Car brakes hard during early in the mornig ?

[arwc]

Hi bros and sis, just wanna ask is it normal for the car brakes turn hard after parking for 5-6 hours ? It seems quite hard to start the car as we need to press on the brake pedal and start the car.Mine is a 2006 E90 325i, have changed all the brake pads last week to ATE pads and both of the sensors have been replaced too.Brake fluid have been changed as well (Bosch Dot 4) and did bleeding too.

 

[seewai]

My '09 E87 has hard-to-press brake pedal too but still manage to start the car so far. Maybe I've been stepping hard enough.

 

[skyblind]

Yea the brake pedal is damn hard during cold start.. Is that normal?

 

[aidilj]

Maybe somebody has been pressing the brake pedal when the engine is off - using all the vacuum in the brake booster. Lack of vacuum will cause a harder to press brake pedal. Either that or there's a leak in the brake boost component. Cheers.

 

[seewai]

Maybe somebody has been pressing the brake pedal when the engine is off - using all the vacuum in the brake booster. Lack of vacuum will cause a harder to press brake pedal. Either that or there's a leak in the brake boost component. Cheers.

Confirm no one pressed the brake pedal before start-engine.

And no need to wait til next morning to get a hard-brake-pedal, a few hours in a rainy afternoon would do enough to give it a hard-on.

 

[aidilj]

Confirm no one pressed the brake pedal before start-engine.

And no need to wait til next morning to get a hard-brake-pedal, a few hours in a rainy afternoon would do enough to give it a hard-on.

Just to confirm that the brake booster is causing the hard-on. If you step and hold on the brake and turn on the engine does the brake become soft or drop lower towards the floor?

 

[seewai]

Just to confirm that the brake booster is causing the hard-on. If you step and hold on the brake and turn on the engine does the brake become soft or drop lower towards the floor?

Yes it does become soft / lower towards the floor. For bro arwc's case, he couldn't even start his car so I don't think his brake pedal will go limp.

 

[gameover]

Maybe somebody has been pressing the brake pedal when the engine is off - using all the vacuum in the brake booster. Lack of vacuum will cause a harder to press brake pedal. Either that or there's a leak in the brake boost component. Cheers.

How do you troubleshoot/identify that it's a brake boost component leak? Mine is occasionally like that.

 

[aidilj]

This seems to be a common/widespread problem and there's a service bulletin on it. Read link below. At least, you push-to-start guys would be given a hint that the brake booster is leaking, we turn-the-keys group wouldn't have any idea that there's a slow vacuum leak.

Cheers

http://www.bimmerfest.com/forums/showthread.php?t=165292

 

[arwc]

tq for the replies bros hrmm mine is easy to start the car only have to press hard on the brakes, no one uses the car except me hmm strange, i have replaced the brake servo and the master cylinder unit last week because my brake pedal reaches to the end when pressed... have checked the brake linings and replaced all the pads too... will send the car to the workshop to check on it... hopefully not the dsc unit giving problems

 

[3er]

I get that occasionally. Not often and inconsistent. I've left the car for days and it was ok. So its pretty hard to say how or when it happens.

 

[arwc]

Did fix all the rubber pipes and valves and now brake is all ok for now
Thanks to Kenny and Jason from Msport @ Aman Suria very nice and honest ppl

 

[docrayboy]

I love my 320d brakes....nice smooth and firm feel when I press the pedal and works like a dream! The pedal feel is very important and few car manufacturers get it spot-on right.

 

[seewai]

Did fix all the rubber pipes and valves and now brake is all ok for now
Thanks to Kenny and Jason from Msport @ Aman Suria very nice and honest ppl

arwc, what's the damage like to replace all the hoses and valves?

Thinking of going back to Ingress to get it done. Hope this is covered under warranty replacement.

Cheers.
seewai

 

[arwc]

arwc, what's the damage like to replace all the hoses and valves?

Thinking of going back to Ingress to get it done. Hope this is covered under warranty replacement.

Cheers.
seewai

Hi Bro Seewai in Bavarian auto they quote me the price of the servo and pump about rm4k plus the brake servo is about 2.2k and the brake pump 1.9k hoses about rm100plus each

 

[astroboy]

Item 1 is the brake servo unit, also known as brake booster, or vacuum booster etc. It's function is to leverage on the vacuum pressure created by engine piston's descending movement to assist/amplify the brake pedal input so our brake pedal don't feel hard when depressed. When the engine is off, the vacuum contained in the booster is sufficient for another 1~2 braking application before losing the vacuum.

Item 12 is a non-return valve to keep the pressure contained. If this valve fail, hard pedal will be felt immediate after engine is shut.

Only 2 possible leakage of vacuum, one is the item 12 non return valve, cheap replacement and the other is the booster diaphragm.

Also sometimes when we stop our car and shut the engine.. we unconsciously/conveniently press the brake few more times after the engine is killed just to check and see if the handbrake is secured, that would release the vacuum pressure in the booster and the next time you want to step the brake and start the engine, you feel the pedal is hard (no more vacuum ma).. so this can also be one of the reason.

 

[aidilj]

Engine the engine is off, the vacuum contained in the booster is sufficient for another 1~2 braking application before losing the vacuum.

Also some time when we stop or car and shut the engine.. we unconsciously press the brake few more times after the engine is killed just to check and see if the handbrake is secured, that would release the vacuum pressure in the booster and the next time you want to step the brake and start the engine, you feel the pedal is hard (no more vacuum ma).. so this can also be one of the reason.

Spot on, the one or two times after the engine is off is designed for safety, so that the car can be stopped in case of emergency.

Some people also unconciously use the brake pedal as leverage when going out of the car.

 

[astroboy]

The N42 and N46 has added vacuum pump to the back of the engine as oppose to the conventional intake manifold vacuum for obvious reason, improve braking la.. M43 don't have this vacuum pump, hence less mechanical problem like seal leaks and what not.

N46 vacuum pump, Item 2:

This is the M43 brake booster vacuum hose connection [over the red dipstick], despite left hand drive, the manifold connection is the same.. it plug directly into the intake manifold. No vacuum pump era.. less headache?! :4:

This is how the N42/N46 vacuum pump works:
[video=youtube;rNXLSlkXqtQ]http://www.youtube.com/watch?v=rNXLSlkXqtQ[/video]

 

[arwc]

The N42 and N46 has added vacuum pump to the back of the engine as oppose to the conventional intake manifold vacuum for obvious reason, improve braking la.. M43 don't have this vacuum pump, hence less mechanical problem like seal leaks and what not.

N46 vacuum pump, Item 2:

This is the M43 brake booster vacuum hose connection [over the red dipstick], despite left hand drive, the manifold connection is the same.. it plug directly into the intake manifold. No vacuum pump era.. less headache?! :4:

This is how the N42/N46 vacuum pump works:
[video=youtube;rNXLSlkXqtQ]http://www.youtube.com/watch?v=rNXLSlkXqtQ[/video]

Thank You Astroboy very useful info

 

[aidilj]

Was just reading more about this, valvetronic engines need the vacuum pump because due to the valvetronic system, very little vacuum is created in the intake manifold for the brake servo.

there will be no vacuum because once the engine started, the throttle will open all the way and air intake controlled by valvetronic motor.