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no rear brakes after rebuild
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cougar80
New User
Oct 6, 2008, 5:56 PM
Post #1 of 4
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no rear brakes after rebuild
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1999 Mercury Cougar; 2.5Lstandard; 138000 mi
I did a recent rebuild of rear brakes on this car including re-manufactured loaded calipers and new rotors. Properly bled system; no unusual problems. Now I have no function in brakes as they do not appreciably touch rotor when pedal is compressed. Parking brake works fine. I am stumped on this. I have driven 150 miles (carefully) with no rotor wear indicated. Any help is appreciated.
Note this is a non-ABS system.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 6, 2008, 8:09 PM
Post #2 of 4
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Re: no rear brakes after rebuild
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?? How did you bleed these? Was fluid assertively bleeding out if done by manual pedal push and bleed way?
Did they feel ok right away when finished bleeding?
Guess: Sometimes master cylinders aren't thrilled with being pushed to the end of their bore as when brake pedal goes to floor where master cyl hasn't been in a long time and may have crust and torn up seals at master cylinder. Just a guess. It may bleed ok but not really make the pressure to apply the brakes,
T
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Guest
Anonymous Poster
Oct 7, 2008, 3:09 PM
Post #3 of 4
(2735 views)
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Re: no rear brakes after rebuild
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Thanks Tom,
I bled them with a pressure bleeder at 15 psi (5 psi below max specified to be used). There was adequate flow at the calipers, but not excessive.
I was told that there was a TSA on this vehicle for a pressure conscious regulating valve on the rear brake line. Apparently the factory installed unit often times freezes up due to excessive corrosion, but typically not restricting fluid flow. Usually the condition is the reverse, it fails to restrict when heavy braking occurs, possible causing the vehicle to be unstable. I do not suspect this to be the cause but am unsure.
I am also unsure that the master cylinder is the problem as the front brakes are fine. I understand that they are separate from the rear. I hate to attack the master being unsure that it is the cause.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 7, 2008, 3:30 PM
Post #4 of 4
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Re: no rear brakes after rebuild
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Your pressure bleeder would go thru a faulty master cylinder! Master is actually two-in-one as you know. About all of them the part closest to the firewall/booster is for front brakes and usually sports a larger reservior and does when disc drum applications were the norm as disc brakes use brake fluid to compensate for the piston remaining further extended as the pads wear thru their life.
When bleeding brakes with the two person way you can see a brake apply force - even disc brakes flex some muscle in front of you when bleeding.
Guess if this was mine to do I'd bleed again with the two person way and watch for fluid which should near squirt to the other side left unchecked. If that was working then I question what the heck is causing NEW LOADED CALIPERS not to respond to brake fluid under pressure??
There's more going on in a rear caliper that also includes the parking brake mechanisms in it. I've never rebuilt one of those myself as for a long time now it's cheaper to buy pre done ones with exchange then all the seals, piston if needed etc., separately.
If pedal height and feel seems normal just sitting there and no braking is happening in the back then either a in line proportioning device is locking or caliper isn't budging at all. Piston would extend out and then you would need to screw (most turn to retract) the piston back in to be able to clear rotor if they extended out while not mounted or as when replacing pads only or for whatever reason you needed the clearance again to re-install the caliper.
Check as best you can that pressure gets back to them,
T
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