Brake rotors get too hot

I don't know too much about changing the brakes on a Prius, but I do remember reading somewhere about re-setting the computer and being careful with the pistons. There is a long string in here regarding changing the rotors and breaks, I would search for it. It will answer most of your issues.

 

Have you tried checking the wheels and brakes dynamically? That is: front end up, tires and wheels off, in gear, observe turning and heat build-up. Buy a infrared heat gun and search hot spots. To me it sounds like brake pads are NOT retracting to their normal position. Isn't there also some provision in most braking system for the brake fluid to return to the main reservoir ( master cylinder ) thereby relieving pressure on wheel cylinders?

 

You may know, but you want to be very careful about exposing the system to air. There is a complicated air bleeding procedure that only the dealer can do.

 

With that kind of mileage I would consider a total brake overhaul.

 

Disconnect the neg 12V Bat lead for a few seconds and then reconnect. This will not fix your brake problem.

 

With 330,000 Km, mechanical problems can occur, one almost guaranteed problem is dirt in all the cylinders, including the main. And hoses. No amount of lubrication from the outside will aid the brake cylinder in working and RETURNING to neutral. This was a taxi ! They drive erratically, brake hard, Etc.

 

Your situation sounds very similar to what tommerdoo experienced, so you probably want to follow the details here.

You can learn a lot by putting a hard block in the jaws of the caliper, lightly braking until the piston is stopped by the block, then measuring the piston retraction when you release the brake pressure, as described in that thread and the one linked from it. An old abused caliper may have no retraction at all.

If you see no retraction when applying and releasing the brake, your next step can be to attach a hose to the bleed screw, open it, and push the piston back a little. (This will force some fluid up into your hose. Route the hose upward from the caliper so the fluid stays there. You could get a little more fluid with a part-stroke of the pedal, just for good measure.) Now close the piston on your block again, this time not with the brake pedal, but by applying (low) air pressure gently through your hose. If you play it right, there's enough fluid in the hose that you don't get any air into the caliper by doing this. If you use a clear hose, you can see it.

If the piston has proper retraction when you are air-actuating through the open bleeder, but no retraction when the system is closed, the caliper may be ok and you have a fluid blockage somewhere upstream. If it doesn't retract in this second test either, your caliper needs attention.

It is also possible for certain cheap remanufactured calipers to have no retraction at all, right out of the box! So I've become an advocate of sticking with Toyota's calipers, either new (but they're pricey), or rebuilding them yourself (which is inexpensive).

About $33 will get you Toyota's rebuild kit for both sides (04478-47040, includes all rubber and miscellaneous bits needed including the correct grease, but no pistons, if you need one or both of those they are $18 each).

By the way, since for any pad replacement you need to push the pistons back, I've seen it advocated that you always open the bleeder to do that, so the fluid you are forcing out of the caliper does not get back-forced up through the rest of the system. The advice is probably good. In any case, when you do it that way, you will effectively do a partial fluid change, where you force out about a caliper's worth of the oldest, most heat-exposed fluid in the system, replacing it with some from further up the line, and topping off your reservoir with new.

-Chap

 

Very explicit and interesting post.

 

It happened to my infinity g20. changed brake hoses, calipers, rotors pads and abs pump. Turn out to be brake master cylinder.

 

You are asking exactly the right questions. If you look again at my earlier post, you will see that what I suggested will give you a way to find the answers. If the problem is in the caliper (could be dirt, corrosion, hardened rubber seal, ...), then you will see the same failure to retract both when the bleed screw is closed and you are testing with brake pressure, and also when the bleed screw is open. If the problem is above the caliper, you will see failure to retract with the system closed, but proper retraction with the screw open. Doing that test is the way you can find out which case you have.

Make sense?

When most PriusChatters talk about a brake fluid flush/replacement, it is just a matter of opening the bleeders at the wheels to let old fluid out, while careful to keep the reservoir topped with new. There are a lot of threads here on how to do it, and I also highly recommend your repair manual at techinfo.toyota.com.

I cannot recommend any more "heroic" effort like trying to blast the system out with substances other than brake fluid. I've not heard of anyone doing that, I don't think I would try it myself, I can picture it not going well.

Sure, they're covered in the repair manual and in plenty of threads here. But you are getting ahead of things. You started with a first question: how to get evidence of whether the problem is in the caliper or above the caliper. That's still your first question. There is time to plan what to do about the problem, after you have more evidence of what the problem is.

-Chap

 

You'll probably be helped by reading the thread I linked to earlier, and the one linked from that. (There are some other details covered there that won't matter to you, but the description and photos of a piston retraction test are what you should look for.)

The point of the test is not whether you can push the piston back, but whether the piston pulls itself back when you release the pressure. That is done by the elastic rubber seal and it is necessary to keep your brakes from dragging.

You need to find blocks of some relatively noncompressible material (I used nylon blocks, but whatever is around), roughly as thick as the rotor and the pads, put the blocks between the piston and caliper jaw, apply pressure until the piston just touches the block and stops, then measure the return of the piston when you let the pressure off.

On a good Prius caliper it seems to be about 0.3 mm.

The photos in the earlier thread should help you.

-Chap

 

Some how it lock only the front right when I drive about 4 to 5 miles. It became cherry red I mean cherry red then waited for it to cool down and it would locked and became red for another 4 to 5 miles. The last part I replaced was the master cylinder and it fixed it.

 

Yikes, that was not good!