1977 Brake Bleed thoughts

[xkeots]

Looking for yeas and nays on bleeding the 77 Corvette system. When I replaced all calipers I did old school, pumping pedal and opening the bleed nipple. Just replaced the master and vacuum, the pedal is starting out lower than what was in the car. I bled the same way as always but I don't like the pedal height. Has anyone here had good results with gravity bleeding the system? Gravity or manual with 2 people on the 77?.
Thanks
Jack
1977 L-82

 

[dougelam]

Did you bench bleed the master cylinder first?

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[toobroketoretire]

Gravity Bleeding Brakes

Looking for yeas and nays on bleeding the 77 Corvette system. When I replaced all calipers I did old school, pumping pedal and opening the bleed nipple. Just replaced the master and vacuum, the pedal is starting out lower than what was in the car. I bled the same way as always but I don't like the pedal height. Has anyone here had good results with gravity bleeding the system? Gravity or manual with 2 people on the 77?.
Thanks
Jack
1977 L-82

First of all if you replaced the power brake booster and didn't adjust the push rod to the exact same length as your old booster your pedal height WILL be different. But as long as the height is within reason it's not a problem and you'll get used to it. To gravity bleed brakes you must fill the master cylinder's reservoirs and keep them full during the bleeding process And the lid MUST remain off during the bleeding). With the reservoirs full start by opening the right rear outside bleeder and keep it wide open until you get a steady drip drip drip drip drip drip drip drip drip. Torque the bleeder screw to 90 lb/in then open the inside bleeder and wait until it is steadily dripping. Then repeat the process on the left rear bleeders then move to the front right bleeder then the left front bleeder.

Is your master cylinder push rod the adjustable type with the knurled body and 5/16" hex end? If so that push rod must be short enough to ensure the master cylinder pistons can fully retract clear back to the snap ring. If that push rod is too long and holding the piston foreword enough to cover the fill hole in the bottom of the reservoir it'll never be able to be bled. If your master cylinder was bench bled first it could take up to 30 minutes in cold weather to be able to get the steady drip drip drip you want because the brake fluid does get thicker when it's cold.

 

[SVO]

Whenever I have gravity bled the brakes, I pull the pads out, and starting at the back, open up the bleeders on both the calipers and let it go until there is clear fluid coming out of the bleeders. Once I get clear fluid, close that bleeder and wait on the other half to flow clear. Then repeat for the front. Then follow that with cleaning brake fluid off the calipers, re-install the pads and pump the brakes and bleed each half, starting again at the rear.

I have also used a hand vacuum pump to pull fluid from each half calipers, again starting with at the right rear, then left rear, then right front and left front. You can get a vacuum brake bleeding bottle & a hand pump from the local auto parts place.

Last brake job I used one of the Phoneix (sp?) fluid injectors, which worked quite well. The fluid injector works by pushing fluid from the caliper back to the master cylinder. The advantage of this is you are pushing air up hill rather than down hill. With the injector, you have to monitor the fluid level in the master to avoid overfilling the master. Phoneix fluid injector also works quite well for hydraulic clutches, should you ever have that need.