Does my Accord really need a new master cylinder?

Dear Car Talk

Dear Car Talk | Jul 01, 1992

Dear Tom and Ray:

My problem is with the brakes on my 1987 Honda Accord LX. The car has 45,000 miles on it, and is used primarily for trips around town. Anyway, my brake pedal seems to travel too far toward the floor before it starts to brake. My husband thinks there is a problem. My mechanic has checked over the brake system four times, and thinks that I need a new master cylinder. Before he came to this conclusion, he checked out the whole system--the pads, rotors, cables, fluids, drums, etc. He said the car is safe, but agrees that the pedal travels too far before braking. He said he's not sure the car needs a master cylinder, but since he's checked everything else, he can't imagine what else it could be. What's your opinion?

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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