گرفتگی یا تنگی مسیر هیدرولیک ترمز

A brake circuit that will not let fluid move freely — most often inside the ABS modulator, where the passages are a fraction of a millimetre across.

The symptom that matters is a brake slow to release rather than slow to apply. Pressure gets to the wheel and then cannot get out, so the brake drags: that corner heats up, the car pulls to one side, and the pad and disc on that wheel wear far faster than their opposite numbers.

Old brake fluid is the usual reason, because the corrosion and debris it carries end up wherever the passages are narrowest.

A collapsed flexible hose imitates it exactly and is much cheaper. The inner lining can lift and act as a one-way valve — fluid in, none out. The test that separates them is simple: crack the bleed nipple at the dragging caliper. If the brake releases instantly, the restriction is upstream in the hose or modulator, and the caliper is innocent.

Check the cheap thing first. A hose is an hour; a modulator is not.