here it is, i have a 87 rx7 gxl and i have replaced my brake booster,master cylender,checked the brake lines for cloggine,replaced the calipers (all around reman through mazda) tested my abs modul (brain thingy) and yet im still having problems. it stops me just fine,but the problem is,i can be driving normal speeds,ya know just cruising and all of a sudden my front brakes start locking up and i gotta pull over wait about 30 minutes be4 i can even start driving again (front brakes lock up completely). im not sure whats causing my problem and i 1) the closes mazda dealer is about 22 miles away and 2) it would cost me 80$ just to diagnose the problem (if they can even figure it out). im so lost here, i can't drive my car without th brakes locking up and i need to get a job and my insureince is do on the 23rd and i have no transportation other then my FC,please help me out,any and all recomendations would appreciated.

 

Did you have this problem before replacing all these components?

I ask because I've had this same issue before on a '89 323. It only started after I replaced the brake booster though. It was bad and Autozone replaced it... and my brand new pads... and my brand new rotors.

After I put the first booster in I took it for a test drive. I wound up heading straight for Autozone but by the time I got there it looked like my car was on fire there was so much smoke coming off my front brakes lol.

 

what kind of fluid did you put in it?

 

first off advanced autoparts brand brake fluid (what my family always uses). second i replaced the booster and then about a week later the master cylender went out. so i replaced the cylender the same day i got insurance, drove the car for about a week and a half and then the front brakes started locking up. It only does it while im driving and i never have problems with it happening when i stop, only when im driving. please give me any ideas.

 

is it locking up on all 4 wheels or just one? if its just one then it could be a bad piston.

 

both f the front brakes are locking up. im goin to try disconecting the abs from the front calipers,until then,if any other ideas are thought up,please let me know. i'll let u guys know if my idea works.....l8er

 

Sounds to me like maybe the front pads are binding and causing the brake fluid to boil which inturn expands and applies more pressure to the pads. You may have a sticking caliper piston.

 

you might want to check your booster and make sure the internal valving is workin properly and that the atmospheric and vacume lines are properly conected. also the vent port in the master cylender might be blocked, another thing to check is the break pedal to master cylender clearence. there is a rod that goes from the break pedal to the master cylender if the clearence between the rod and the primary piston isnt correct then it could cause draging breaks. i would start there and then move onto the booster. i highly doubt its a fluid issue. CHECK THE BOOSTER VACUME/ATMOSPHERIC LINES ARE CORRECT POSITION.

 

hey guys,i have a question. what do you mean "the booster vacume/atmospheric lines" ? im having the same brake issue and have also replaced my booster and master cylender. weird thing is,i drove the car for over a week before the problem started?

 

I would be interesting if you drove around with the brake booster vacuum line disconnected and see if this happens. Thought that might not be teh safest of ideas.

James

 

if you pull off the brake booster vacuum hose,then the car won't start....will it?i was always told it wouldn't. never tried it though...

 

Sounds sort of like you've got the pedal freeplay too tight.

See if you can push the car easily from the driver's seat when the brakes are cool and it's out of gear... if not, the brakes might be dragging, but not enough to lock the brakes until they're hot (which doesn't take long when you're dragging).

Also, you can tell if they're dragging by driving for just a few minutes and feeling the brake temperature... if they're warm, but still cool enough to touch, they're probably not dragging. If you can feel the heat from a couple of inches away after just a few minutes of normal driving, they're almost certainly dragging.

FYI, the spec for brake pedal play is 4-7mm before the power piston starts to move...although you might need to make sure that the brake light is coming on as soon as the brakes start working, especially if you've adjust the pedal height for more legroom. Just undo the carpet that covers the spare tire and you can see the third brake light light up in the rear view mirror.

BTW, you need to bleed the brakes, as you've probably boiled the fluid to hell and back already.

 

i'll deffinatly check it in the morning. if the brakes are dragging,how do i fix that exactly?

 

You adjust the push rod on the pedals... if that's not the problem I don't know what else to suggest.

 

alright,thanks alot,dude. i really appreciate it.