Brake warning light on when braking.
04-05-2018, 01:19 PM
#1
Brake warning light on when braking.
In the morning when I head off to work or class, until the engine warms up, the break light on the dash lights up anytime I press the break. As the engine warms up it will take harder braking for the light to come on. Once everything has warmed up to normal temps the only time the light will come on is if I make an emergency stop. Should I be worried about this? The brakes have never failed and seem fine but the little red light is a little concerning. (This is also the same light that illuminates when you set the parking break.)
04-05-2018, 02:22 PM
#2
3rd Gear Member
Join Date: Aug 2015
Location: SE Michigan
Posts: 939
Yes, you should be worried about it. At least, until you find out what's causing it.
Low fluid can trigger that light. So can excessive brake wear, as more fluid is needed to fill the caliper piston bores. If fluid level is low, you'll need to inspect further and find out where it's going.
Low fluid can trigger that light. So can excessive brake wear, as more fluid is needed to fill the caliper piston bores. If fluid level is low, you'll need to inspect further and find out where it's going.
04-08-2018, 08:51 PM
#7
Level was a little low but still getting the light when cold. (Below 55*F or hard braking before engine gets to normal operating temperature) Also where can I find the master cylinder? I’m not very fimilar with much under the hood that isn’t electrical.
04-08-2018, 10:18 PM
#8
3rd Gear Member
Join Date: Aug 2015
Location: SE Michigan
Posts: 939
The brake fluid reservoir is mounted directly on top of the master cylinder. Every time you press the brake pedal, the master cylinder takes fluid from the reservoir and pushes it towards the brake calipers. I don't know how low "a little low" is, but if it gets down below the reservoir-mounted level sensor, it can trigger that warning lamp.
That same lamp can also be activated by a switch mounted on the parking brake mechanism. But since it's lighting up when you press the brake pedal, I'm inclined to think that it must be related to the regular service brake instead.
I'm also inclined to think that the temperature effect that you're experiencing might not be from the engine so much as it's coming from the brakes themselves. Each time you step on the brakes while driving, they generate friction and heat, which might be expanding the materials enough to allow even more fluid to return to the reservoir and better cover up that sensor. This would explain your having to push the pedal harder in order to trip the warning lamp as the car warms up.
That same lamp can also be activated by a switch mounted on the parking brake mechanism. But since it's lighting up when you press the brake pedal, I'm inclined to think that it must be related to the regular service brake instead.
I'm also inclined to think that the temperature effect that you're experiencing might not be from the engine so much as it's coming from the brakes themselves. Each time you step on the brakes while driving, they generate friction and heat, which might be expanding the materials enough to allow even more fluid to return to the reservoir and better cover up that sensor. This would explain your having to push the pedal harder in order to trip the warning lamp as the car warms up.
04-08-2018, 10:22 PM
#9
That all makes sense to me. And by a little low I mean it was about a quarter of an inch below the low mark on the reservoir. When I check the master cylinder what exactly will I be looking for? Will I be checking if it’s loose or if it is leaking?
04-08-2018, 10:50 PM
#10
3rd Gear Member
Join Date: Aug 2015
Location: SE Michigan
Posts: 939
There's not much to visually inspect on the master cylinder itself. If you do happen to spot a leak, then by all means, pursue that. But an internal failure won't be as obvious, and it won't drain the reservoir either (except in the unlikely event that it started puking fluid into the booster).
But if the level is below the LOW mark, then it must indeed be tripping that sensor. This is not an electrical problem. Fluid is either leaking somewhere, or you have extreme brake wear.
But if the level is below the LOW mark, then it must indeed be tripping that sensor. This is not an electrical problem. Fluid is either leaking somewhere, or you have extreme brake wear.
