Can't bleed air out of rear brakes

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You really don't want any of the brakes to lock up. Locked wheel= no control.
(Let's not get into the whole dry pavement skidding/ stopping distance thing. Most of the time you'll never lock up the brakes on bone dry level ground).
Gravity bleeding isn't foolproof. Believe it or not, air can still be trapped in the lines. It's a good way to start/ prime a brake line, but you can still have trapped air.
 
jos51700 said:
Ummm, if I'm reading this correctly, you're fundamentally wrong. You want the fronts to lock, and the rears to never lock.

Rears lock=spin.
Click to expand...

Its not spin its slide. Too easy to drag the rear tires while rolling steering controlling the fronts going downhill on dirt or gravel.
Of course I'm wrong. I've never driven on dirt roads. Just ignore me if you will.
My comments in other threads about master cylinders failing between out of the box and into the street were discounted too. From what I just read , It happened again.
I'm glad the original poster here did get his brakes working.
 
I'm having the same problem--replaced the power brake booster (vacuum leak). Bought the assembled with new master cylinder since, why not...

Bench bled the MC with scrapyard brake lines fed back into the reservoir.

2-person bled the system in proper order RR, LR, RF, LF and the pedal felt fine until I turned the car on...pedal to the floor.

Gravity bled the system with same results.

Jacked the car up while wife held the brakes. Fronts are locked and rears are free.

I haven't swapped to the old MC (which worked fine, btw) but that's my next step.

Thoughts?

1973 Swinger /6-225 front disc/rear drum
 
I'm having the same problem--replaced the power brake booster (vacuum leak). Bought the assembled with new master cylinder since, why not...

Bench bled the MC with scrapyard brake lines fed back into the reservoir.

2-person bled the system in proper order RR, LR, RF, LF and the pedal felt fine until I turned the car on...pedal to the floor.

Gravity bled the system with same results.

Jacked the car up while wife held the brakes. Fronts are locked and rears are free.

I haven't swapped to the old MC (which worked fine, btw) but that's my next step.

Thoughts?

1973 Swinger /6-225 front disc/rear drum
 
When the pedal felt fine after the first bleed, how far did it go towards the floor? It should have only been around 1/3 of the way down. If there was a lot more motion than that wiht the car not running, then the rears probably never beld and you were just getting the fronts to work against air in the rear half. That is what the 'wife holding the brakes' test indicates.

The pedal moving down with the power booster operating is normal. A common test for booster operation is to hold the pedal down with the engine stopped and then start the engine, and check that the pedal moves down some.
 
I agree about it not being bled properly, and, after much head scratching, I decided it was a bad rebuild and am searching for another one--autozone is out, o'reilly might be able to get one...but should I go for the stock remand unit or is there a better option?
 
I would personally only go for a NEW MC. NAPA's new Premium MC for your car is $66... (if I looked it up right).
 
Or,,you could just take the new one apart and see whats wrong with it. Theyre not real complicated devises. and chances are that its a simple fix. At least thats what I would do. Cause Im always curious how others screw up, so I can learn what not to do.
I learned to "take things apart" at a very young age. It frustrated my mom to no end, cause a lot of the time, whatever I "took apart" was not then reassembleable.Eventually I learned to plan ahead so as not to "break" stuff.
 
I returned the autozone cardone booster MC combo, and ordered a napa MC and a power brake exchange booster. I'll let you know how it goes. Should get here this week.
 
So...all of my problems pointed to a vacuum leak. Yet there were none to be found. EXCEPT it seems that I had a small leak inside the power brake booster...replaced with the expensive auto zone brake booster, a NEW master cylinder from Napa and, vavoom, she's all better now!

Runs like a charm. No more miss on the #6 cylinder, no more rough idle, and, hopefully, no more overheating under load...

W00t!
 
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