Yes there are two on each caliper in the back.
brakes are a pain. before you go and re-invent the wheel try bleeding it out, could have air still
1978 Brake problems
Thread Starter
Intermediate
Joined: Jan 2013
Posts: 38
Likes: 0
1978 Brake problems
I installed a new master cylinder and all four calipers (OME), used a Mityvac to bleed the brakes. Had a full pedal, then took it for a test drive. Brakes worked great until I had driven about 25 miles then the pedal went to the floor----NO BRAKES! I'm glad it was a four way stop and no traffic. Anyway the master cylinder was full of fluid, no leakage from any caliper. After sitting for thirty minutes with the hood up it had about 1/4 pedal and would stop the car. It took a while to get home driving like an old man (I'm only 66) with one hand on the parking brake. What did I do wrong? This car has to be female, it seems to know when I have spare cash to spend.
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,754
From: Charlotte NC
Did you bench bleed the master cylinder BEFORE you installed it??? Even when I bench bleed a master cylinder it takes some time to get all of the air our and no bubbles showing up. I can have 15-30 minutes in bench bleeding a master cylinder. I do it slowly and only depress the piston one inch.
I normally use a pressure bleeder when doing brakes. You can also have air in the system. I have encountered an issue many times when I am installing a complete system...and using my pressure bleeder and bench bleeding the master cylinder...that even when I am bleeding the system out with pressure...and vibrating the frame to aid in releasing any bubbles ( microscopic ones) that cling to the inside of the lines and caliper bores...that sometimes I need to re-bleed the system again a second time and find that I will get very small bubbles that come out....due to the very small bubbles collect in time and make a larger bubble.
DUB
I normally use a pressure bleeder when doing brakes. You can also have air in the system. I have encountered an issue many times when I am installing a complete system...and using my pressure bleeder and bench bleeding the master cylinder...that even when I am bleeding the system out with pressure...and vibrating the frame to aid in releasing any bubbles ( microscopic ones) that cling to the inside of the lines and caliper bores...that sometimes I need to re-bleed the system again a second time and find that I will get very small bubbles that come out....due to the very small bubbles collect in time and make a larger bubble.
DUB
Thread Starter
Intermediate
Joined: Jan 2013
Posts: 38
Likes: 0
Yes I did bench bleed the master cylinder. Then bleeding each caliper, left rear first by the book. Went through 2 quarts of brake fluid bleeding the calipers, I'll try again tomorrow.
Could my problem be the vacuum booster?
Could my problem be the vacuum booster?
Melting Slicks
Joined: Mar 2007
Posts: 2,520
Likes: 11
From: Hinckley OH
Two possibilities come to mind.
Runout causing the pads to pulsate and suck air past the lip seals in the caliper. If this is the case you should get some air out of the bleeders when you bleed the brakes.
Brake fluid can boil if a line is too close to anything hot. If you have a full pedal with the engine running after it cools down, this might be the cause.
Did you bleed both bleeder screws on the rear calipers?
No, a failed vacuum booster will cause a hard pedal and longer stopping distances.
Runout causing the pads to pulsate and suck air past the lip seals in the caliper. If this is the case you should get some air out of the bleeders when you bleed the brakes.
Brake fluid can boil if a line is too close to anything hot. If you have a full pedal with the engine running after it cools down, this might be the cause.
Did you bleed both bleeder screws on the rear calipers?
No, a failed vacuum booster will cause a hard pedal and longer stopping distances.
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