talk about general wheeling tech(i.e wheels, axles,tires also for tech articals )
By adamK1500
Hey guys, it's been awhile since I've been on here but I have a question about brakes.
I just installed a new master cylinder and rear wheel cylinders in my Mazda pickup. The brakes worked awesome for about a day and now the brake pedal goes straight to the floor like there's no fluid in it. I checked the reservoir and it was full. I went to bleed the rear brakes and no fluid came out. This makes me think I have a clogged brake line, but I don't understand why that would make my pedal so squishy.

Any ideas?
By Ryan283
Sounds like a bad master cylinder, which is weird because you just changed it.
Sometimes a bad one will allow fluid to bypass and not create pressure.
It's odd because the fluid isn't leaking anywhere,,,,,it's just not building pressure. It's getting bypassed inside of the master cylinder.

OR, you may still have a huge pocket of air in the lines. Try bleeding the lines, then bleed them again. Then bleed them again. then bleed them again.

OR, are the rear pads shot? Maybe the disk cylinders are fine,,,,but the pads are exhausted?
By adamK1500
I wasn't completely confident about bench bleeding the master cylinder so I had thought that that could be the problem but the brakes worked great for the first day. It was a pretty sudden change from great brakes to no brakes.
The shoes are new. I replaced them with the cylinders.
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By Weasel
how are the front brakes? I would check for an air leak, not unheard of the have a bad 'new' M/C given the high quality of replacement parts now a days. I only ask about the front as you could not have rear brakes and not notice so much, but you will notice no or weak front brakes, they provide most of your stopping force.
By adamK1500
It feels like I have almost no brakes, the front brakes bleed fine though. I'm thinking about trying to get the master cylinder replaced under warranty and going from there.
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By axleater
if you can get a vacuum bleeder and suck the fluid from the furthest bleeder from the master cyl and then go from there. I would guess new master didn't get bled enough before intall.
By adamK1500
1984, no ABS. I'm gonna rent a pressure bleeder and see if I can get any fluid through the system.
By adamK1500
Just tried the pressure brake bleeder. I wasn't able to get anything out. Anything else i should try with the tool before i return it?
By sicbronconut
I'd start breaking lines open from the rear to the master cylinder to see if fluid comes out with the pedal applied. HTH Steve
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