Mechanics

MY BRAKES ARE NOT WORKING PROPERLY

1993 Plymouth Colt • 116,000 miles

I changed the damaged brake hose, changed the brake fluid, and bled the brakes, yet they are still not working properly.
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Mason12
September 10, 2011.



How about a clue as to the symptoms? "Not working properly" can mean dozens of different things.
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Caradiodoc
Sep 10, 2011.
Well, I'll push them and they'll go straight down to the floor. There is little to no resistance. If they do stop them they don't gradually stop the tires, it's like I'm slamming them and my tires just stop moving altogether.

Tiny
Mason12
Sep 11, 2011.
It sounds like you may have a master cylinder leaking internally. There won't be the normal resistance to pedal movement, and when the secondary piston finally moves far enough, those two brakes apply quickly.

If you pedal-bled the brakes with a helper, and he pushed the pedal all the way to the floor, that's when the master cylinder gets damaged. A lot of crud and corrosion builds up in the bottom halves of the bores where the pistons don't normally travel. When you push it all the way during bleeding, the lip seals run over that corrosion and get torn. That's where the internal leakage comes from. The additional clue is you're not losing any fluid from the reservoir as you would with a leaking line or hose.

It's okay to push the pedal all the way down to the floor if the master cylinder is new and doesn't have that corrosion yet, but most mechanics know to never push it more than half way if it's more than a few years old.

On the very slim chance there's still air in the line going to the hose you replaced, assuming it's a front caliper, use a large flat blade screwdriver as a pry bar to force the piston back into the caliper. That will push a lot of fluid up to the reservoir and any air with it. Then, if you repeatedly stroke the pedal half way to the floor, you should see the piston move back out until the pads contact the rotor. If the piston doesn't move with each pedal stroke, you'll have proof the master cylinder must be replaced.

Caradiodoc
Sep 11, 2011.

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