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2K views 27 replies 8 participants last post by  arkim989 
#1 ·
Hello,

The problem is; Car brakes on its own, happened twice already..


Was going at normal speed in the city than the car started braking on its own, brake pads started to smell, braking pedal was getting harder and sensitive, good thing there was parking lot to pull over. Once I stopped, tried to push brake pedal couple of times, the pedal was getting harder and harder and eventually it was that hard that I couldn't push it down anymore. What I did is unplugged the power from the ABS on ABS, and also unplugged the + from the battery. Than after a while connected everything back and tried tried to move the car, couldnt move it, brake pedal got a little softer but still couldnt move it, brakes i guess were on. Tried everything couple of times couldnt move the car, than when i plugged everything back again, pushed the pedal like 10-15 times really hard while running the car, than put the car on drive and it drove but the brake pedal was really soft and sometimes was hard.

Happened again today, tried to do the same thing, drive for like a mile than it auto brakes again.. and I had to repeat the steps for 1 more mile....

Any ideas on why its happening?? maybe replace ABS or Ignition switch.. braking fluid is on max "BRAKE, ABS, TRACTION CONTROL" signs are sometimes on sometimes off. bmw 525i sport 2002.
 
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#2 ·
New calipers maybe?
 
#11 ·
Let me get this straight, this issue occurred and then you added fluid?

Brown fluid can cause problems over time, brake fluid absorbs moisture turning it brown and moisture in the brake system can cause corrosion. Also "dirty" fluid has a lower boiling point and can cause low or soft pedal.
Also make sure you are using the fluid approved for your car,mixing brake fluid types is not recommended.

And yes, you can drive without ABS, you will just have normal braking.
 
#12 ·
Let me get this straight, this issue occurred and then you added fluid?

Brown fluid can cause problems over time, brake fluid absorbs moisture turning it brown and moisture in the brake system can cause corrosion. Also "dirty" fluid has a lower boiling point and can cause low or soft pedal.
Also make sure you are using the fluid approved for your car,mixing brake fluid types is not recommended.

And yes, you can drive without ABS, you will just have normal braking.
yes, I added a little more dot 4 fluid into the brown fluid that the car already had, on the next day when it occurred first time. the fluid seemed to be dirty..
 
#21 ·
Please,
There are a lot of ideas here,
~ ~ ~
I believe that your master cylinder is sticky,
IF the piston inside the cylinder does not return 100% it will not allow fluid to return into the resivour and once you use the brakes or even just drive the fluid will expand a very small amount and without being able to get into the Master and into the resivour the brakes will get harder and harder till they are locked,
Something is wrong with the master not allowing fluid to go back after you brake,
 
#22 ·
You are dealing with life and death issues here.
Take it to a pro for proper diagnosis and repair.

As suggested, maybe the MC is locking up. Usually the MC fails the other way around: it leaks ---> poor braking effect. Here the opposite happens, too much braking when you don't want it.
 
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