Master Cylinder Question?
Thread Starter
Racer
Joined: Sep 2004
Posts: 389
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From: Sayreville New Jersey
Master Cylinder Question?
I recently had new front calipers and master cylinder installed in my '78. Today the pedal was again feeling a little spongy and on hard braking the dash warning light came on. I checked for leaks at the wheels and couldn't find any by the wheels. Checked the MC and the front (closest to the nose) reservoir was a little low. Which reservoir is for the front brakes and which is for the rear? This could help track down my leak.
Thanx.
Thanx.
Tech Contributor
Joined: Aug 1999
Posts: 15,156
Likes: 3,965
From: Connecticut, USA
Originally Posted by 78Anni
I recently had new front calipers and master cylinder installed in my '78. Today the pedal was again feeling a little spongy and on hard braking the dash warning light came on. I checked for leaks at the wheels and couldn't find any by the wheels. Checked the MC and the front (closest to the nose) reservoir was a little low. Which reservoir is for the front brakes and which is for the rear? This could help track down my leak.
Thanx.
Thanx.
1- was the M/C bench bled,if not remove it and bench bleed it.
2-was the system bled, and what method was used?
Sounds like air in the system. Were the rotors checked for runout?
Gary
Burning Brakes
Joined: Aug 2004
Posts: 914
Likes: 0
From: Longview Texas
mine did the same thing, replaced both front calipers and master cylinder (bench bled per instructions) and had light on hard braking ....... went away for a while and now the light stays on yet fluid in m/c stays full ...... my thought is some air worked it's way to the proportioning valve and is stuck there ..... brakes work fine so that is a rainy day project ...... if I have learned nothing else, brakes on a vette require more than the average amount of work .......Robert
G'luck
G'luck
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
If the rotors are not almost dead flat (that is, no waves in the serface the pads ride on) they will "pump" the caliper pistons. This pumping action injects air into the calipers.
Have the rotors trued up.
Hope this helps.
BigBlockk
Later.....
Have the rotors trued up.
Hope this helps.
BigBlockk
Later.....
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
Originally Posted by BigBlockk
If the rotors are not almost dead flat (that is, no waves in the serface the pads ride on) they will "pump" the caliper pistons. This pumping action injects air into the calipers.
Advanced
Joined: Jan 2004
Posts: 65
Likes: 0
From: Muskego WI
You don't have to remove the master to bleed it out. If you still have it mounted in the vette, leave it in (bench bleed it in the car). Buy 12 inch brake line from the parts store and with a tube cutter, cut it in half. Disconnect the brake lines from the master. You want to bend the 2 six inch lines into almost a circle so that when you screw them into the master they will squirt back into each resivor. Fill each master 1/2 way full and then go into the car and SLOWLY depress the brake pedal to bleed the air out of the master. It is always a good idea to cover the fender with a towel incase of any splatter. Brake fluid will turn your paint white.
