master cylinder?

[Dean W]

My 2000 grand am(3.4 l engine) still has air in the brake lines after bleeding the brakes and topping up more than a llitre of brake fluid as I blead them. Could this be a faulty master cylinder. It was suggested that the master cylinder might leak air but not brake fluid. Anty one heard of this?

[xeroinfinity]

if the seal in between the booster and MS is bad it can certainly leak air in. Also the vacum line can leak air if the seals bad or broken.

Are you bleeding them with the key on?
The key should be on.
Sometimes you may need to pull a vacum at the MS under the hood. Thiers a special tool that draws the air up that way, expensive though. And pulling a vacum at the bleeders could also help.

With ABS you can hav problems with air staying in the ABS Hydraulic modulator or proportioning vavle. The ABS Modulator and proportioning valve are under the battery. The Hydraulic Mod has bleeders, you bleed the rear first, then the front.
To bleed the proportioning vavle, it needs done at the lines, starting with the bottom one then the top.

When you bled the brakes, did you do them in this sequence?
Right rear, Left frnt, Left rear, Right frnt, for best results.