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Author Topic: brake pedal is spongy  (Read 11331 times)

Offline nates79sbc

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brake pedal is spongy
« on: July 05, 2010, 04:18:52 pm »
Ok here we go the front axle has been completely rebuilt new everything rear main line and lines to wheel cylinders are new, new master cylinder it was bench bled then put on the truck and we bled the brakes at all four corners starting with the farthest from the master cylinder. pedal is rock solid with out the truck running, start it up and the pedal is soft and has alot of travel the truck will stop but its not right and im looking for ideas fronts all new back looks to be in good shape. im at a loss thanks for the information that may come to me.


oh the truck is  1979 chevy K10 with power brakes and disc in the front drums in the back. its got 350 th350 np 203. 10 bolt front and rear on 35s. thanks.
« Last Edit: July 05, 2010, 04:20:39 pm by nates79sbc »
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Offline zieg85

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Re: brake pedal is spongy
« Reply #1 on: July 05, 2010, 06:01:06 pm »
If everything is brand new, you still have air in the lines.... My $.02
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Offline mitch sonsteng

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Re: brake pedal is spongy
« Reply #2 on: July 05, 2010, 07:36:54 pm »
I had the same problem and i ended up using a vaccum bleeder, now the brakes work great.
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Offline 4x4orbust

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Re: brake pedal is spongy
« Reply #3 on: July 05, 2010, 08:56:36 pm »
just replaced my brake line on the front drivers this morning, gravity bled the brakes, took it for a spin, and it was the same as yours.


air in the lines.....
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Offline Irish_Alley

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Re: brake pedal is spongy
« Reply #4 on: July 06, 2010, 12:05:17 am »
pretty much everything they said could be the problem I would start with the cheapest being rebleed the lines with a brake bleeder. then if you didn’t have this problem before look at the master cylinder being bad you can get bad new parts from the store. are your brakes spongy for the first half then get rock hard on the second half with the engine on? If all else fails the booster should be last thing to be replaced since it was good before the problem started
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Offline Swims350

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Re: brake pedal is spongy
« Reply #5 on: July 06, 2010, 12:35:34 pm »
ok on the fronts did you replace the rubber flex lines? calipers? those can both cause it, the lines go bad over time, get soft and come apart inside or whatever they do. As for bench bleed, how long or how many times, some say it an take 75 times or more of pumping or like hours to do so.
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Offline nates79sbc

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Re: brake pedal is spongy
« Reply #6 on: July 18, 2010, 09:21:08 pm »
well guys thanks for the reply's and advice it ended up being the vacuum booster we believe it was from the brake fluid being boiled from the mess that brought on the total rebuild of the front axle. thanks for the help fellas.
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