Intermittent BRAKE indicator light issue?!?

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Hey guys, about three weeks back I was driving along and had the 'BRAKE' light come on and then went off within less than a second. I was thinking that I might have imagined it at first being that I was a little tired of work that day and it's the same light that is on when the parking brake is engaged as well. Then about a week later I was speeding up quickly from a stop sign and it happened again, this time it was on for roughly two seconds and went right back off again. I checked the fluid level in the reservoir and it's halfway between full and minimum so it doesn't seem to be a fluid level issue and the level wasn't perceptively lower than it was about a month ago when I checked it last. I then disconnected the parking brake switch wires to see if it would come on again while driving and after awhile it did, this time it was after slowing down about a second after I released the brake pedal while entering a turn in an intersection. I reconnected the parking brake switch since I had eliminated that issue.

What would cause the light to come on intermittently other than fluid level or the parking brake. I don't have a low pedal. The pedal doesn't sink at all over time if I sit on it at a stop sign for a few minutes, which would indicate an master cylinder internal leak. Since the brake fluid level hasn't gone down it isn't leaking out from a caliper.

I'm not sure what could be going on to cause this light to come on, it's come on about six times now, never at idle. It's come on twice near red line while accelerating, once in a turn, another time just randomly while driving at a constant speed on a level road driving straight, once immediately after getting off of the brake and one other time that I don't remember what the conditions were.

Where are the sensors that turn this light on, are they all in the master cylinder itself? Again, the brakes seem to be performing normally, if I stomp on them they act like any standard non-ABS car and lock up the tires as it always has.

What could this be?
 
Does your vehicle have low brake pad sensors?

What happens if you add a little more brake fluid to the master cylinder reservoir?

Tim
 
The switch on the parking brake may need adjustment.
BTDT.
Brakes may need adjustment. Drum brakes are adjusted by backing up and applying brake firmly.
Rear discs are adjusted by using the parking brake; several times.
Do these every so often.
My 2¢
 
Sorry, I forgot to mention year/make/model. It's a 1995 Geo Prizm(Identical to the Toyota Corolla). No low brake pad sensors and the front brakes have quite a bit of meat left and the back shoes are still looking good. I usually give the car a good hard brake when backing up when I'm in a hurry out of the driveway for work so that gets done pretty often and I use my parking brake every time I park since I have a stick shift.

I will probably be bleeding the brakes with a fresh quart of brake fluid hopefully tomorrow and I'll have the reservoir full once I am finished.

Is there anything else that could cause the light to come on?
 
Not sure about your vehicle, but some makes such as Subaru this can indicate an alternator getting ready to crater. The ground for the brake and some other warning lights comes through the alternator field circuit.
 
Sometimes the brake fluid level sensor does not completely open or close the circuit. when fluid level is good, resistance ought to be infinite. If it isn't, buy a new level sensor and install.
 
Very common that Toyo's have the alternator light connected to the brake light. It depends on the year.

Rear brakes almost NEVER EVER adjust by backing up and press firmly.

Not all rear disk brakes adjust with the hand parking brake lever.Some are simply self biasing like front disk brakes.
 
I had this problem on my last two Toyota PU's seemed to be an early morning cold weather problem for the first mile. Never had an issue with the brakes so I just learned to live with it.
 
I am with the alternator suggestion..90% of the time that is what is wrong...other 10% it is yout master cyclinder..get the charging system checked
 
My grandparents have an 03 mercury villager (nissan quest) almost right at 36000 the brake light came on in the cluster. IT has over 60000 on it now and have not found anything it could be. I got tired of looking around and said screw it, no problems thus far, just an annoying light.
 
I'll check the level sensor with my ohm meter and see what it comes up with. If the alternator light and the brake light are connected in some way, I haven't yet seen the brake light come on when the alternator light has come on(it has only come on with extremely low engine speeds like when you let off the clutch too quick from a stop sign and it almost stalls and the alt. light flickers a few times) and it is never on when the car is off and the alt. light is showing. It seems to be a separate circuit for the light because the power on light test includes the brake light, check engine light and a few others, but the alt. light is separate.

It seems that I probably don't need to worry about it though.
 
It still could be the brake fluid [because of a sticky indicator sensor], or a contact in the parking brake that is mis- adjusted or loose.
 
does the car have rear anti-lock brakes? i am pretty sure i was seeing the brake light illuminate as an indicator when the rabs system wasnt able to see a signal from the rear wheels. it would come and go since the condition causing the fault was intermittent.
 
I think it's just the lower fluid level in the MC reservoir tripping the fluid level sensor float in the cap. Report back after you've flushed and filled the brake fluid.
 
mechtech2, I already disconnected the parking brake switch and while driving the car the same behavior occurred.

chas3, No the car doesn't have anti-lock brakes at all, it was an option but I don't even want it, ABS wasn't my friend when I had my 02 Grand Am so I'm glad it isn't there.

I'm hoping I can get the fluid flush done this weekend. It will be the first time using the Mityvac I got back in June and I hope the bleeders aren't seized. The sensor seems to be in the bottom of the reservior as the wiring going to the MC is at the bottom and since there is a screen in the top I can't see in there but I'd say it's down in there and since the level doesn't seem that low it must really swish around in there for it to be dry.
 
Okay, the long awaited update on this situation. The weather has been coldish and other things were going on so things were a bit delayed. I finished the fluid flush and the light hasn't come on for a few weeks now. I didn't get the firmness increase in the pedal that I expected but it was a noticeable improvement in firmness. Possibly just the rear drum auto-adjusters not doing their job, but getting the tires to squeal with the brake pedal is no problem so I think that things are in good shape now.

cool.gif


UOA coming next week if not this weekend...
 
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