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> Bleeding master cylinder, How is this done
eyecolor
post Mar 18 2012, 06:26 PM
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After one of the longest brake rebuilds known to mankind (ask Eric Shea- I bought the parts 2 years ago), I just can't get the air out of the brake lines.
By chance someone asked if I had bleed the new master cylinder and I never knew it mattered.
I have searched the forum and have not found the procedure.
Before I before I drive it frightfully to a nearby mechanic, can anyone point me in the proper direction?

Thanks

George

Delaware
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ww914
post Mar 18 2012, 07:22 PM
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How did you bleed the system? The old way, having someone push on the brake while you open the valve? Or, did you use a pressure system where you can do it yourself? If you used the pressure system, did you start with the furthest brake away and move in toward the master cylinder? Also, check for leaks. Sometimes you have to bleed the brakes several times if the system is new. If you have new pads, they will feel squishy until they are beded.
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Prospectfarms
post Mar 18 2012, 09:16 PM
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Here's the opinion of an expert: http://www.914world.com/bbs2/index.php?s=&...t&p=1626189
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IronHillRestorations
post Mar 19 2012, 11:35 AM
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Here's how I bleed a 914 brake system, from my post back in Mar 05.

Remember the "Search" function is your friend!

Get a spare cap for the brake fluid reservoir.
Get a tire valve & stem.
Drill a hole in the center of the reservoir cap, the same size as the hole in a wheel (or measure the narrow part of the tire valve).
Pull the valve stem through the hole.
Remove the plastic screen in the reservoir.
Fill the brake reservoir completely, not to the fill line, all the way full to the bottom of the tube that holds the plastic screen.
Put on your new modified pressure bleeder cap.
Drain your air tank to 10 psi, for cheaper compressors setting the regulator at 10 psi may not work. If you put too much pressure in the system, you'll blow off the blue lines that connect the supply lines to the reservoir, or worse.
Take a clip on air chuck and clip it on your new pressure bleeder cap.
Bleed the brakes, starting at the furthest bleeder from the master cyl, and finish at the bleeder nearest the master cyl.
Bleeding sequence (RR-LR-RF-LF) EDITED FROM ORIGINAL POST
Pump the pedal hard about ten times and repeat the procedure.
Do not get brake fluid on painted surfaces it will ruin them.
If the pressure bleeder cap retains pressure, bleed it down before taking it off the reservoir.
This works very well, and makes it a one person job.
Replace brake fluid every two years.
Properly discard used brake fluid.
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eyecolor
post Mar 19 2012, 09:08 PM
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QUOTE(9146986 @ Mar 19 2012, 09:35 AM) *

Here's how I bleed a 914 brake system, from my post back in Mar 05.

Remember the "Search" function is your friend!

Get a spare cap for the brake fluid reservoir.
Get a tire valve & stem.
Drill a hole in the center of the reservoir cap, the same size as the hole in a wheel (or measure the narrow part of the tire valve).
Pull the valve stem through the hole.
Remove the plastic screen in the reservoir.
Fill the brake reservoir completely, not to the fill line, all the way full to the bottom of the tube that holds the plastic screen.
Put on your new modified pressure bleeder cap.
Drain your air tank to 10 psi, for cheaper compressors setting the regulator at 10 psi may not work. If you put too much pressure in the system, you'll blow off the blue lines that connect the supply lines to the reservoir, or worse.
Take a clip on air chuck and clip it on your new pressure bleeder cap.
Bleed the brakes, starting at the furthest bleeder from the master cyl, and finish at the bleeder nearest the master cyl.
Bleeding sequence (RR-LR-RF-LF) EDITED FROM ORIGINAL POST
Pump the pedal hard about ten times and repeat the procedure.
Do not get brake fluid on painted surfaces it will ruin them.
If the pressure bleeder cap retains pressure, bleed it down before taking it off the reservoir.
This works very well, and makes it a one person job.
Replace brake fluid every two years.
Properly discard used brake fluid.



Sounds amazing

And this will bleed the new master cylinder that was not done initially?

That was my search and I did try faithfully before writing.
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IronHillRestorations
post Mar 19 2012, 11:30 PM
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Yes, it works great. I don't pump the pedal until you get all the air out of the system. It's possible to invert a seal on the master cylinder if you actuate it dry.
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SLITS
post Mar 20 2012, 06:28 AM
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I just crack the fittings at the MC and let them drip for a few minutes. Works every time. I then proceed with pressure, vacuum or the old foot pumping method for the lines and calipers.
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