Time to stop and get that brake light checked
Dear Ask a Mechanic,
The last few really cold days my parking brake light has been coming on my dash. Sometimes it doesn’t happen until I use the roundabout to leave my neighbourhood, although once it was on when I started the car. It always goes away after a minute or two of driving, and the car seems to be working perfectly otherwise. I don’t use my parking brake, so why would the light come on? It’s a 2005 Toyota Corolla.
Seeing Red
There are a small number of vehicles that use separate lights for their parking brake and service brake warnings, but the vast majority — your Corolla included — use the one light for both functions. It’s unlikely the switch on your parking brake could be triggering the light without the handle itself being raised and the brake applied. Much more likely is that the light is coming on due to a problem with the service brakes — the main braking system that is applied by the pedal.
Your Corolla has a brake fluid level sensor. My guess is that the level in your master cylinder is low enough that it’s triggering the warning light. As fluids tend to expand and contract with temperature, when it’s very cold and the fluid has “shrunk” in the system, the light comes on. If it’s close to that switch point, it may only occur when the fluid sloshes to one side as you brake hard or go around a corner.
As heat from the brakes and engine warm up the fluid, it expands and the switch turns off the light.
Due to the potential seriousness of brake system faults, the cause for the low level needs to be determined right away. It could be as simple as worn brakes or as serious as a fluid leak, which can lead to brake failure.
It should be noted that automakers can also use a hydraulic pressure differential switch to activate the warning light in lieu (or in addition) to a fluid level sensor (it’s more common in older domestic models), and that the red light can also be activated by some ABS/stability system faults (usually accompanied by amber lights for those systems).
Driving with the brake warning on is inadvisable; any change in pedal feel or travel is immediate cause to have the vehicle towed to a repair facility.
ASK A MECHANIC IS WRITTEN BY BRIAN EARLY, A RED SEAL-CERTIFIED AUTOMOTIVE TECHNICIAN. YOU CAN SEND YOUR QUESTIONS TO WHEELS@THESTAR.CA. THESE ANSWERS ARE FOR INFORMATIONAL PURPOSES ONLY. PLEASE CONSULT A CERTIFIED MECHANIC BEFORE HAVING
Low brake level fluid levels are one reason your parking brake light may come on intermittently