all four caliper freeze up.

1986 635 csi. car has two new front calipers, new pads all round, drilled & slotted rotors, new steel braided brake lines & two year old abs booster. 133,000 miles, the car when you frirst start you can push with one hand on flat ground. drive it three miles and you could fry chicken on all four calipers rotors and hubs. please help. the process of elimination is costly.

Your problem, for this old thread

Is the brake master cylinder shaft and the end plug that surrounds the shaft that goes to the brake booster.
There is a plug at the end of the M/C made of a fiber material (phenolic) that has failed and it swells and squeezes the shaft when the underhood temperature increases,
and the M/C fails to release.
Thus the brakes are locked on until the temperature goes back down.
I rebuild BMW Audi and Porsche parts

Best,

Jay
M6