I just recently did a brake swap on my 92 cx here is the set up
99si front and rear brakes stainless lines rs booster (junk yard) and master cylinder (new) 93 si proportioning valve
now the problem I am having
some times the car will drive fine and stop fine and then the brakes lock up on there own
I blead the system 4 times last night after gravity bleeding it for 2 hrs and it worked fine last night but today was the worst ever I locked up so bad I couldn't even drive I had to open the bleeder nipple to release the caliper to get it home
I am tired messing with it
and help would be greatly appreciated thanks
Jason
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Need more details. Do all the brakes lock or just one? The brakes apply themselves? They lock without you pushing the brake pedal? Have you checked the pedal adjustment? There should be a certain minimum freeplay measured at the pedal. It is adjusted by changing the length of the pushrod.

 

all the brakes lock, they apply themselves without me pushing the pedal

 

If you have abs it's probobly that...

if not it's a malfuntioning booster I would assume...

does the pedal drop too?

 

no
pedal gets stifffff as helll

 

bump for jason...someone's gotta know whats up

 

I'm not sure I can check tomorrow but I think that's a good sign the boost is all f'd up....

 

Brake booster seems like the most likely cause. If you can deal with the brakes being really stiff, disconnect the vacuum line to the booster and plug it to prevent a leak on the engine side. Then give the brakes a shot. Why didn't you use the correct booster for the master cylinder? Some parts that bolt up do not always mix and match well or it could just be a bad booster.

 

the booster is for a 94 rs so is the master cylinder

 

order a replacement... i'm pretty positive you have a clear case of a bad booster...

as I said I can double check for you tomorrow if no one else can confirm it.

 

anyone else care to confirm

 

Oops, I read it as the mc for the 99 Si and just the booster from the RS. Yeah, so far as I know the brakes from the Si are the same as the RS. It does not say, but I assumed there is no abs stuff on this one since adding it to a car that did not come with it is a really big pain so I did not consider anything from the abs that could cause this problem.

Since all the brakes are coming on, it has to be something applying the master cylinder which makes me think booster. Is it possible the pushrod from the pedal to the booster is adjusted too tight? Is there enough freeplay? That could, in theory, cause problems, but I think that would just make the brakes drag a bit, not lock up.

 

thanks will look at it tomorrow