I replaced the two rear hoses. I overhauled my rear calipers. The front hoses and calipers are in "good enough" condition. I double and triple checked that I bled all the old fluid and air out from each of the calipers. With the car OFF, and a few pumps, the brake pedal stiffens. When the car is RUNNING, I hear a hiss and the pedal can be pushed straight to the floor with ease indefinitely. I notice what appears to be "splashing" going on in the MC reservoir when pushing the brake pedal whether the car is running or not. I've read it could be a booster and a MC issue. Last night I bench bled the MC and put it back on the car. Had a friend press on the pedal, I cracked open and then closed the front line, my friend depressed the pedal and repeat for rear line. I'm still facing the same symptoms.
What would you do next to figure this out? Should i plug the MC lines and see how the pedal feels to narrow down the window of failure? Should i buy a MC overhaul kit and do that next? Replace the booster? Thanks yall.
MC is bad. Likely bad before then pedal bleeding did the rest. Replace it, Do Not rebuild. Rear calipers may still have problems making more low/floored pedal problems. DIY Rebuilding Fiero rears is often a wast of time and money. See my Cave, Brake Service and rest of brake section.
Booster is Not your problem. Air Noise is just Air moving in the booster when you floor the pedal and engine off will get very hard pedal as booster Vacuum runs out. The white Check valve on the booster is ok too because you can push pedal 1 to several times w/ engine off. (Floored pedal problems then vacuum reserve runs out faster.)
------------------ 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)
MC is bad. Likely bad before then pedal bleeding did the rest. Replace it, Do Not rebuild. Rear calipers may still have problems making more low/floored pedal problems. DIY Rebuilding Fiero rears is often a wast of time and money. See my Cave, Brake Service and rest of brake section.
Booster is Not your problem. Air Noise is just Air moving in the booster when you floor the pedal and engine off will get very hard pedal as booster Vacuum runs out. The white Check valve on the booster is ok too because you can push pedal 1 to several times w/ engine off. (Floored pedal problems then vacuum reserve runs out faster.)
Thanks for the response! I have read through a few sections of the Cave, it's been helpful! Thank you for your service! Advanced Auto Parts has the MC in stock about 20 minutes from me for $80, it's cast iron... Is there a better online option you suggest for the MC? I don't think there's any fieros in junk yards that I can pull parts from. Few and far between in Utah.
[This message has been edited by WaterInYuhDish (edited 12-17-2021).]
That listing is wrong. Either wrong part total or wrong entry on the web site etc. All Fiero MC are aluminum.
Pic looks right but description say cast...
Can buy online from AA web, and AZ web, and return core to nearest store. If can't use, return new unit to store too.
AZ has New MC for 84-87 that doesn't core charge They say "Master Cylinder Material Aluminum or Cast Iron"
Used MC is likely bad. Don't bother.
Finally got around to changing out the old MC and put in a new one. Same issues as with the old MC, yay... is the brake booster the next culprit? Someone told me it could be a vacuum leak but I'm unfamiliar.
It shouldn't be the booster since it's a hydraulic system and despite being easier to push, it should never go to the floor. I have a feeling (having ruled out the master cylinder) that you either have air in the system that is being really stubborn, or a bad hose (check the front hoses since you already swapped out the rear ones).
Fieros are known for being very difficult to properly bleed. Many people swear that they've properly bleed the system yet ultimately they find trapped air after days of cursing.
Did you bench bleed the new MC before you installed it? If not, you may want to redo it to make sure there is no air in the new MC.
I agree with another poster, change out the front hoses and re-bleed the entire system. Start with the caliper furtherest from the MC and work inward. If you have a manual, forget the order it suggests. The correct order is LR, RR, RF, LF. I've been "gently" corrected on this several times (Thanks, Patrick ;-D) .
[This message has been edited by Mike in Sydney (edited 01-07-2022).]
If memory serves, if the rear brake pistons aren't adjusted properly, this can cause the issue you're describing.
I've got two Fieros, and what you're describing is what's happening with my project car.
I'm not going to bother to install them properly until I can replace the cradle, since I'd have to replace the ebrake line through the cradle, that would just be added work
Did you bench bleed the new MC before you installed it? If not, you may want to redo it to make sure there is no air in the new MC.
I agree with another poster, change out the front hoses and re-bleed the entire system. Start with the caliper furtherest from the MC and work inward. If you have a manual, forget the order it suggests. The correct order is LR, RR, RF, LF. I've been "gently" corrected on this several times (Thanks, Patrick ;-D) .
I did bench bleed before putting the new one on. And I have bled in the proper order for the manual trans. I rebled the lines again yesterday and still nothing. Another post suggests the rear brakes not being set properly could be the issue which I know I haven't reset the calipers/ebrake properly since overhauling those calipers, the cable on the driver side is pretty deep in the spring so it was a pain to get to after putting everything back together in one go so I put it off for another day. I guess that time has come. It sounds like the pads are dragging now too.
[This message has been edited by WaterInYuhDish (edited 01-10-2022).]
If memory serves, if the rear brake pistons aren't adjusted properly, this can cause the issue you're describing.
I've got two Fieros, and what you're describing is what's happening with my project car.
I'm not going to bother to install them properly until I can replace the cradle, since I'd have to replace the ebrake line through the cradle, that would just be added work
If this is true. That very well is my problem. I have yet to get the driver side ebrake cable pulled through to set that and adjust the calipers/pads. So I think that will be my next move.
