00 Mustang Gt - Brake Light On Dash Comes On While Driving?

Discussion in 'SN95 4.6L Mustang Tech' started by jayrw, Dec 5, 2013.


  1. jayrw

    jayrw Member

    Joined:
    Sep 2, 2007
    Messages:
    149
    Likes Received:
    0
    Trophy Points:
    17
    Location:
    Clovis, California.
    For the last couple weeks the brake light on dash will come on usually when I apply the brakes, even just a light press and other times it will come on while driving without pressing brakes, symptom seems to reduce after car warms up but doesn't completely go away.

    Brake pedal pressure feels fine and brake fluid level is good.

    Any ideas appreciated.
  2. davis3

    davis3 Active Member

    Joined:
    May 7, 2006
    Messages:
    1,270
    Likes Received:
    40
    Trophy Points:
    49
    Location:
    CA
    Check the parking brake switch.
    Its under the center armrest, attached to the parking brake assembly.
    Could be going bad.


    Sponsored Ad

  3. wmburns

    wmburns SN Certified Technician

    Joined:
    Aug 14, 2009
    Messages:
    3,057
    Likes Received:
    52
    Trophy Points:
    69
    Location:
    Houston Texas
    Does the light come on during HEAVY braking? If so, it's from the fluid shifting in the master cylinder and it's normal. Best to confirm that the master cylinder is full.
  4. davis3

    davis3 Active Member

    Joined:
    May 7, 2006
    Messages:
    1,270
    Likes Received:
    40
    Trophy Points:
    49
    Location:
    CA
    That was my first thought too, but in his post he states the fluid level is good.
  5. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt" SN Certified Technician Founding Member

    Joined:
    Feb 19, 2001
    Messages:
    21,365
    Likes Received:
    252
    Trophy Points:
    124
    Location:
    Massachusetts
    Id just add a bit more fluid. The BRAKE light only has two inputs, the emergency brake has a switch on it that turns the light on when you pull the E-brake, or the low fluid sensor in the master cylinder.

    Since you state it comes on when braking, it's most likely fluid shifting around in the MC. Try adding a tad bit more fluid and see if that solves the problem
  6. VOORHEES

    VOORHEES Stangnet's "35th Limited Edition" VIN Guy Mod Dude

    Joined:
    Nov 9, 1999
    Messages:
    3,181
    Likes Received:
    16
    Trophy Points:
    69
    Location:
    LaGrange, GA
    I had this issue until I had caliper failure on the drivers side. One piston was not moving in and out as it should. I had both of them replaced on the front.
  7. jayrw

    jayrw Member

    Joined:
    Sep 2, 2007
    Messages:
    149
    Likes Received:
    0
    Trophy Points:
    17
    Location:
    Clovis, California.
    Thanks for the feedback I'll try adding a little fluid tomorrow and go from there, wouldn't be surprised if one of the pistons is acting up either i've been wanting to replace the front calipers.
  8. sneaky98gt

    sneaky98gt Mustang Master

    Joined:
    Apr 24, 2008
    Messages:
    3,184
    Likes Received:
    150
    Trophy Points:
    94
    Location:
    NC State University
    As mentioned earlier, there's only 2 things that can cause that light to come on. The sensor in the reservoir (which, if functioning properly, only comes on if the fluid is low), or the E-brake handle. The brake calipers have nothing to do with the light.

    Also, you will know if your brake calipers are sticking. There will be a noticeable resistance while driving, the entire brake/wheel assembly will get very hot, and the brake pads will wear very quickly.
  9. wmburns

    wmburns SN Certified Technician

    Joined:
    Aug 14, 2009
    Messages:
    3,057
    Likes Received:
    52
    Trophy Points:
    69
    Location:
    Houston Texas
    +1 on how the brake warning system of the Mustang works. Only two methods will activate the dash warning light.

    However, the brake system on my 2000 GT is in perfect running order. The fluid level is at/near the "max" level. My brake warning light will come on during very HEAVY high speed braking. My thought process had always been that the heavy braking is shifting so much fluid to the front of the res, that the sensor sinks thus making the dash warning light come on.

    My brake warning light goes out when braking is reduced.

    Since in my case, the light only comes on during unusually heavy braking or when the E-brake is actually set, I have considered it normal operation.

    To the OP, if the brake light comes on frequently, this may indicate a problem.

    If on the other hand the warning light only comes on when you are going very fast and really braking hard, and you are certain the level is correct, IMO it may not indicate a problem.
  10. sneaky98gt

    sneaky98gt Mustang Master

    Joined:
    Apr 24, 2008
    Messages:
    3,184
    Likes Received:
    150
    Trophy Points:
    94
    Location:
    NC State University
    My car is the exact same. It doesn't do it under normal driving conditions. But on an emergency stop (i.e. I'm doing everything I can to get the car stopped as soon as possible), it'll come on for a couple seconds. And that's with the fluid a little over the full line. If it gets low at all, it'll sometimes even come on during hard acceleration.
  11. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt" SN Certified Technician Founding Member

    Joined:
    Feb 19, 2001
    Messages:
    21,365
    Likes Received:
    252
    Trophy Points:
    124
    Location:
    Massachusetts
    Unplug the low fluid sensor. Drive around for a few days. If the light is gone, and never appears again, it's the low fluid sensor issue.

    Either the fluid is violently sloshing around and momentarily closing the switch on the sensor, or the sensor is failing.
  12. jayrw

    jayrw Member

    Joined:
    Sep 2, 2007
    Messages:
    149
    Likes Received:
    0
    Trophy Points:
    17
    Location:
    Clovis, California.
    Well looks like I just needed to add a very small amount of fluid in the reservoir, the light hasn't come on since then.

    Thanks again.
  13. trombonedemon

    trombonedemon Well-Known Member

    Joined:
    Jun 25, 2009
    Messages:
    2,518
    Likes Received:
    28
    Trophy Points:
    59
    Location:
    U.S.A, U.S.A., U.S.A.!

Share This Page