Stiff Brake Pedal prior to start

horneth · 04-15-2019, 10:47 AM

Over the last 2 weeks, I've noticed that when i go to start the car, the brake pedal is very stiff. One time, the car would not start and I realized I had to press the brake very hard and I was able to start the car. Once started the pedal immediately softens to normal. Braking has been fine when driving, no issues at all.

Not sure if this is something I need to be concerned with. Any ideas what could cause this?

celsdogg · 04-15-2019, 05:20 PM

power brakes are usually vacuum assisted. there is a vacuum line going from the intake to the brake booster which helps us push the brake. when the car sits, air might get in and reduce the vacuum, then the pedal will be hard (i.e., no assist).

horneth · 04-15-2019, 06:58 PM

Quote:

Originally Posted by celsdogg

power brakes are usually vacuum assisted. there is a vacuum line going from the intake to the brake booster which helps us push the brake. when the car sits, air might get in and reduce the vacuum, then the pedal will be hard (i.e., no assist).

Thanks, this is helpful to understand what may be going on. I've owned the car for just over a year and the past 2 weeks is the only time I've experienced this. Sounds like it could be normal, just seems odd that I'm only recently experiencing it

ah100m · 04-16-2019, 12:40 PM

No, it's not normal. The vacuum assist system should hold vacuum indefinitely. You have a leak somewhere. It's most likely not serious just pay attention to the level of assist when you're driving. In stop-and-go driving if the pedal gets harder then you need to have it fixed.

horneth · 04-17-2019, 08:56 AM

Quote:

Originally Posted by ah100m

No, it's not normal. The vacuum assist system should hold vacuum indefinitely. You have a leak somewhere. It's most likely not serious just pay attention to the level of assist when you're driving. In stop-and-go driving if the pedal gets harder then you need to have it fixed.

Thank you! I'll have it checked out then.

kerny7678 · 04-17-2019, 09:36 AM

Quote:

Originally Posted by horneth

Thank you! I'll have it checked out then.

Get it checked. Had an issue like this in my previous car, a Saab, got to the point where I had to stand on the pedal with two feet to get the thing to stop. Scary

kern417 · 04-17-2019, 02:05 PM

That doesn't sound like OP's issue. He said braking is fine while driving, it's just hard while the car is off. That is normal. You can try it yourself, just pump the brake pedal after you turn the car off. I experience it sometimes depending on how my routine of getting out of the car goes, i.e. if i hit the brake multiple times for whatever reason.

It's just like when you bleed your brakes, you pump the pedal and it gets stiffer until you release the pressure.

Pure Driven · 01-12-2020, 02:22 PM

Quote:

Originally Posted by horneth

Over the last 2 weeks, I've noticed that when i go to start the car, the brake pedal is very stiff. One time, the car would not start and I realized I had to press the brake very hard and I was able to start the car. Once started the pedal immediately softens to normal. Braking has been fine when driving, no issues at all.

Not sure if this is something I need to be concerned with. Any ideas what could cause this?

Just wondering if you got this checked out. I started experiencing this myself recently and have never noticed it before since I've owned it a little less than a year now.

izaazk · 01-12-2020, 07:10 PM

I have the same exact issues as well as a hiss near the booster during cold climates and car has sluggish acceleration

kilogram · 01-14-2020, 01:44 PM

FWIW, power brake systems usually have a check valve in line to the booster that retains vacuum in the booster after the engine (or in our case, pump) is shut off. I'm guessing you have a bad check valve.

cfm56d7b · 01-19-2020, 12:02 PM

horneth, is your car under warranty by any chance? If yes - a visit to the dealer would be very prudent.

The symptoms you are describing are not normal. Please get your brakes inspected.

uluwatu06 · 03-17-2021, 01:34 AM

My wife and i experienced this a few times over the past 5 mths on her 330i. It was still under warranty so we sent it in.

The next day, we were informed that the battery was replaced and the car is ready to be collected. Since we collected the car in Sept 2020, the Start/Stop function rarely kicks in... so all along i suspected the battery level was already quite low and on the way out. But i did not link the stiff brake pedal to the battery after having read quite a bit in this forum.

After we collected the car from the AD, we were told to monitor this closely.

We left the car untouched for like 5 days recently but the brake pedal did not stiffen at all. I hope it stays this way.

