aborza

My '86 Sport has bad brakes for an autoX machine. I have brought it to three different mechanics and they all say the brakes are ok! I do not think they are and at an autoX training session an instructor drove my car and said I should get the brakes fixed immediately! The symptoms are a long, soft and mushy pedal throw. I cannot lock up the brakes at all and I do not have ABS!

Everything has been checked out as ok. New pads, new master cyl, no leaks anywhere, flex lines ok, new fluid, been bled multiple times by pros. No luck at all.

So now to the question. Is there a master cyl that has more fluid throw than stock that will fit on the '86 Sport vacum assist and reasonably hook up to the stock brake lines?

In any event, are there any suggestions? These brakes are dangerous. Or is it that stock 2nd Gen brakes are simply lousy?

Aaron Cake

iTrader: (1)

Stock 2nd gen brakes are excellant, even by todays standards...

Sounds like one of the hard lines is leaking, or perhaps one of the rubber lines is expanding when you hit the pedal. Have you replaced them with braided stainless?

Also, what condition are the calipers?

aborza

Thanks for the reply,

But, there are no leaks, period. Also the calipers are working just fine. Think about it. If the calipers were stuck, pedal pressure would be extreme and there would be very little pedal motion!

I have yet to go to teflon flex lines (you know the stainless covered ones ) because the OEM lines are in like new shape and I understand the teflone ones make only a slight difference in feel. My problem is a big one.

It is possible that the new master cyl is leaking internally. How does one check that without buying a new one? Hmmm.

Aaron Cake

iTrader: (1)

It is possible the master is leaking internally, since mine was before I replaced it... My symptoms were a pedal that would gradually fall to the floor at intersections, though I still had great breaking power...

I can't think of any way to test it without swapping in another. FWIW, rebuilt master cylinders are a gamble. Best to buy new from Mazda or Mazdatrix.

Aaron Cake

iTrader: (1)

Also, the master cylinder must be bench-bled before it is installed.

tesla042

I have the same problem...only I'm thinking (hoping) it may just be the pads.. I broke the bleeder screw off my FR caliper a while ago, so I couldn't bleed it... I twas REAL squishy, and i couldn't lock them up except on rain. Only recently did I replace the caliper and completely bleed everything.. It's "better", but still rather lacking. The pads still have a lot left on them, but I don't know the brand...hopefully they're just shitass brand.

Is the master cyl from a small-brake rx7 compatable on a big-brake one? I suppose I *COULD* take it off my other car if i had to...

-Tesla

Aaron Cake

iTrader: (1)

There is quite a variation between master cylinders since there were so many brake and suspension options...See http://www.mazdatrix.com/j-3brake.htm to clarify.

aborza

Yeah,

There is supposed to be a difference between all those types. But, if you note that the rebuild kit for four of those "different" master cylinders use the same rebuild kit. Hmmmm. How different can they be??

The real issue is whether a 929 or 626 master cyl has a larger dia piston and whether either will properly fit the 2nd Gen vacuum booster. I have seen that 3rd Gen (FD) 7's can easily accept the 929 master cyl. Well, what will fit the 2nd Gen (FC)?? That is the question!

Thanks!

MaxRX7

I've seen the 929 master cylinder swap in an FC, don' know how involved it is though.

If you still haven't get some SS bradied brake lines. Goodrich makes some excellent ones !

Icemark

But if you are still running with the OEM brake lines that came with your car 16+ years ago (or even 5 years ago), stainless or even new OEM lines will be a radical difference in feel.

But I would also be looking at the booster and master cyl. It wouldn't be a bad thing just to spend the $100 and replace the master, if it is again 10+ years old.

scathcart

Pressure bleeding the brakes made a big diff to my brake pedal feel.

kdxer200

aborza - Hey I'm switching the m/c in my SE tomorrow night w/ one from a GTU. I've got the same soft pedal feel and overall lack in brake feel as it seems you do. I can pm or email you and let you know how it goes if you'd like.
Also, what lines would you guys reccomend when I switch my 4 lug setup with the 5 lug from the GTU, since they are different,? Bradied or just straight rubber hoses?