Why is my parking brake light coming on while I'm driving?

Dear Car Talk

Dear Car Talk | Jun 01, 2000

Dear Tom and Ray:

I own a 1990 Toyota Corolla with a manual transmission. The parking-brake light on the dashboard has started to come on. This is fine when I have the parking brake on, but now it happens when I am driving, too. It seems to come on when I depress the regular brake pedal -- for instance, when I'm slowing down for a stop sign. Do you know what's causing this? -- Steven

TOM: Yes. You're low on brake fluid, Steven.

RAY: The "brake" light on the dashboard usually serves two purposes. One is to remind you that the parking brake is applied, so you don't drive to your mother-in-law's house in Dubuque with the rear brakes smoking.

TOM: But the light also comes on when your brake fluid is low. The fluid can be low because you have a leak. Or because your brake pads are worn out.

RAY: Most likely, the pads have worn out. When that happens, the space where the "padding" used to be gets filled by more brake fluid. That lowers the fluid in the reservoir and trips the "brake" light. Your pads might be right on the hairy edge now, which is why the light is only coming on intermittently. Eventually, though -- as the pads get worse -- the light will stay on all the time.

TOM: But there IS a chance that you have a brake-fluid leak. And if you lose enough of your brake fluid, you won't be able to stop at all. That would be bad, Steven. Ask anyone in an Alfred Hitchcock movie.

RAY: So if you're not dead by the time you read this, please take it in and get it checked out right away.

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