Today I replaced my front(4piston) and rear(single) pads. The rear brakes dont seem like they're working right though. With the car on jacks, foot on the brakes, the rear wheels turn easily.

Both pistons retracted fine, when I put the new pads in.

Could I need a piston rebuild kit for both calipers or could it be something else?

I bled the system with no problems and the pads are hawk hps.

Any input? thx.

 

How about a little more information? Is the 4-piston system a retrofit or an original configuration? If a retrofit, did you also replace the rear calipers with the ones that match the front 4-piston calipers? When you rotated the rear caliper pistons back into the bores did you align the "V-shaped" notches on the pistons as instructed in the manual before installing the new pads.?

Almost sounds like a master cylinder, proportioning valve or brake line obstruction problem. But if you got a good flow of fluid when you bled the rear brakes that seems unlikely. Have you messed with the master cylinder or proportioning valves at all?

 

check the master and slave cylinders and maybe the booster.

 

I read a similar problem in Classic Motorsports magazine but the reader had a proplem with the rears not bleeding. One the magazine pointed to was the proportioning valve which adjust the brake bias during nose dives. When the car is up on a lift or jacks the rear suspension is all the extended and the proportioning valve is going to react differently. You can try to bleed the brakes on the ground or you can jack up the car on the rear suspension and press the brakes to see if the wheels will turn. Do this and see what kind of results you get. Bleed the rears again to make sure you did not get air in there by sucking it in on the caliper side or by running low on fluid in the brake fluid reservoir.

 

just try to bleed the brakes. couldnt hurt.

 

I don't see that this is possible.
How would the proportioning valve know when the suspension is extended or compressed?

 

You did make sure the pads were seated first right? It takes a couple pumps to get it all tight again. Other than that if you need a rebuilt caliper it'll be leaking fluid. If there's fluid where it's not supposed to be then rebuild, if not the problem is likely elsewhere.

 

I bled the rears again friday night. I opened the lower bleeding screws this time, everything is good now. I never took the calipers off though, the FSM states you only need to bleed the lower valves if you disassemble the caliper.