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Master cylinder troubles... I think


rubenyc

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So I'm driving my 1990 Lumina 3.1 home today. When I brake slightly for a traffic light, I hear a sort of crunchy sound and my pedal goes halfway to the floor. I figure *&$*#, I blew a brake line, so I immediately look in my rear view mirror for signs of fluid on the tarmac, but there's nothing. I pull over and check under the car - nothing is leaking as far as I can see.

 

It's like half a mile to my house so I'm driving it very carefully, noticing that the brakes squeal slightly as the car rolls along. I'm not sure if all of them do it, or just one wheel. Meanwhile its stopping power gets less and the pedal sinks deeper. Pumping the pedal didn't seem to help, but then I didn't try pumping more than three times.

 

When I park the car I check my master cylinder - it seems to be at the same level as before. Check under the car again - still no sign of leaks. Because I've been driving around with a rattly inside brake pad on my left rear wheel (some kind of spring needs to be replaced, I ordered the part) I think maybe this has something to do with it, so I take my wheel off only to find that everything's still the way it was (at least it seems to be).

 

We also just bled the brakes on this thing a few weeks ago - it had some air in it before. Since then, it's braked fine 98% of the time - the other 2% the pedal would sink just a little bit, like it was hitting air again, then return back to normal quickly.

 

I was reading this thread, which points to the master cylinder being the problem. Would that explain the brake squealing though? Also, do you guys recommend a new master cylinder or a rebuild?

 

Thanks

-ruben

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No, I haven't noticed the idle changing. I'll try to look behind the cylinder to see if it's leaking. But if the braking power is lost like this and it's due to a leak, shouldn't I lose a lot of fluid? The level in the master cylinder doesn't seem to have dropped at all...

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No, I haven't noticed the idle changing. I'll try to look behind the cylinder to see if it's leaking. But if the braking power is lost like this and it's due to a leak, shouldn't I lose a lot of fluid? The level in the master cylinder doesn't seem to have dropped at all...

 

Honestly I don't know. take the brake booster hose off and put the oil dipstick in there and see if you get any fluid.

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it sounds like the piston in the master cylinder itself is cracked, and is not actually building enough pressure in the lines. That would explain the crunch, and lack of breaking power, and the non-dropping fluid level ...

 

The squeeking noise is probably unrelated to the M/C issue.

 

--Dave.[br]Posted on: March 30, 2006, 10:57:24 AM_________________________________________________any update on this?

 

--Dave.

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  • 3 weeks later...

on occasion I have seen cars throw brake pads.... sometime entirely, or just the friction material shears off the backing. check all four wheels?

 

on my rear of my 95 cs , it soundled like gravel for a while, I pulled to wheel off to discover that the friction material had sheared from the backing, but it was caged by the bracket and was knocking and making noise!

 

just my thought.

 

 

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