Stopping your car is critical, especially when you just had a bunch of work done and you don't want to rear-end someone. Or, maybe because you don't want to die. Simple things. Well, the GTO had a hard time stopping. I've known this for a while (years) and have really done nothing about it. But, now that I want to actually drive the car, the brakes needed some paying attention to. So how did I know there was an issue? What are the symptoms in an older, hydraulic-based, drum brake system that indicated your brakes may need bleeding?

Signs your brakes might need bleeding

Depressing the pedal with a low fluid level in the master cylinder reservoir or disconnecting any part of the hydraulic system permits air to enter the system. Air may also enter the system when brake shoes are replaced. Signs you might want to bleed the brakes...
  1. An idiot (warning) light comes on but only when the brake pedal is depressed nearly all the way down. In the case of a 1968 GTO (and maybe older A body, muscle cars and other GM makes from the 1960s), the warning is when the red "brake" light beneath the speedometer gauge turns on. This typically happens when you're low on brake fluid. Or, in my case, when you've got something going on with your brake system (like air in the lines).
  2. You have to depress the brake pedal all the way down to the floor before the car begins to slow.
  3. You have to pump the brake pedal repeatedly before the braking seems to respond normally.
  4. The brake pedal feels mushy.

I experienced all of the above issues with my 68 GTO. These are the tell tale signs that there is air trapped in the brake lines. It's bad if air gets trapped in your brake lines because it results in there being a lack of pressure in the braking system. Pressure is necessary in order to open and close the brake calipers. That's great, so now what do you do?

Tools you'll need to bleed your brakes

The method outlined in this article is the 2-person, pump and hold method of bleeding brake cylinders. Here's what you'll need...
  1. Mason jar or other container
  2. Clear brake bleeding tubing
  3. Brake bleeding wrench (J 21472)
  4. Appropriate brake fluid (DOT 3)
  5. Equipment needed to easily get to each wheel (floor jack, floor braces, lug nut wrench, etc)
  6. A buddy
Tip: I got a brake bleeding wrench from a brake tool tool set at Harbor Freight for $13.

How to bleed the brakes on a 1968 Pontiac GTO

  1. Remove the cap to the master cylinder and check to see if you're simply low on brake fluid. There are 2 sides that require filling. One side goes to the front brakes and the other the rear. If you're low, top off, seal the master cylinder and test the brakes again. Problem not solved? Continue reading...
  2. When bleeding the wheel cylinders, start with the front brakes (this is per the Pontiac shop manual) in this order: LF, RF, LR, RR. Jack the car up and take off the left wheel. This will make access to the bleed valve much easier.
  3. Fill the jar with enough clean brake fluid to fully submerge the end of the clear tubing
  4. Attach the tubing to the bleeder valve
  5. Have your buddy pump the brake pedal a few times and then hold the brake pedal down
  6. While the pedal is depressed, using the brake bleeding wrench, open the bleeder valve and keep in open until you see that no more air bubbles are coming out of the valve (visible in the clear tubing)
  7. Close the bleeder valve
  8. Release the brake pedal
  9. Repeat steps 5-8, for each wheel, multiple times per wheel, if necessary, in order to get all the air out of the brake lines
  10. Check both sides of the master cylinder reservoir to make sure there's enough fluid in each. You will have lost some brake fluid as a result of the bleeding.
Tip: Be careful when opening the master cylinder! Always clean any dirt around the reservoir cover first before removing the cover. You'll want to avoid getting any dust or dirt in the cylinder, as dirt can get in the lines and create a much larger mess.
1968 Pontiac GTO Service Manual