i think my master cylinder is shot?

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ef8340

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another problem has showed up on the dart the brake pedal isnt firm anymore kinda squishy and the master cylinder is leaking around the cover it also has a vibration when stopping at highway speeds any ideas
kelsey/hayes 4 piston disc brakes up front 10" drum on back
Terry
 
If they're squishy, it sounds like you have air in the line. You will need to bleed them, but check to see that your rear wheel cylinders aren't bad. To do this, peel up the rubber grommet on the ends, and if there is fluid inside, they are bad. If it is dry inside, they are good.

Is the master a remanned? If so, it most likely uses the poly urethane (or whatever) seal, and those are crap. If you can find one from something older that uses a rubber seal, grab it. Also when I bought mine for front disc rear drum, the lid was warped just a little, hardly noticable, but enough to leak.

As for a vibration at highway speeds, since our cars don't have ABS, I would assume a warped rotor, but someone should chime in on this one.
 
Oh another thing, each time the master leaks, are you adding more fluid to it to top it up? Because if it leaked enough that you got air in the line, the next time you added fluid to top it up, you would be trapping the air inside the line, resulting in squishy brakes.
 
this weekend im gonna bleed the brakes and check the rear wheel cylinders the master cylinder is a reman unit from advanced so far most of the stuff that i get from advaced is crap really startin to not like advanced auto
thanks Mike
Terry
 
I bought my remanned master cylinder from Lordco Auto Parts, a company based here in BC, and the master itself works fine, just the lid was warped, and the crappy poly whatever seal leaked. So I found an identical one on a Cordoba and used it (it had the rubber seal instead and was straight). Since then, no leaks.
 
70DartMike said:
As for a vibration at highway speeds, since our cars don't have ABS, I would assume a warped rotor, but someone should chime in on this one.
Click to expand...

If the vibration occurs only when the brakes are applied, it probably is a warped rotor. The brake pedal will pulse almost like an ABS system will.

If the vibration is not felt through the pedal, but through the steering wheel, it is usually an alignment issue. It could as simple as re-aligning the front end or as complicated as needing to replace bushings and ball joints. Other possibilities are worn wheel bearings or loose wheel/retaining nut.
 
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