71 Master Cylinder problems
06-18-2011, 02:46 PM
#1
1st Gear Member
Thread Starter
Join Date: Mar 2006
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Posts: 74
71 Master Cylinder problems
71 mustang coupe w/ 351c 4v w/ power brakes
Recently had the master cylinder replaced b/c it was leaking.
A NEW Master cylinder from Napa. Part #M1929
At the same time the rear brakes & wheel cylinders were replaced.
At first the pedal was weak and pulled to the right.
I replaced the calipers and pads a couple of days later and bled the brakes again.
Now you only get a good pedal by pumping it two or three times.
Took it back to the shop. They bled the brakes, and pressure bled them from the wheel cylinders and calipers up to the master.
Still the same.
Bad Master cylinder?
Recently had the master cylinder replaced b/c it was leaking.
A NEW Master cylinder from Napa. Part #M1929
At the same time the rear brakes & wheel cylinders were replaced.
At first the pedal was weak and pulled to the right.
I replaced the calipers and pads a couple of days later and bled the brakes again.
Now you only get a good pedal by pumping it two or three times.
Took it back to the shop. They bled the brakes, and pressure bled them from the wheel cylinders and calipers up to the master.
Still the same.
Bad Master cylinder?
06-18-2011, 08:35 PM
#2
1st Gear Member
Join Date: Nov 2006
Location:
Posts: 98
On my 71 the push rod that goes into the master cylinder has an adjustment screw on the end. You may want to check to see if the length is okay. Too short will cause a problem, not sure how it will react. Too long will cause a problem. I believe it will damage the master cylinder.
I changed mine a couple years ago. I lengthened the push rod just a little.
I guess it could be a bad porportioning valve. Don't believe they are serviceable.
I changed mine a couple years ago. I lengthened the push rod just a little.
I guess it could be a bad porportioning valve. Don't believe they are serviceable.
06-22-2011, 09:14 PM
#3
2nd Gear Member
Join Date: Oct 2008
Location: Illinois
Posts: 251
71 mustang coupe w/ 351c 4v w/ power brakes
Recently had the master cylinder replaced b/c it was leaking.
A NEW Master cylinder from Napa. Part #M1929
At the same time the rear brakes & wheel cylinders were replaced.
At first the pedal was weak and pulled to the right.
I replaced the calipers and pads a couple of days later and bled the brakes again.
Now you only get a good pedal by pumping it two or three times.
Took it back to the shop. They bled the brakes, and pressure bled them from the wheel cylinders and calipers up to the master.
Still the same.
Bad Master cylinder?
Recently had the master cylinder replaced b/c it was leaking.
A NEW Master cylinder from Napa. Part #M1929
At the same time the rear brakes & wheel cylinders were replaced.
At first the pedal was weak and pulled to the right.
I replaced the calipers and pads a couple of days later and bled the brakes again.
Now you only get a good pedal by pumping it two or three times.
Took it back to the shop. They bled the brakes, and pressure bled them from the wheel cylinders and calipers up to the master.
Still the same.
Bad Master cylinder?
Very obvious the rear brakes are not adjust properly, or not installed correctly.
The front brakes are really none adjustable, No Residuals to cause a problem. On the rears, No residual means you are pushing fluid all the way to the back each time. With poorly adjusted brakes, then the problem becomes magnified.
Holly Goodness!!!
Dan @ Chockostang
06-25-2011, 12:49 PM
#4
1st Gear Member
Thread Starter
Join Date: Mar 2006
Location:
Posts: 74
I had the shop work on it again. They set the timing properly b/c it started pinging after they messed with it. Better now.
They back bled the brakes, and bled the brakes to no avail. Checked adj on rear brakes, they were good.
Eventually we changed the master and sudden improvement... but not completely.
They checked the adj rod while installing the master by "feel", no actual measurement.
Still the pedal travels farther the first time you press it to engage than subsequent times.
Seems exaggerated at idle, but only slightly.
Rod need adjustment or could it be power booster?
How does one test the power booster?
Thanks!
They back bled the brakes, and bled the brakes to no avail. Checked adj on rear brakes, they were good.
Eventually we changed the master and sudden improvement... but not completely.
They checked the adj rod while installing the master by "feel", no actual measurement.
Still the pedal travels farther the first time you press it to engage than subsequent times.
Seems exaggerated at idle, but only slightly.
Rod need adjustment or could it be power booster?
How does one test the power booster?
Thanks!
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