brake issue need help

[3kgt2nv]

The issue i am having is both of the front calipers today randomly got stuck at the same time.

the calipers were just rebuilt last year and the master was replaced with a gen 3 master about 6 months ago.

the fluid was totally changed at the time that the master was installed and they were all vacuum bled to remove all the air

if it was just one caliper that sized to the rotor i would think that the caliper was bad after the rebuild but both of the fronts instantly got stuck at the same time has me leaning towards the master or if the prop valve can go bad. I had to crack the bleeders open to release them and fluid squirted out under pressure so its like the lines are not allowing fluid to release the calipers.

neither of the rears were stuck so im confused about the master because i thought the master did 1 front 1 rear on each circuit

any help is appreciated

 

[CSFX8588]

Bad proportional Valve? I've never had a problem with one but seems like one way for the fluid to get caught going to the front.

Did you change prop. valves when you did the ABS Delete?

 

[chaclark83]

Check your caliper pins. Never mind. Just realized you said fluid sprayed when you cracked the bleeders. The lines are definitely in question. Also must ask. Does it have abs?

 

[Lou98GSX]

your master sends fluid to the proportioning valve and that valve splits the pressure l/f to r/r . i have seen brake hoses collapse and cause this problem .

 

[CSFX8588]

Sorry, forgot my setup isn't what they had stock.

 

[3kgt2nv]

Non abs car. Prop valve is the original so it could be suspect. Since its both fronts at the same time i was hesitant to suspect the lines but i will start with checking the calipers over since the pads are garbage from the block drive home with them stuck and do the lines next. If still having the issue a new prop valve will get ordered

 

[3kgt2nv]

just an update. after looking at all the options i am tempted to think it is the prop valve being to restrictive with the larger master and the greater capacity of the calipers. I have ordered the 1g "big break" prop valve which is definitely larger than the 89-90 prop valve and have it installed. next step is to bleed the the breaks and give it another shot.

 

[3kgt2nv]

another update. breaks arent locking up any more but definitely feels like there is some very slight dragging going on with the rotors.

 

[oldman_tau]

check if its rusted inside it happened to me lately

 

[3kgt2nv]

the calipers? they were rebuilt and new seals and boots installed

 

[3kgt2nv]

just to update. the stock adjustable rod that actuates the master cylinder was about 2mm out of adjustment and was putting just a tiny bit of pressure on the master causing the brakes to drag and after several stops the pressure was high enough to cause them to lock. i readjusted them and have had zero issues.

unfortunately i replaced the prop valve and the brake lines before i figured to check the rod.

 

[steve]

The rod from the booster to the master needs to be the correct length or the master cylinder piston won't return to uncover the port that releases the residual pressure.

 

[3kgt2nv]

ding, ding ding,

atleast now the brake system has totally been replaced

 

[redbud23]

It sounds like a proportional valve. I had the same problem with my chevy truck once and I replaced everything before I found out about the valve.