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XBimmers | BMW X3 Forum > BMW X3 Forums | F25 (2011 - 2016) > Second Generation BMW X3 General Forum » Brake issue in hot weather

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      07-15-2015, 12:48 PM   #1
Tangsta
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Brake issue in hot weather

During a heat spell in the last week of June (the temperature was above 30*C / 86*F) my brake pedal started to sink under constant pressure and need to be depressed further and further to maintain the same braking force.

A few times at a stop, I'd be holding the brake pedal constantly and the car would start rolling forward again until I pressed the brakes further, all the way until it was about 1 inch off the floor.

I haven't read about any issues like this concerning F25s, but all other forums seem to point to a faulty master cylinder.

I took the car in to the shop a couple days ago, but with it being a relatively cool day, they weren't able to replicate the issue and the diagnostics ended there (after also checking for fault codes).

There's a lot of you in much warmer climates than here in Calgary... Anyone else experienced this issue? I feel like the dealership could/should have been more proactive, but I'm a bit at a loss as to what else they could do. Thoughts?
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      07-15-2015, 01:19 PM   #2
Radioactive
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No problems here in inland So. California.

Last time you had a brake bleed....brake fluid is hydrophilic.

Somewhere off the internet...."Because brake fluid is well known as a hygroscopic fluid, its molecular O-H structure easily allows hydrogen bonding with hydromolecules, e.g., H2O. The moist brake fluid reduces the boiling point and moreover causes the deterioration of the functionality of the brake system."
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      07-15-2015, 01:28 PM   #3
ChicagoNorthShore
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Quote:
Originally Posted by Tangsta View Post
During a heat spell in the last week of June (the temperature was above 30*C / 86*F) my brake pedal started to sink under constant pressure and need to be depressed further and further to maintain the same braking force.

A few times at a stop, I'd be holding the brake pedal constantly and the car would start rolling forward again until I pressed the brakes further, all the way until it was about 1 inch off the floor.

I haven't read about any issues like this concerning F25s, but all other forums seem to point to a faulty master cylinder.

I took the car in to the shop a couple days ago, but with it being a relatively cool day, they weren't able to replicate the issue and the diagnostics ended there (after also checking for fault codes).

There's a lot of you in much warmer climates than here in Calgary... Anyone else experienced this issue? I feel like the dealership could/should have been more proactive, but I'm a bit at a loss as to what else they could do. Thoughts?
It was just 90 degrees here in Chicago and I drove the car around all day and had absolutely no problems, must be your car.
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