In summary, i am not sure if this stiffening of brake pedal has anything to do with the low battery.

04-15-2019, 10:47 AM	#1
horneth New Member 3 Rep 9 Posts Drives: 2014 BMW 320i Join Date: Feb 2018 Location: Central Florida iTrader: (0)	Stiff Brake Pedal prior to start Over the last 2 weeks, I've noticed that when i go to start the car, the brake pedal is very stiff. One time, the car would not start and I realized I had to press the brake very hard and I was able to start the car. Once started the pedal immediately softens to normal. Braking has been fine when driving, no issues at all. Not sure if this is something I need to be concerned with. Any ideas what could cause this? __________________ 2014 320i Sport Package - Lighting Package - M3 Style Front Bumper & Mirror Caps, M-Performance Rear Bumper & Side Skirts, 335i Dual Exhaust
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04-15-2019, 05:20 PM	#2
celsdogg E4 Mafia 323 Rep 412 Posts Drives: E30, E36/5, E46, F22, F30 Join Date: Apr 2018 Location: MD iTrader: (0) Garage List 1990 BMW 325i [0.00] 1998 BMW 318ti [0.00] 2003 BMW 325i [0.00] 2015 BMW 335i [0.00] 2015 BMW M235i [0.00]	power brakes are usually vacuum assisted. there is a vacuum line going from the intake to the brake booster which helps us push the brake. when the car sits, air might get in and reduce the vacuum, then the pedal will be hard (i.e., no assist). __________________ Squad - '90 E30 325i MT (225k) \| '98 E36/5 318ti MT (153k) \| '03 E46 325i MT (152k)\| '15 F22 M235i MT (60k) \| '15 F30 335i MT (80k) KIA - '91 E30 325i AT (146k) \| '02 E46 325i MT (212k) Bring back the purple M stripe
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04-16-2019, 12:40 PM	#4
ah100m Enlisted Member 0 Rep 33 Posts Drives: E90 328xi, 56 Healey 100m Join Date: Oct 2006 Location: Long Island NY iTrader: (0)	No, it's not normal. The vacuum assist system should hold vacuum indefinitely. You have a leak somewhere. It's most likely not serious just pay attention to the level of assist when you're driving. In stop-and-go driving if the pedal gets harder then you need to have it fixed.
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01-12-2020, 07:10 PM	#9
izaazk Captain 140 Rep 625 Posts Drives: 2013 335i Join Date: Aug 2016 Location: Chicago, Illinois iTrader: (1)	I have the same exact issues as well as a hiss near the booster during cold climates and car has sluggish acceleration
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01-14-2020, 01:44 PM	#10
kilogram Private 70 Rep 79 Posts Drives: 340i xDrive Join Date: Jan 2020 Location: Commerce City, CO iTrader: (0)	FWIW, power brake systems usually have a check valve in line to the booster that retains vacuum in the booster after the engine (or in our case, pump) is shut off. I'm guessing you have a bad check valve.
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01-19-2020, 12:02 PM	#11
cfm56d7b Lieutenant General 5886 Rep 10,256 Posts Drives: 2017 440i Gran Coupe & 2015 X5 Join Date: Nov 2012 Location: Orange County, CA iTrader: (2)	horneth, is your car under warranty by any chance? If yes - a visit to the dealer would be very prudent. The symptoms you are describing are not normal. Please get your brakes inspected.
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03-17-2021, 01:34 AM	#12
uluwatu06 Private 22 Rep 86 Posts Drives: 2021 F44 BMW M235i xDrive Join Date: Sep 2015 Location: Middle East iTrader: (0)	My wife and i experienced this a few times over the past 5 mths on her 330i. It was still under warranty so we sent it in. The next day, we were informed that the battery was replaced and the car is ready to be collected. Since we collected the car in Sept 2020, the Start/Stop function rarely kicks in... so all along i suspected the battery level was already quite low and on the way out. But i did not link the stiff brake pedal to the battery after having read quite a bit in this forum. After we collected the car from the AD, we were told to monitor this closely. We left the car untouched for like 5 days recently but the brake pedal did not stiffen at all. I hope it stays this way. In summary, i am not sure if this stiffening of brake pedal has anything to do with the low battery.
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