I won't bore you with how we got here (Lord knows it's a long story) but let me catch you up to speed on what's going on. My '85 WILL NOT push brake fluid to the front calipers. Fluid flows freely through the lines. It will gravity bleed, and if you let it sit and accumulate fluid in the lines you can get one good bleed out of it before it goes back to pushing nothing out of the bleeder. This is of course after trying THREE separate master cylinders on the rig (more on that later). Fluid flows to the rear and the rears bleed just fine. The pedal will even start to build up some stiffness just bleeding the backs. But once you open the front for a bleed, pedal goes right to the floor. This is what we've replaced so far:

- all 4 calipers are now brand new cast ones from some Chinese company on amazon (ask me about my experience with remanned fiero calipers)
- all 4 soft hoses
- remanned power brake booster (had a friend insist this was the issue)
- rotors, pads, all parking brake cables, though that's not really pertinent here
- and finally, THREE separate master cylinders, two were remans and one (from the same chinese supplier as the calipers) claims to be new cast, but I can't find any difference between it and the remans - it looks and feels the exact same

We have taken off and blown air through all hard lines, fluid should be going through them just fine. Now, I will say, the OEM(?) master, the one that was on the car when I bought it, will push fluid to the fronts BUT there is a never ending stream of bubbles when bleeding it, makes me think a seal is bad in it because the rest of the system is leak free. It may also be of note that the original master seems to be a different metal, it looks different and is much lighter. Here's the original one:



In contrast, here's how all the ones I've purchased look:



And finally, here's what my current set up looks like:



The little blue thing is a stopper that blocks the prop. valve from closing off the front circuit, as that was an issue at one point.

That's about all I can think to tell you at the moment. Fronts just won't get fluid pushed through them. I've scoured this forum looking for others with this issue, but haven't been able to find one whose problem wasn't solved by replacing collapsed soft lines. My partner in this project/ pedal-jockey-bleeder-buddy will likely be lurking around this thread, and may even throw in his 2 cents, so look out for that. Other than that, I'm open to any and all suggestions at this point, cause I'm sure as hell out of both good and bad ideas.

Thanks,
Doggo


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This post is part of a series of threads in which I attempt to stumble my way through an (unintentional) complete brake overhaul on my 1985 Fiero. Check out the other episodes, if you're having a brake problem, chances are I've had it too!

Episode I - Rear Brake Blues
Episode II - Destroying My Brand New Caliper
Episode III - The Parking Brake
Spinoff Episode - At wits end (started by my partner)
Episode IV - Out of Ideas (You are here)

[This message has been edited by Doggo (edited 03-27-2025).]

quote Originally posted by Doggo: I won't bore you with how we got here (Lord knows it's a long story) but let me catch you up to speed on what's going on. My '85 WILL NOT push brake fluid to the front calipers. Fluid flows freely through the lines. It will gravity bleed, and if you let it sit and accumulate fluid in the lines you can get one good bleed out of it before it goes back to pushing nothing out of the bleeder. This is of course after trying THREE separate master cylinders on the rig (more on that later). Fluid flows to the rear and the rears bleed just fine. The pedal will even start to build up some stiffness just bleeding the backs. But once you open the front for a bleed, pedal goes right to the floor. This is what we've replaced so far: - all 4 calipers are now brand new cast ones from some Chinese company on amazon (ask me about my experience with remanned fiero calipers) - all 4 soft hoses - remanned power brake booster (had a friend insist this was the issue) - rotors, pads, all parking brake cables, though that's not really pertinent here - and finally, THREE separate master cylinders, two were remans and one (from the same chinese supplier as the calipers) claims to be new cast, but I can't find any difference between it and the remans - it looks and feels the exact same We have taken off and blown air through all hard lines, fluid should be going through them just fine. Now, I will say, the OEM(?) master, the one that was on the car when I bought it, will push fluid to the fronts BUT there is a never ending stream of bubbles when bleeding it, makes me think a seal is bad in it because the rest of the system is leak free. It may also be of note that the original master seems to be a different metal, it looks different and is much lighter. Here's the original one: In contrast, here's how all the ones I've purchased look: And finally, here's what my current set up looks like: The little blue thing is a stopper that blocks the prop. valve from closing off the front circuit, as that was an issue at one point. That's about all I can think to tell you at the moment. Fronts just won't get fluid pushed through them. I've scoured this forum looking for others with this issue, but haven't been able to find one whose problem wasn't solved by replacing collapsed soft lines. My partner in this project/ pedal-jockey-bleeder-buddy will likely be lurking around this thread, and may even throw in his 2 cents, so look out for that. Other than that, I'm open to any and all suggestions at this point, cause I'm sure as hell out of both good and bad ideas. Thanks, Doggo

dude double check that your master is pushing fluid. also those prop valve stoppers may or may not work on fieros. ive had various issues using them so try recentering the valve by leaving a rear bleeder open...at least youll know if the master cylinder is worth anything at that point because it should force fluid through the front.
i had a similar problem with my 87 gt and the 84 (both had major brake issues when bought...) that turned out to be a suspect prop valve on both. one is using a 2 door s10 valve and the other is using a vette one (its what we had on the shelf and we have been looking for rebuild kits or prop valves that work as intended and its been hard. s10 seems ok though) only reason im using an s10 one is the master cylinder is litterally a fiero replacement one (fierostore sells them as a "big bore" so my thinking was eh good enough for now since the early s10s share the opposite weight balance but give that 70 percent to the fronts right before lockup (tested at 85 and down to 10 mph. that 84 is quite peppy with some tuning)

[This message has been edited by cartercarbaficionado (edited 03-15-2025).]