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Brakes squishy even after bleeding twice


ColdScrip
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I am going to try bleeding all the brakes more but I was wondering if anything else could be the factor. With the engine off and after bleeding the brakes the pedal feels nice and stiff. The second we turned the engine on the pedal was very squishy. We bled them again and the same issue occurred.

 

Brake booster was not replaced during my restore and it was also not messed with in terms of adjustment. Could an out of adjustment brake booster cause such an issue?

 

New SS brake lines, rebuilt calipers, no leaks anywhere that we can see, and a rebuild master cylinder.

 

Any ideas?

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Bleed them out some more. If you haven't done it already start at the right rear, and bleed it until you get clean fluid out of it. Make sure to keep the reservior full. Then do the left rear, then the right front, then the left front. It's what I did when I put my 88 on the road. Been fine ever since. I don't ever seem to have anybody around when I need to bleed anything, so I got one of those one-man-bleeder kits. Just a little cup with a couple sections of tubing and a couple rubber fittings. Works like a charm.
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go ahead and adjust the parking brake if you have not,,that is part of the rear caliper pad adjustment ,you can also engage the parking brake when bleeding the rear calipers

 

also with new pads and old rotors it may take a bit for the pads to wear in or conform to the old rotors sufrace , petal will get better with some driveing and useage

the brake petal will have a firm feel but not a rock solid feel while seting still

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Ya keep bleeding them until you have new fluid at the rear calipers there is a very long length of line and unless you keep it up you'll not get bubbles out completely. There is too many chances for you to just get out one pedal of fluid and then tighten the bleeder, pump the pedal again and open the bleeder and have that bubble go back and forth unless you hurry it up. Can't let the pedal return until you close the bleeder but you know that already. You can put a hose on the bleeder and let it dump into a bottle but I still prefer the two man way to pressurize the system and you open the bleeder and let it blast out the fluid and the air and get it over with.
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my brakes have been soft and mushy since i put mine back together, like you i had the booster and everything down. they werent that way when i took them apart but they are now. same symptoms as yours, pedal is nice and stiff when you bleed them or the car is not running, soon as the booster sees vaccum my pedal goes to the floor.

 

i had to replace a leaking rear caliper, and rebuilt the front caliper mounts cause my slides were sticking. i have knoticed some dribble from the back of my master so that could be some of my problem. if not its got to be in the booster cause we have bled my brakes over and over and over. we have pump bled them with two people, we have mighty vaced them and they are still soft and mushy.

 

you get used to it after a while. but forget about it once and your nose planting into the windsheild, they are soft but they still grab like no other. i make it a point to give myself plenty of stopping room cause it will make the car fishtail cause it seems they are stronger out front.

 

i too also have my abs eliminated and have flushed out all my lines and the splitter box. its just one of those unsolved things.

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my brakes have been soft and mushy since i put mine back together, like you i had the booster and everything down. they werent that way when i took them apart but they are now. same symptoms as yours, pedal is nice and stiff when you bleed them or the car is not running, soon as the booster sees vaccum my pedal goes to the floor.

 

i had to replace a leaking rear caliper, and rebuilt the front caliper mounts cause my slides were sticking. i have knoticed some dribble from the back of my master so that could be some of my problem. if not its got to be in the booster cause we have bled my brakes over and over and over. we have pump bled them with two people, we have mighty vaced them and they are still soft and mushy.

 

you get used to it after a while. but forget about it once and your nose planting into the windsheild, they are soft but they still grab like no other. i make it a point to give myself plenty of stopping room cause it will make the car fishtail cause it seems they are stronger out front.

 

i too also have my abs eliminated and have flushed out all my lines and the splitter box. its just one of those unsolved things.

 

I am going to try bleeding some more but I am leading towards this issue not being resolved by simple bleeding. Gurus, if the entire braking system is taken apart what can cause something like what cyberquest is experiencing?

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have you checked to see if any of the brake lines might have a crack in them?

 

erins car is the same way...you push the brake pedal, it goes to the floor (or close)...then it feels like you hit a wall and the car brakes...lol

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have you checked to see if any of the brake lines might have a crack in them?