Pull the cable through the spring to get that seated. Adjust the parking brake/caliper/pads as needed.
If memory serves, if the rear brake pistons aren't adjusted properly, this can cause the issue you're describing.
I've got two Fieros, and what you're describing is what's happening with my project car.
I'm not going to bother to install them properly until I can replace the cradle, since I'd have to replace the ebrake line through the cradle, that would just be added work
Took another crack at it and I cannot pull the cable through to the tab where it's suppose to seat on the caliper bracket. Somehow it seems to have lost length after removing it and no amount of strength will get it to stretch far enough. Is there a way to add some give for the cable and tighten it up after? I looked through my manual but I didn't find much that seemed to help with my specific issue. Adjusting the parking brake portion even was a little vague. Will take a look through the cave soon enough.
If you read the whole quoted section the context should help you. I found that the LR brake line is the longest for my fiero. So that's the first one i bleed.
If you read the whole quoted section the context should help you. I found that the LR brake line is the longest for my fiero. So that's the first one i bleed.
A "manual trans" has nothing to do with bleeding the brakes. In your quote of Mike, he's referring to the service manual, not the transmission!
quote
Originally posted by Mike in Sydney:
If you have a manual, forget the order it suggests. The correct order is LR, RR, RF, LF.
[This message has been edited by Patrick (edited 01-11-2022).]
I see. I misread. And I've seen so many people say one or the other I guess my brain filled in the gap with it being something to do with the transmission.
Took another crack at it and I cannot pull the cable through to the tab where it's suppose to seat on the caliper bracket. Somehow it seems to have lost length after removing it and no amount of strength will get it to stretch far enough. Is there a way to add some give for the cable and tighten it up after? I looked through my manual but I didn't find much that seemed to help with my specific issue. Adjusting the parking brake portion even was a little vague. Will take a look through the cave soon enough.
which cable? you may have to adjust the tensioner that goes between the cables to allow more slack.
if your cables are rusted so that you can't work with them, they're not terribly expensive, I'd replace them.
Ignore P-brake cables right now. (Unless keeps Brake light On, then pull main cable in back to shut off light when messing w/ handle.)
P-brake cables won't matter to fix pedal to floor problems.
No leaks and still floored pedal mean big air problems and/or calipers/piston(s) causing huge pad clearance problems.
Good rear pistons will self adjust Without the P-brake cables attach to them. R-calipers only need external P-brake springs to keep lever at resting stop so won't move when normal brakes are used. Good sliders and their "o-rings" and proper install will help too.
Hoses will Not cause floor pedal w/o leaking. Hoses will fail in very obvious ways and leak bad at minimum.
MC tank will "spray" fluid. More so w/ low or floor pedal problems because quick take-up section dumps a lot of extra fluid. See my Cave, Quick Take-up notes
Ignore P-brake cables right now. (Unless keeps Brake light On, then pull main cable in back to shut off light when messing w/ handle.)
P-brake cables won't matter to fix pedal to floor problems.
No leaks and still floored pedal mean big air problems and/or calipers/piston(s) causing huge pad clearance problems.
Good rear pistons will self adjust Without the P-brake cables attach to them. R-calipers only need external P-brake springs to keep lever at resting stop so won't move when normal brakes are used. Good sliders and their "o-rings" and proper install will help too.
Hoses will Not cause floor pedal w/o leaking. Hoses will fail in very obvious ways and leak bad at minimum.
MC tank will "spray" fluid. More so w/ low or floor pedal problems because quick take-up section dumps a lot of extra fluid. See my Cave, Quick Take-up notes
There's no fluid leaks anywhere. There's no pad clearance issue as far as I can tell, either. I'll read through your link here in a moment. Was thinking of clamping the vacuum line to the booster shut to see if there's any difference. Just need to pick up some vice grips unless you have an alternative to test for a vacuum leak?
which cable? you may have to adjust the tensioner that goes between the cables to allow more slack.
if your cables are rusted so that you can't work with them, they're not terribly expensive, I'd replace them.
If the tensioner is the little assembly located just behind the rear of the craddle, then yes. I was playing around with that to see if I could get any more give in the ds cable, but it didn't seem to make a difference. Might be that it's rusted on the ds.
With the car OFF, and a few pumps, the brake pedal stiffens. When the car is RUNNING, I hear a hiss and the pedal can be pushed straight to the floor with ease indefinitely.
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Does the pedal go all the way to the floor or just close to the floor? Also, do you know if the brakes are actually holding when the pedal is pushed? Try putting the car on jack stands and taking off the off the wheels. Can you turn the brake rotors when the pedal is pushed with the car running?
Booster/vacuum problems Will Not cause a low/floored pedal.
Air sound when pushing a low/floored pedal is Normal. Sound is a lot of air moving thru the control valve to help you pushing the pedal. Can even try to stall the engine because act as a big vac leak during flooring the pedal.
Sound will stop only when MC has enough pressure to push back on the booster output pin. Sound may not stop when you have hydraulic problems because the booster can go "out of range" and control valve gets confused trying to floor the pedal.
In normal braking, the sound is often still there but less air used means less noise you hear. Many vac boosters have things to reduce normal noise or other design features so can't hear air noise in most settings.
Don't crush big vac hoses to test. Can wreck old ones like that. disconnect the hose and plug the open end. Just make sure the plug is made so can't get sucked down the hose/pipe. W/o vacuum the booster will fight you pushing the pedal.
