I have a 1992 Toyota Corolla. In the winter sometimes the brake pedal is hard as a rock when the car is cold (overnight or after work) and the brakes do not work at all until I push on the pedal with two feet! After that, they work fine. Also, I can hear the pads rubbing on the rotors. It’s like the calipers are not retreating fully after application. I’ve replaced both the rotors and the pads. I’ve also taken the calipers out and made sure they are moving. They are. I can easily push them in and out with the appropriate pressure. What’s my problem?
You might want to check the vacuum hose to the brake booster for internal moisture. If there’s any moisture in this hose and it freezes, it will prevent vacuum from reaching the brake booster which will cause a hard brake pedal.
Also, unless you know that the brake fluid was changed in the last 3 or 4 years, you should have the brake fluid changed. Because of its hygroscopic nature, brake fluid absorbs moisture from the air and this can eventually lead to a signficant amount of water in the brake fluid. This water can freeze and cause problems.
Additionally, when the brakes are used heavily–such as when driving downhill on a steep grade–the water in the fluid can actually boil and this will result in NO braking ability just when you need it the most.
I think that changing the brake fluid is one of the most ignored maintenance items on cars, and it has the potential to be very dangerous.
How much fluid do you need to bleed from each wheel to completely replace the fluid in the system?
Also, would moisture in the lines keep the calipers from retreating? Thanks!