General 1981 Spider brakes "spongey"

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General 1981 Spider brakes "spongey"

wolfspider

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Recently, I purchased a 1981 Spider from someone who told me to be careful when braking, because the "brake vacuum pump" was going out. While driving it to my home, the brakes needed "pumped" to utilize them and while doing so, the engine acted like it wanted to die. It DIDN'T but came close. Could one of you "Spider mechanics" give me a clue as to what I should do to correct this? I haven't bought the manual yet but even when I DO it's always nice to be able to know what I'm looking up. Please help me...:(
 
Spongy brakes... not the booster.

A couple of things could be causing this:

A master cylinder thats pooched but first check that there is no air in the lines. Air will compress and give that oh s... feel to the brakes. When bleeding the rears, remember to jack it up on the axle, if you jack it up on the frame the compesator valve(behind rear pass. wheel) wont let fluid through and you'll be waisting your time. Make sure there is clean brake fluid in the res.
If this is done and still no firm brakes then likely the master cylinder.
Buy a new MC (about $30-40 I think) and bench bleed,that is fill the mc on the bench before install,to get all the air out,tilt forward tap,ect to get any bubbles out. If you have access to a pwer bleeder this helps hugely.
Repeat bleeding the brakes,shoud take a couple of hours at the most. If the booster is pooched then the brakes feel hard not soft.
More info at International auto parts tech section on bleeding brakes. Also important info on the clearance from the MC and the acorn nut on the booster. Have fun
 
Sounds like the master cylinder is on it's way out, even if you have bled the brakes, renewed the fluid and it still is spongey then you can pick one up pretty cheap. Use a proper bleeding kit as well, you'd be surprised when people say oh a piece of pipe and jar is fine, it's not always the case. Use the right tools and get it right first time.
 
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