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Grabbing Brakes |
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Grem70
AMC Fan Joined: Jun/20/2012 Location: Wisconsin Status: Offline Points: 11 |
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Posted: Jun/07/2015 at 11:17pm |
Hope someone can help/advice on my '70 Gremlin brake problem.(power brakes-shoes)
Brakes grab "violently". I bought this Grem about 8 years ago with this problem. Seller said previous owner had same problem. Long story/short.....I think finally I found problem. Too much vacuum. I put clamp on vacuum line leading to booster and when I tighten clamp, just right, to restrict vacuum, brakes work normally-no grab-99% improvement. I'm thinking booster is faulty. My question is....can I get booster repaired? or where can I buy a new master cylinder/booster? Or any other solution? I suspect other cars must have used same booster/cylinder combo. (For example I installed a '77 Plymouth Volare booster combo on my '59 Plymouth and it fits and works perfectly) Any help appreciated. |
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Grem70
AMC Fan Joined: Jun/20/2012 Location: Wisconsin Status: Offline Points: 11 |
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Just did some checking and found O'Reillys and Autozone have Boosters for '70 Gremlins.
So anyway, if anybody has grabbing brakes, check out your vacuum. I've been screwing around with this off and on for a loooong time, and a local stock car driver suggested clamping the vacuum line as a test and he was right. |
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farna
Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19611 |
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You can get a new check valve for the booster. That might be the whole problem. The check valve keeps the booster from leaking vacuum, but it also has a restriction in it to keep it from pulling too much. I'm surprised you don't have some idling problems if it has that little restriction on it though.
If it was converted to power brakes they may have a big car booster on it, or a dual diaphragm designed for power disc brakes. That's assuming you have drums on front. Could also be the wrong master cylinder, or the push-rod between booster and master is too long. The originals have an adjustment. |
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Frank Swygert
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ramblinrev
Moderator Group Joined: Dec/28/2008 Location: Wisconsin Status: Offline Points: 11470 |
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Drum brakes (power or manual) can also grab if someone accidentally switched the primary and secondary shoes (ask me how I know!)
That would be an easy-and easily overlooked-fix. |
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74 Hornet Hatchback X twins (since 1977)
62 American Convertible (still worth the $50 I spent in 1973!) AMCRC #513, AMO #384 70 AMX 360 4-speed (since 1981) |
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Cornelius Rambler
AMC Nut Joined: May/13/2013 Location: Escondido CA Status: Offline Points: 252 |
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I'm not sure if this helps or not, but does anyone know if the pedal is different between power brake and non-power brake AMC's in certain years?
The pedals in 1967-1973 Mustangs and Cougars, for example, were different lengths because the pivot point on the brake support was different to reduce the leverage on power brake cars in order to counteract the problem that I believe that you are describing. If the same thing was true with various AMC models and a PO added a booster without changing the pedal, that may account for the "grabbing."
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george w
Supporter of TheAMCForum Joined: Jan/27/2013 Location: New Jersey Status: Offline Points: 2899 |
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X2 on the primary and secondary shoe reversal. Primary shoe is toward the front of the car and has the shorter lining. This applies to all 4 wheels.
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Long time AMC fan. Ambassador 343, AMX 390, Hornet 360, Spirit 304 and Javelin 390. All but javelin bought new.
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gwryder
Supporter of TheAMCForum Joined: Jun/30/2009 Location: Michigan Status: Offline Points: 710 |
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Sounds interesting. How? John |
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John
70 AMX |
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