I've been working with a brake issue on my recently acquired 86 GT. Soft feel and long pedal travel. Brakes work and feel fine until a point is reached on the pedal and then the resistance fades a bit and the pedal travel extends.

While looking at various brake components on-line I noticed that there seems to be two very different looking master cylinders. The one on in my 88 GT is flat and horizontal. The one in my 86 GT looks the same (flat and horizontal). But when I see them pictured on web sites one of them (I believe the earlier model) has a significant slope to the reservoir and the cap sits at a pronounced angle.

The PO told me about the brake issue. Said the master cylinder had been replaced but it did not fix the problem he was having. So I know it has been replaced at some point in the past.

I am at work and can't get actual photos right now but here is a pic that looks like both of mine, and a pic of the sloped/slanted one. (Pics are from the Fiero Store web site)

This is what it looks like on both my cars. The 86 and the 88:



This is the one with the sloped reservoir cap:



So, do I have the wrong one in my 86? Could this be the reason for my brake problem?

------------------
John Wayne as John Bernard Books in The Shootist...
" I won't be wronged. I won't be insulted. I won't be laid a-hand on. I don't do these things to other people, and I require the same from them."

My rides...
1988 GT with a 3.4L V6 automatic
2006 Harley Sportster
'cause I love the twisties on two wheels or four.

...

[This message has been edited by tshark (edited 09-08-2018).]

Comparing tanks means nothing to the MC. Several tanks will fit the same MC.
The tank on lower picture are use to clear the sun roof glass storage area. Store etc often only carry this to lower inventory numbers.

Your MC could be bad or sadly, PO used wrong MC.
Many have bought Big MC from TFS for use on stock brakes but problem is that Big MC reduces stopping power w/ stock brakes. TFS only recently added do not use on stock system.

If someone tried to "upgrade" the brakes and did not "upgrade" the MC then stock MC could too small.

I would need more info to say what might be wrong.

Many problem answer here...
See my Cave, Brake Service

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

quote Originally posted by tshark: The angle isn't as dramatic as the images suggest. I had both years of Fiero. I'm down to just an '88 now, but the master cylinders were the same. The brakes work, otherwise, right? The MC was already replaced with no change. I think you should look elsewhere. Could the booster be leaking vacuum? How are the brake lines? Could there be air in the lines? How about the valve?

I don't know... Looks pretty steep to me. There must have been a reason for it?



The brakes work, but not correctly, as I described above (soft pedal - long travel). So far I have bleed the lines and attempted to correct/adjust the parking brake which has very little resistance to the handle pull. Visually I can see that the pistons do extend a somewhat when the handle is pulled but not enough to hold the car in place. I've replaced the chewed up equalizer but no amount of adjustment has made any improvement om that front.

I've raised both problems in a separate thread and am still working through that.

https://www.fiero.nl/forum/Forum2/HTML/135017.html

Yes, the OP told me he had brake issues and that the MC was changed out, but I don't know which one was in there originally. The flat one or the slanted one. He was not happy with the mechanic that did the work and I thought it might be possible he put the wrong one on it. I believe the booster was changed out at the same time.

As for which problem to tackle first, I've been told different things by well informed folks on here. I've been told to fix the brake pedal issue first and other have said to fix the parking brake issue first. I've done some work on the simpler aspects of both systems so far hoping to get the easiest one corrected first.

I am hoping for a definitive answer about the correct Master Cylinder since I don't want to chase something that might already be staring me in the face.

Thanks


EDIT...I was working on this post when theogre posted his reply..... Seems I've got my answer on the reason for the slant. Thanks!

[This message has been edited by Rsvl-Rider (edited 04-23-2015).]

These style tanks are normally used on applications where the brake booster mounts at an angle to the firewall. Notice the fluid level fill line will never be horizontal when installed in a Fiero. At a minimum, the tank is incorrect for the Fiero application.

MC height and angle are same after install. (Car parked on level ground.)
Small tank lid/top is level after install. I have it OE because car have sun roof. (called "Vista Vent" option.)

Assuming is are stock...
"soft pedal - long travel" points more to low pedal problem because Bleeding won't help Low pedal.
Low pedal often cause by rear caliper problems.

Adjusting P-brake using any method may help but often is temporary fix or does nothing.
Very likely have bad rear caliper(s), cable(s) or both.

Pads should move very little... normal op very close to touching all rotors.
Iffy wheel bearing can cause pad clearance but most times is bad rear pistons causing low pedal.

Also See my Cave, Rear Brakes

Note... If PO use 88 MC on 84-87... 88 is too small and can cause low pedal.

The 88 -87 brake masters are different.... And indeed look different so if they looks the same you probably have the wrong one. On a side note, i have been using the stock master with beretta calipers on the 87 GT and i like the pedal feel at first the pedal was low and i taught that I was needing to replace the master but it was just that the calipers were hitting a corner of the base, once I adjusted the base the pedal travel back to the top. No need to chage the master with the big bore one.

Here are factory stock master cylinder pictures installed in the cars. The '84 is the only one without a factory sunroof.

You can't even swap tanks on the two units illustrated by the OP. Notice the cast pedestals on the MC are different heights. They are intended for different applications. The bottom of which isn't for a Fiero.

For what it's worth, a few years ago the fiero store sold me a MC that's cast iron, not aluminum like the orig. It bolted-up and seems to work, just rusty on the outside now as expected. It is absolutely impossible to lock any wheel when braking. Maybe the FS received a batch of incorrect masters?

I apologize, I thought the orig. post mentioned that the master came from TFS.

[This message has been edited by donuteater306 (edited 04-24-2015).]

quote Originally posted by theogre: The tank on lower picture are use to clear the sun roof glass storage area.

Uh, no.......
This information is incorrect.