Many GTOs seem to arrive in the US with discolored brake fluid and air in the brake lines. It may be poor procedures at the factory or the long ocean cruise and transition time on the docks waiting to clear Customs. Regardless of the reason, you can’t go wrong with bleeding your brakes and flushing out the original brake fluid. This should be the
first mod any new GTO owner does. Make sure you use a quality DOT 4 fluid with a high temperature rating so it can stand up to the heat generated from high-speed braking. Many GTO owners have found synthetic brake fluid from Valvoline to perform well and be readily available from local automotive stores at a reasonable cost. Here is a link with additional brake fluid performance details.
http://brickboard.com/FAQ/700-900/Br...Comparison.htm
You can tell there is air in your brake lines if you apply the brakes, release them, and then quickly reapply them and the pedal feels firmer and often stops further off the floor with the same pressure. It doesn’t take but a tiny bubble in your lines to impact pedal firmness. It is not unusual for some GTO owners to bleed two or three times before they get all the air out of the system that came from the factory. Some new owners experience their GTO’s spongy brakes and decide they need to buy an upgrade kit. When they install the upgrade and bleed the brake lines as part of the upgrade process, they think the improved brake feel and performance came from the upgrade - they should have bleed their brakes first! The 05 OEM brakes have a very solid pedal, even without adding stainless steel brake lines, if there is no air in the brake lines!! The 04 OEM brakes are not as firm because the caliper is not as stiff and will flex during hard brake applications allowing the pedal to continue to the floor with increased brake pedal pressure.
As an alternative to power bleeders or 2-man brake pumping, try gravity bleeding. Introduced to me via the GTO forums, gravity bleeding is a simple, single-man operation. Just connect one end of your drain line to the bleed screw, deposit the other end into your waste container, crack open the bleeder screw a turn, and left gravity do the work. Return every 5 to 10 minutes to top off the master cylinder reservoir so it does not drain dry and let air into the lines. As always, bleed from the furthest caliper to the nearest, e.g., right rear, left rear, right front, and left front. It may be hard to tell when all the “old” fluid has been flushed. I make sure the equivalent of the reservoir’s volume goes through each caliper. Buy 2 quarts to be safe and ensure you don't have to run back out to buy more in the middle of the job. I needed to use the second bottle because I had to bleed twice to get all the air out. Remember to dispose of the used brake fluid in an environmentally safe way.
There are no special tools or procedures to bleed your brake lines because the GTO has anti-lock brakes. The anti-lock brake unit does not enter the system unless it is activated. Thus, you could find yourself with a firm pedal, then after a hard brake application where the anti-lock brakes activate, you could have air back in your lines again. Just bleed your brakes again to remove the air bubble. If you still suspect air in your anti-lock braking unit, you have two options. You can take your GTO out and activate the anti-lock system on purpose and see if you pedal feel changes or take it to a shop that has the equipment to activate the anti-lock unit during a bleed operation. It is not common to have problems with air in the anti-lock brake units.
While you are bleeding the brakes as your first mod on your new GTO, consider installing a quality set of Corvette C5 or C6 brake pads for added performance.
