This has happened to me on other cars - Camaros and such, and always with the typical GM 10.5" single piston floating caliper disc brakes that GM has used on many many different cars over the years. I never figured out why on other cars and now I'm in the same situation again.... and out of ideas.

When cold the brakes stop stright as an arrow. Make a few firm stops and get some heat in the brakes and it'll start to pull HARD to the left. It pulls hard at the wheel, too- not just like the car goes left but the wheel is neutral. It's definitely a problem with the FRONT brakes- if you keep stepping through it'll lock the front left long before the front right. Let the brakes cool and it'll stop straight as an arrow again.

I have replaced EVERYTHING in the front brakes- rotors, calipers, brake hoses, adjusted the wheel bearings, bled gallons of fluid through the brakes, etc. Rear brakes work fine- I checked them, too.

I'm outta ideas. Since this has only happened to me with the 10.5" single piston floating caliper disc brakes on GM cars I'm wondering if this isn't something somebody else may have encounterd. Any help?

 

When you said you replaced the brake lines, did you replace the entire brake line from the master cylinder to the caliper?