 

erins car is the same way...you push the brake pedal, it goes to the floor (or close)...then it feels like you hit a wall and the car brakes...lol

Lines are new SS ones from jolyrgr. I will inspect everything for leaks next time i'm out there. Is it possible for the brake booster to boost "too much"?

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and do not pump the petal like your rideing a bike,, fast pumping can lead to air bubbles in the fluid , and air tends to try and stay in the highest part of the line,, so start at the highest place, the master,,

 

one reason i sugest'd you apply the parking prake is to stop piston movement , you will actualy get farther by bleeding one rear and one frt at the same time,,this alows the master cyl to make a full piston stroke , but ANY leak or signs of wetness can alow air to suck in some times with only a wet spot to show it's leaking, air is thiner then brake fluid so it'l pass thru an opening much smaller the the fluid will,,

 

normaly the petal heigth is control'd mainly by the rear brake system , any wet on the master cyl inner bore says it's leaking and posibly sucking air on the up stroke , this means you may never get all the air out cause it's being replace'd with each pump of the petal , a caliper can do this as it pushes out and relax's after pressure is apply'd and remove'd

 

you have 6 bleed points 4 calipers the abs unit and the master cyl

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I had two leaks. I fixed those and the problem persists. However we did come across some information on the problem. Even though the pedal is very squishy, with the car on the front brakes engage with a very slight amount of pressure. The issue though is that the rear breaks do not engage until most of the pedal has been pushed down. Bled the brakes with a mighty vac as well so the air should be out of there. How do the rear brake caliper pistons adjust? It seems like it is too far back. Any ideas given this information? Edited by ColdScrip
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Craig may well be right. But as was pointed out earlier by the old rookie is the rears account for the pedal stiffness. I can attest to it cause I just did rear calipers for the second time in 20+ and my pedal went stiffer than I thought it could. If you haven't pulled rear calipers and gone thru them - not so promising. But I thought you had. They pull back just enough when you let off the pedal. They only move along the slide pins any real distance for wear compensation. The ebrake moves the piston by direct leverage just a bit to tighten it to the disc. It springs back when you release unless it or your cables are frozen up.

 

I suppose there is a proportioning valve back there that could cause you trouble as well but I haven't messed with one. PQ has that on trances board.

 

Bench bleeding the master is key too. It keeps you from pushing air all over the place to an exit.

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Craig may well be right. But as was pointed out earlier by the old rookie is the rears account for the pedal stiffness. I can attest to it cause I just did rear calipers for the second time in 20+ and my pedal went stiffer than I thought it could. If you haven't pulled rear calipers and gone thru them - not so promising. But I thought you had. They pull back just enough when you let off the pedal. They only move along the slide pins any real distance for wear compensation. The ebrake moves the piston by direct leverage just a bit to tighten it to the disc. It springs back when you release unless it or your cables are frozen up.

 

I suppose there is a proportioning valve back there that could cause you trouble as well but I haven't messed with one. PQ has that on trances board.

 

Bench bleeding the master is key too. It keeps you from pushing air all over the place to an exit.

 

This is what is confusing me. I did rebuild the calipers. The e-brake works perfectly and it is adjusted correctly. Yet where the pedal is squishy the fronts engage and the rears do not. Then when most of the pedal distance has been traveled, the fronts are rather tight and the rears just begin to brake. I find that rather odd. When the rears begin to brake the pedal feels tight. As a result the pedal only feels tight when it is practically pushed all the way down.

Edited by ColdScrip
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what do we have fo a propertioning valve? to lazy to look at my car.

 

open the right front bleeder screw and stomp the pedal to the floor with the bleeder open hold pedal dowm shut the bleeder and then restart the bleeding sequence.

 

last ditch effort make a pressure bleeder rig. google is your friend.

 

the other thought is while bleeding the master tap (not hit) the side of the master with a hammer.

 

 

 

 

flame suit on.

 

I never bench bleed master cylinders never have never will.

