pad/rotor. The second and third pump will firm up the pedal.

 

Excellent detail. Thank you for sharing that. At the final step, once the pedal firms up do we subsequently tighten that speed bleeder and remove the hose? Why is the bleeder open during pumping?

I should also ask: how does holding the brake pedal down keep the MC from returning fluid? Isn't the pedal physically disconnected from the fluid? Also isn't pumping the brakes to get pressure to the caliper the same process as bleeding the brakes manually, risking damage to the system?

In case we feel confident we completed the process well enough should we still drive directly to the dealer for a proper flush?

 

with a bleeding bottle or bag it will only suck in fluid, not air. unless you are sloppy with it. it is designed to be a one person operation, but found it better to still use two people to keep an eye on the operation. As I get older I do not keep up with the latest home garage mechanic tools, so there maybe something newer we can use at home. I always used a box wrench on the bleeder zerk. (why is there a line through my text???)

 

Thank you for your replies, retiredat444. I've ordered replacement calipers. We'll do our best to be careful and not sloppy during the replacement. And hopefully we can find a shop that will doing a brake flush for us without much trouble. I'm finding many shops are geared toward diagnosis -> repair, and have a lot of trouble handling a request for a specific procedure or work to be done.

 

The 2010 Prius has an "invalid mode" that can be accessed without TechStream that allows the rear brakes to be bled in the usual manner. The fronts can be bled normally at any time. A little research might indicate that your HiHy is the same. No special skills required for new calipers. Just be sure to use the new copper washers that come with.

 

Thank you for pointing this out. I did a search and found discussion of Invalid Mode with the Prius and on an Avalon, but haven't seen that it is a feature of the HiHy. I may do the chicken dance and see if I get the same result with the brake light blinking.

 

I have a follow up report on what happened for us during the diy caliper replacement, in case it may be helpful to others. One front caliper was highly suspect as having a problematic piston, evidenced by dramatic pad wear, and the wheel not spinning freely after letting up on the brake. We were not confident about the "invalid mode" approach mentioned earlier in this thread, so we followed the bench bleed instructions. It was not without incident.

The new calipers were bench bled as per the bench bleed instructions above, using a syringe and the MC bleed kit. Very straightforward. The old caliper was removed from the rotor without disconnecting it from the brake hose, and rested conveniently nearby. Next, the brake pedal was depressed to "block the return port" on the MC to help prevent any introduction of air into the system. Unfortunately this step immediately engaged the master cylinder, which meant brake fluid was now being continuously pumped to the suspected faulty caliper still connected to the system but no longer in place on the rotor. Without the resistance provided on the rotor, the pressure/fluid blew the faulty piston completely out of the caliper and the MC kept pumping fluid. Quite the mess.

So the step where the brake pedal is held in a depressed position is one we question. Even if the piston had held, wouldn't the transfer of the brake hose from old to new caliper result in pressure loss and re-engagement of the MC with similar fluid loss results? Not sure what we missed in following the directions in this process, but if there is a way to clarify the instructions it could be helpful for other hopeful diy-ers in the future.