Does my Accord really need a new master cylinder?

Dear Car Talk | Jul 01, 1992
Dear Tom and Ray:
Susan
RAY: Well, Susan, it could be the master cylinder. Modern cars have dual braking systems, with each one operating two of the four wheels. And it's possible that half the master cylinder (representing one of the two systems) has failed or is very weak. But it's easy for your mechanic to check and see if you're getting correct brake pressure to all four wheels. If so, he'll know that the master cylinder is fine. And frankly, I'll bet the master cylinder IS fine.
TOM: In which case, I'd ask him to check the calipers again. The caliper is supposed to squeeze the pads together, so that they grab the disk from both sides. But if a caliper's slide is seized, then the pads will only squeeze from one side. In that case, you won't get any significant braking until you actually bend the disk to the point where it makes contact with the outboard pads.
RAY: That takes more effort on your part and more pedal travel, and would explain why you need to press the pedal so far before the car starts to slow down.
TOM: And even though Jack LaLane would be proud of the workout you're getting with this brake pedal, you really ought to have it fixed. The braking ability of the car is certainly diminished, and if you don't fix the brakes, you may have to add body work to the list of repairs this car already needs.
Susan
RAY: Well, Susan, it could be the master cylinder. Modern cars have dual braking systems, with each one operating two of the four wheels. And it's possible that half the master cylinder (representing one of the two systems) has failed or is very weak. But it's easy for your mechanic to check and see if you're getting correct brake pressure to all four wheels. If so, he'll know that the master cylinder is fine. And frankly, I'll bet the master cylinder IS fine.
TOM: In which case, I'd ask him to check the calipers again. The caliper is supposed to squeeze the pads together, so that they grab the disk from both sides. But if a caliper's slide is seized, then the pads will only squeeze from one side. In that case, you won't get any significant braking until you actually bend the disk to the point where it makes contact with the outboard pads.
RAY: That takes more effort on your part and more pedal travel, and would explain why you need to press the pedal so far before the car starts to slow down.
TOM: And even though Jack LaLane would be proud of the workout you're getting with this brake pedal, you really ought to have it fixed. The braking ability of the car is certainly diminished, and if you don't fix the brakes, you may have to add body work to the list of repairs this car already needs.
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