 

when bench bleeding a master many people overstroke the cylinder that can cause premature wear and deformation of the seals...... and it takes way to long to do.

 

 

I just put a suction gun up to the master port and pull vacuum on the port wich will pull all fluid through.

gm, h bodys you can change and master bleed with suction gun and have to car on the road without opening the rear bleeder in less then half an hour.

 

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So your still thinking air in the lines? We had a vacuum pump hooked up to each bleeder for awhile and thats all after bleeding them with two people twice. As for the proportioning valve we have one that is located on the firewall. One end goes from the master cylinder to the valve. (W/O ABS). I believe the other end connects to the line leading to the rear brakes. How do they work? Obviously it is letting fluid get to the rear but what exactly does it do? Edited by ColdScrip
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on this car the basic funtion of the proporting valve is to delay the rear brakes from working just a tad so the frt brakes can apply first , it has a spring load'd valve that first must open to alow pressure to the rear brakes it also alows the pressure to bleed off once the petal is release'd

 

couple questions from your first and 2'd reply i gather you remove'd the ABS unit,,

and when bleeding the master , how are you doing it

you should be able to get all air from the master by lossening all lines and alow to drip untill just fluid comes out then tighten the lines and pump the master a couple times lightly

 

you do understand the petal will be much diff from when there is no power assist and when there is,, you can test the booster for power by alowing the engine to idle for a couple minutes,,with out touching the brake petal, turn off engine,, apply the brake, do you hear a slight whish as you do,, let the petal up and repeat, you should be able to get 3-4 aplications of the brakes with assist, before the petal gets hard ,, if not the booster has an internal leak ,if the booster goes rigth thru the assist with a long whish , it may be whats call'd an atnospheric valve malfuntion internaly with in the booster , eather way not holding vacuum or pushing thru means the booster needs replaceing

 

back to what i mention'd earlier about the rear of the master showing leakage,,that is the chamber for the rear brakes, if it sucks air the rear brakes will not have the full stroke pressure avaliable to it , if you drip bleed the master and the rear chamber shortly shows air in the master again the internal seals are sucking air in when the petal is let up

if eather side of the master will not bleed thru,,it normaly means the piston is not comeing completely back and opening up the flow thru port , if that is so you need to measure the booster actuateing rod length , the manual tells you exactly how to do that

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You said you rebuilt the brakes. It may sound dumb but are your bleeders on top or bottom? My buddy switched his calipers once and installed them on oppisite sides with the bleeders pointion down and it took him forever to figure out what was wrong.
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Thank you for the replies. The calipers have the bleeders upright. ABS is removed. Shelby, I have not bled the master as I was trying not to to avoid a mess in the newly painted engine bay. However now it seems that I must. I will bleed it with two people: one to hold the pedal while I brake each line loose until just fluid comes out. I will also try bleeding the rears again with the parking brake engaged.

 

I completely understand how the pedal is to feel quite different between the car on and off. We have several quests here and my brother's quest has a much stiffer pedal than mine when the car is on. I went through some service manual tests for the brake booster. It seems to operate properly. With my foot on the pedal, I start the car and the pedal moves down slightly. It takes about 3-4 pumps to bring the stiffness back to the pedal with the booster off. No whoosh sounds but I will double check that.

 

The master is an A-1 Cardone reman. Shelby, when you say "if either side of the master will not bleed through, it is because the brake booster must be adjusted" do you mean that both sides of the master will continuously collect air from pedal usage?

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ok just like the clutch petal the master will freely flow fluid thru it's self if the lines are open,,, i was not meaning for you to pump the petal to bleed out the master,,but loosen all lines untill fluid is driping out the line fitting ,, you can use a couple shoop towels or a bundle of paper towels to soak up the fluid , if you use shop towels besure to place them where you will not later grab one and use it,, this can cause brake fluid to get where you do not want it

 

if fluid will not flow freely out of the master , it's posible the actuateing rod on the booster is too long,, the manual tells how to measure and adj this rod

 

again to clearify things has this car ever had good brakes and if so what did you do to loose them

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