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Old 04-09-2010, 01:14 PM
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rock hard brake pedal

I recently got a little 1988 fiero to zing around in this summer. It started to have a hard pedal on the way home from work also had diminished braking action.

I checked the booster and it seemed ok but I went ahead and bought a new booster.

That didn't help so I pulled the calipers off the rotors and made sire they were not stuck.

None of them were and everything was greased well so the slides should be working well.

Any ideas?

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Old 04-09-2010, 11:03 PM
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did you check vacuum source first?

make sure good vavuum from intake source is going to the booster

if not then pedal will be super hard

the GM boosters are RARE to go bad

i mean SUPER rare

like ive owned over 200 vehicles since 94 all mostly 70s and 80s cars and trucks and only once have i had a bad GM booster and it was in an 83 caprice i bought for 40 bucks with less than 100k on it.

i found a brand new one in the junkyard on another caprice, for 40 bucks and swapped it out

the check valve may be bad also

in the vacuum line to the booster

make sure its working and not blocked

they do go bad sometimes.
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Old 04-10-2010, 01:37 PM
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The Vacuum is great. The check valve checks out but I Replaced the Booster anyway and still have the hard pedal.


I Guess the master Cyl is next.
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Old 04-10-2010, 01:48 PM
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Quote:
Originally Posted by Deezildennis
I recently got a little 1988 fiero to zing around in this summer. It started to have a hard pedal on the way home from work also had diminished braking action.
Providing that there's no excessive slop in the hubs (allowing the rotor to kock sideways), replacing the pads will likely cure the problem. Even if they look to have decent material left, they will get to a point and bind. Replacing the calipers will also cure the problem, but the pads are cheaper even if you don't get the full life out of them.

If you want to fix it right, rebuild or replace the calipers along w/the pads and turning/replacing the rotors.

Do be sure the check valve's functioning as it should.
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Old 04-10-2010, 02:21 PM
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If the pedal is rock hard and the brake is not working well you could also have collapsed rubber lines. Try opening the bleeders and see if you can push fluid out. I have seen this a few times. You also could have binding calipers as mentioned in the previous post.
If the pedal moves freely with the bleeders open then the master and the booster are not your issue.
Do the bleeders one at a time with some help so you dont introduce air into the system
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Old 04-10-2010, 04:09 PM
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Check valve is fine I have replaced it anyway but I Cannot get the back brakes to bleed.

Check valve is fine, pads are new as well as the Booster.


If I Crack the line at the rear calipers it will drip very slowly but it doesnt do anything when you step on the brake no spray like you would get it it had pressure going back there.

When I crack the lines at the master and press the pedal I see fluid escape past the threads.

I Pulled the proportioning valve switch and the switch is still centered so it should be ok.
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Old 04-10-2010, 06:18 PM
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Check the rubber line look to see if and or an metal line is pinched
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Old 04-10-2010, 09:56 PM
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All the lines look great. I traced them from the mc to the calipers and no crushed lines anywhere.
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Old 04-11-2010, 02:01 AM
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See if you can reach down w/your hand or hook a foot behind the brake pedal and see if you can pull the pedal up from where it is at rest.

I suppose there's the possibility the proportioning valve has gone bad- I've never had it happen, though.

If you wanted to remove the prop function to see, disconnect the brake line going into the large fitting on the end of the combo valve, remove the fitting then the rubber valve inside the combo valve and reinstall the fitting and brake line.

Last edited by cobalt327; 04-11-2010 at 02:07 AM.
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Old 04-11-2010, 03:30 PM
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I was able to take the main rear single line off going to the rear brakes off of the prop valve and put a finger over it while the wife pumped the brake slowly. I got fluid out of that end under pressure.

I guess it had a major air block in it? I hurried up and screwed the line back in and put a vacuum pump on the farthest away caliper and pulled vacuum while she pumped. I was then finally able to get fluid back to the calipers.

I still dont think I got all the air out for now I have a mushy pedal.

I think Im going to say the hell with it and just let the local brake place fix it.

At least I can drive the dang there now though..
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