Hello everyone I have a 2001 Honda Civic dx that I just bought as a commuting vehicle to replace my wrangler. The only problem with it is that the brakes slowly lock as you drive it. I was told it was a proportioning valve. But I find that hard to believe I was also told to adjust the brake booster piston or ram but I don’t see how to adjust it. Anyone experience anything similar? How can I fix it?
Sometimes a flexible brake hose can develop an internal tear that acts like a one-way valve. This stops one of the calipers from releasing quickly or at all. Repeated brake application slowly buids up the caliper pressure and causes brake drag. If the blockage is not complete, then the caliper pressure will slowly release. If it drags while you are driving, do this quick check. The dragging caliper will cause the rotor and hub to heat up more than normal. The internal tear is caused by techs using vise-grips to pinch the hose when removing the caliper.
Another possibility is that the small passageway in the master cylinder, which connects the working chamber within the master cylinder with the fluid reservoir above, is plugged. If that occurs, system pressure will not release when the brake pedal is released, and will gradually increase over time.
This will affect the brakes on all four wheels. If, on the other hand, only one brake caliper is failing to release, then the fault is most likely a failed flexible line, as @JohnCanon discusses in his answer.