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Front brakes stay engaged |
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72_AMX
AMC Apprentice Joined: Jul/16/2019 Location: Somerville, Al Status: Offline Points: 69 |
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Posted: Jul/26/2020 at 6:36am |
Morning. I need some assistance The Front disc brakes on my 72 AMX staged slightly engaged. So far I have replaced the master cylinder both front rotors, calipers, pads and brake hoses. Any ideas or suggestions on what could be wrong. When the car is moving I can put it in neutral and the car will come to a stop and stay in place even on a upward incline. the petal has almost to travel to it and is stiff. Thanks
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6768rogues
AMC Addicted Joined: Jul/03/2007 Location: United States Status: Offline Points: 6241 |
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Are you sure you have a disc brake master and not one for drum brakes?
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Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6910 |
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Disk brakes need the residual check valve removed at the master cylinder just inside were the disk brake supply line attaches to the master.
Many masters will ship with residual check valves installed regardless of intended use. I'd be check this first.
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purple72Gremlin
AMC Addicted Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16614 |
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And or did you make sure the slides are free?
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72_AMX
AMC Apprentice Joined: Jul/16/2019 Location: Somerville, Al Status: Offline Points: 69 |
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Thanks for the info. I will check on the check valve and slides. I thought the slides where free but will check again. I did not know about the check valve. Thanks again for the info.
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mramc
AMC Addicted Joined: Jul/12/2007 Location: United States Status: Offline Points: 3223 |
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Also check the front brakes hoses, some times they collapse internally . You may not see it, but if your brakes hoses have not been changed in 50 years , time to do so. They are not good forever. LRDaum
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LRDaum
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72_AMX
AMC Apprentice Joined: Jul/16/2019 Location: Somerville, Al Status: Offline Points: 69 |
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Thanks will do
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being Alive is not the same as Living
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Fluffy73
AMC Addicted Joined: Nov/21/2007 Location: Castlegar, BC Status: Offline Points: 3059 |
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Check to make sure you were given the correct master cylinder. I chased the same issue for years. Turns out there is a master cylinder available that looks identical to ours but has the reservoirs swapped. Make sure yours has the small reservoir to the front.
For years, my car had issue with the fronts dragging and under hard braking the rears would lock up. After I changed out a broken axle, I went to bleed the brakes and opening the rear circuit, the large reservoir in the master began to drain. Wrong Circuit! |
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Twisted70amx
AMC Apprentice Joined: Feb/04/2018 Location: Ontario Status: Offline Points: 63 |
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Not sure what your history is with the car but if it wasnt checked when replacing the MS the brake booster pushrod length might be too long. That'll cause a firm pedal and keep the brakes engaged. There's a tool to check it but it you go to push your MS onto the booster and there a small gap before you apply pressure or tighten the nuts I'd say it's likely your cause. The tool checks with it disassembled. Good videos on YT on how to set it up.
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72_AMX
AMC Apprentice Joined: Jul/16/2019 Location: Somerville, Al Status: Offline Points: 69 |
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Thanks for the follow-up. I did check the Master Cylinder and the small reservoir is in the front. I talked to the mechanic who installed the MC and asked him about the push rod. He stated that there was not a problem that he could tell when he installed it. I still have the original MC and will send it off to be rebuilt just in case. We are going to replace the brake hoses and see if that works. Any ideas on if the hoses are bad could the interior pieces of the hose contaminate the channels in the calipers? Any suggestions on a good brake MC and Caliper rebuilder.
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