I got a problem with my rear disc brakes on my 93 z in the way that they simply dont work. on jackstands with my foot hard on the brake pedal and in gear the rear wheel will turn, just barely but it does. cleaned everything up, sliders (guide pins) new pads etc. the pistons seems to move in and out freely, ( c-clamp in and i can pull em semi out with my fingers, i can also see the piston move out when i push on the brakes with a 6 foot 2x4 cause i cant be in the car and at the brakes at the same time. girlfriend is slackin off..its like i dont have enough pressure at the calipers to push the pads against the rotors.. not sure where to go from here. is there a way i can measure the pressure at the master then the caliper and compare? if someone can point me in the right direction that would be great. thx.

 

is the abs light on? brake light?

 

This could be a couple of things... First the system could just need a bleeding, it could be a going bad master cylinder or damaged brake lines. Those are the typical issues with low pressure.

Massey

 

thanks. no lights. no leaks. very well could need bleeding,thats easy n ill try it. also there is no problem to push the pedal to the floor when at a stop which probably is a problem. but when driving it stops fine...the brakes i do have engage when the pedal is high and i have no need to push it to the floor. if any of that makes sense.

 

could just need bleeding. it could be the abs brain box. i had a problem with the abs in my truck brakes and they were doin strange stuff. peddle would pulse and sometimes go to the floor but always worked. just not very good. maybe have it scanned for codes and see if theres something stored in there. i think you need a different scanner for abs.

 

man i was in a mess of brake lines this week...pretty sure my car has metric lines, like 6mm instead of 1/4 inch to the rear. very very hard to find metric thread with metric tube size fittings around here. none. so i put a standard fitting on the rear line and converted it to 3/16 and plugged it in to the master directly, just to bypass the abs. didnt seem to increase pressure to the rear. meaning at a lil more than idle with my foot hard on the brakes the rear rotors will turn in low gear on j.stands. got a mechanic buddy who works for gm come over and said the pedal feels fine, everything looks as it should. even the rear rotors turning with my foot on the brake and a lil gas was normal to him. maybe its just me???
a couple questions tho....where does the rear get proportioned? inline valve or abs? and does the master cyl put out equal pressure to both outlets? can someone jack there car up and see if does the same thing? foot to the floor on the brake, how much gas does it take to turn the wheels?

fyi- unplugging the three top elec plugs on the abs doesnt tricker the abs light. this car is quickly turning to a race car and the abs is comming out and line lock on. at 100mph (on the track) the front tires will lock up no prob if i need em too. its the rear i want to lock up or at least work better than they do.

thx in advance.

 

the back brakes are weaker, when i got done putting the new motor and trany in my car i started it and put it in gear (rear on jack stands) to run the speed up so the trany would shift up and work all the air out. while i was doing this i had the brake on trying to keep some back pressure on the motor and trans so they were working a little at least. the rear brakes did not do much to slow the motor. keep your eyes open for a ls or vette rear brake setup, bigger is better. do some searching i think you will need adapter.