my friend has a 91 civic non abs civic, with a built ls/v and rear disc conversion. we've been having this problem where the brakes are cool and after about 15-20 miles all 4 wheels just lock up. weve changed the booster, prop valve, and bled them. can this be a master cylinder problem? it doesnt sink to the floor or anything. thanx for the help

 

Sounds like MC is the only part left really. When you say lock up are you hammering the brakes or just tapping? Hows the pedal feel, hard soft?

I know when my MC went out the pedal was sinking. I also had issues with a rear caliper locking up/getting hot and so far new rebuilt calipers in the rear seemed to have fix that "knock on wood"

 

the pedal is cool until they lockup, then its hard. im just using the brakes normally and its all 4 wheels. it has stainless steel lines, i thought could be the culprit but the chances of all 4 messing up are slim to none, correct?

 

That is very odd, what brand lines btw? Maybe something not right with the lines? Swelling etc?

 

like goodridge or something, i told him id lean towards the lines since you cant see them swelling cuz of the stainless steel. whats the best thing to lean towards? lines or master cylinder?

 

What fluid he using? I am almost leaning towards lines, but thats odd all 4 bad

 

It sounds as if one or more brake calipers are locking up. Try removing and cleaning the brake calipers. Use good quality high temperature grease when you put them back on. When you finish the caliper install, make sure that the calipers clamp and release with ease.

 

I would double check and flush all the fluid. For all 4 brakes to lock up you need response from the MC somehow. Either the MC is faulty or pressure is building as you drive. Flush all fluid and replace it with fresh dot3. Also check the pedal and linkage you might have a break in one of the welds constructing the pedal assembly.

 

ok well the fluid is all brand new dot 3. and he recently got the car so i dont know what was done to it to cause the problem. i want to get him to get rid of the lines for some stock ones before anything

 

all 4 are locking up. when it happened we jacked it up corner by corner and all the wheels were locked

 

prestone, dot3

 

brake pedal to MC pushrod clearance too small. under heating expanding hydraulic fluid pushes the piston out just a bit, without the proper clearance the MC rod will be there and the brake will be to drag, heating the fluid...causing more dragging....

Theres a locknut and adjusting nut..trying backing it off a touch.
Or get the brakes hot and then backing it off so they dont drag.
or get some feeler gauges or whatever that expensive tool is.

 

^ this

 

Good info "andyz" I hope that's the problem because that's a relatively easy fix.

 

wheres the pushrod and how do i adjust it? is it behind the brake pedal?

 

Yes.

 

Very Helpful thread for me thanks honda tech !