Disc brakes were an emerging technology back when they were first introduced on Corvettes. Although disc brakes were first patented in 1902, materials that could truly make the technology possible didn’t exist until half a century later. In fact, the Corvette was among the first American cars to adopt disc brakes on all four wheels as standard equipment. However, there was a delete option in 1965 to revert back to drum brakes for those still leery of the technology.
Years later, these brakes can still confuse DIYers and mechanics alike. Not because of the now-not-so-new technology, but because how familiar we’ve become to disc brakes. The most common error that arises when bleeding these brakes is overlooking the extra bleeder screws on the rear calipers. There are two bleeder valves located in the front as we’ve come to expect, but there are four located in the rear. Two on each rear caliper. Most people never expect to look for those extra bleeder valves.
When bleeding these brakes it is important to bleed in the proper order to ensure air is removed from all the brake lines. Deviating from this order could lead to spongy breaks. The correct sequence for bleeding is: left rear inner and left rear outer, right rear inner and right rear outer, left front and right front.
The following instructions are in excerpt from the Corvette shop manual on how to bleed the brakes:
- Install the correct bleeding adapter to the master cylinder, Tool J-23518 [you may also use our deluxe pressure bleeder kit].
- Make sure the pressure tank is at least 1/3 full of Supreme # 11 brake fluid or its equivalent. The bleeder ball must be re-bled each time fluid is added.
- Charge the bleeder ball to between 20 and 25 psi (140 and 175 kPa).
- When ready to begin bleeding, connect hose to master cylinder bleeder adapter and open the tank valve.
- Bleed the brakes in the following sequence: left rear inner and left rear outer, right rear inner and right rear outer, left front and right front.
- With the proper size wrench over the bleeder valve, attach bleeder tube. The discharge end must hang submerged in a clean container partially filled with brake fluid.
- Open the bleeder valve at least 3/4 turn and allow flow to continue until no air is seen in the fluid.
- Close the bleed valve; be sure it seals.
- Repeat Steps 6-8 for the remaining bleeder valve (See Step 5 for sequence).
- Check the pedal feel for “sponginess” and repeat the entire procedure if necessary.
- Dispose of all removed brake fluid.
- Disconnect bleeder equipment from the brake bleeder adapter.
- Remove bleeder adapter. Wipe all areas dry if fluid was spilled during adapter removal.
- Fill master cylinder reservoir(s) to proper level and install master cylinder diaphragm and cover.