New Rear Shoes REAL tight?

You didn't step on the brake pedal during any of this did you?

Usually its because its all rusted up in there and the star wheel although turning is not moving the pad. Take it back off and lubricate everything and set star wheel to 0 and use star wheel while drum off and check its all working.
While drum off set star wheel for pads all the way in. Put drum back on and starwheel till they hit and rub on drum a little. Check how many turns it takes starwheel to so this. You may need new drums.

 

If you cleaned up everything like Ed suggested and you are sure the star wheel is adjusted all the way in, it sounds to me like the material on the brake shoes is just too thick! You mentioned they are aftermarket. You might go down to the Toyota parts dept. and look at the shoes they sell. If you see a difference in the thickness of the material, then you will know that is the problem. Also, the aftermarket shoes might not be the correct size, or arc to begin with. Check this by comparing the old one's to the one's you put on the car.

I am assuming (hate to do that...) you disconnected the battery before you did anything to the brakes. And that at no time you have stepped on the brake pedal once you pulled the drums.

Ron

 

The Prius brake system is like no other car you have worked on. It may look the same, "it is not".

When working on the brakes it is very important to at minimum disconnect the 12v battery.

Have you ever notice that when you open the drivers door on occasions you hear an electric pump run, this is the pressure pump for the brake system and it can run at any time to top up brake pressure. If it does this with the rear drums off it can pop a cylinder piston out.

The system cannot be bled by normal means so do not try or even undo the bleed nipple. For your immediate problem do both pistons in the brake cylinder move or is one seized. If both are free the likely thing is that the brake linings are to thick. One other possibility is that the emergency brake cable has been adjusted to tight.

John (Britprius)

 

I would double check the adjusting fork is in the slot of the rear brakes, then push the two brake shoes together with my hands to try to compress any slack. Hobbit has some interesting stuff on the adjusting part of the brakes here.
Self-adjusters

Since no warning lights are on, I'm guessing the brake system is still functional.

 

If what you have just said is correct I'm not sure it is. The air cannot be bled out in the normal manor on the Prius.

John (Britprius)

 

The Prius uses a positive pressure system and unless ECU sees this pressure it will throw a fault code. This usually causes wheel lockup when coming to a standstill. Bleeding has to be done with a devise such as Toyota Techstream to operate all the valves in the system. See hydraulic circuit below.

John (Briprius)

 

I do agree with John. I suggest you take your car to Toyota. Have them bleed the brakes properly with the TechStream software. Also pay them to check the system properly. The Prius brakes are unlike any other "normal" vehicle out there as John and other's have pointed out. It would be a very good idea if you informed them of the work you have done.

Consider this, your brakes are a safety system. If they are not functioning properly, you may find yourself in a situation which could cause a collision and or death. I am not trying to scare you. I am simply pointing out that you could be overlooking something that may cause catastrophic conditions further down the road.

Ron

 

I am not just being over cautious with what I have explained.

The Prius normally uses regen braking (electrical) but it also has vehicle stability control "in other words the car can apply braking to a single wheel or any combination of wheels without you touching the brake pedal".

It does this if the ECU's sense that the car is not responding to steering input as the ECU's predict would be the norm applying individual brakes as required to put the car back on course. Any air in the system can have serious consequences.

John (Britprius)

 

Oh boy. I guess since I was the first responder I should have warned him and expounded on my "you didn't step on the brake pedal did you? " post.

He's in it now.

 

John,

I just replaced the rear shoes on my 2004 prius and accidentally let the left cylinder piston pop out.
I put everything back together, bled the system using the standard bleed nipple and took the car for a test drive. No warning lights, no pulling in an emergency stop, putting the car in neutral with the foot brake engaged the car is impossible to move.

On the surface all appears to be OK. What I don't understand, is that if there is a pump as shown in your diagram, why the system would not pump itself back up to the maintained pressure. It strikes me that to have a sophisticated system such as this one that is not self correcting would make the car deadly as soon as a seal got even the slightest leak as the pressure pump would simply push out the brake fluid.

Furthermore, knowing that there are many many DIYers out there, why would Toyota put a standard bleed nipple on the back of a system that required "special" treatment. It would make much more sense to put some other fitting that was custom such that only a dealer could make the repair.

Just my two cents

 

Any brake system on any car using hydraulic brakes will have brake failure if the seals blow and fluid leaks out. The Prius is little different in that respect. Toyota would also assume that anyone working on the brake system would first read the manual and have all the required tools to hand listed in the manual..

However the Prius does monitor the line pressures at 7 different points (see diagram for pressure sensors) then gives both visual and audible warning of serious problems, ignoring this brings you and everyone around you into peril, and that is only the start of the story.

It has a split system so that pressure loss in part of the system does not not affect the whole system and if the accumulator pressure is lost the brake pedal still works but at higher pedal pressure.

Apart from regen braking that will give you normal braking down to 7mph without using hydraulics.

Under normal driving above 7mph all the fluid lines are turned off to the wheel cylinders and regen (electrical) braking is used on the front wheels only (no rear wheel braking). If the braking effort required is to great for the regen system, or one of the front wheels begins to loose grip the car transitions to hydraulic brakes in a controlled manner.

Loss of electrical supply will give hydraulic braking by default The brakes are then able to reduce pressure to any wheel that may be starting to lock and re apply pressure when the wheel speed matches that of the others "ABS"

Now add the complication of stability control by braking individual wheels with no input from the driver it should become apparent why the bleeding of the brakes by being able to control all of the valves in the brake system to remove air in that part of the system is critical to the correct operation.

John (Britprius)

 

I should have added that the fluid container is although topped up from one cap is three independent reservoirs, emptying any one does not empty the other two.

John (Britprius)