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E90/E91/E92/E93 (2006 - 2013)
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  #1  
Old 07-28-2013, 09:41 PM
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BMW4Lee BMW4Lee is offline
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Question Brake pedal issue when starting car

In October 2010, I started to have a problem where if I did not start the car for a day or so, the brake pedal was very hard. When the car starts, it's immediately OK again. However, the pedal will be OK when I start the car again (i.e., after an hour or so). I brought it to the dealer and they told me it was normal for the car has a harder pedal feel after a few days. I was told that when the pedal is harder, I just have to push the brake pedal a little more and the car will start fine. By starting the car, the vacuum pump engages, and the brake pedal is immediately normal.


Thanks to my research here, I found the following SIB:
SI B34 06 07
Brakes November 2007
Technical Service

SUBJECT
Additional Effort Required to Press Brake Pedal Prior to Engine Initial Start


MODEL
E90, E91, E92, E93 (3 Series) produced up to 9/07


SITUATION
A customer may report increased brake pedal effort prior to engine start. This situation can occur if the vehicle sits for extended periods of time. Although the brake pedal can be depressed, the customer may note a change in pedal feel.

CAUSE
The vacuum check valve, fitted at the brake booster, may leak due to component tolerances within the valve assembly.

CORRECTION
Replace the vacuum valve and hose assembly for the brake booster; refer to Repair Instruction RA 34 33 051.

PARTS INFORMATION
Part Number: 34 33 7 577 336
Description: Vacuum Pipe
Quantity: 1


WARRANTY INFORMATION
Covered under the terms of the BMW New Vehicle Limited Warranty.

Please refer to the latest KSD for all applicable labor operations and allowances.

If the appropriate labor operation is not contained in KSD, then a work time labor operation should be used.

Defect Code
34 33 00 14 00



Even though my car was produced in 10/2007, I got them to perform the SIB.

Since January 2011, I have not driven the car on a regular basis. It is kept on a battery charger when not in use. When I do start the car, I still experience this ďhardĒ pedal.

In November 2012, I left the car at the dealer for several days and they told me they could not duplicate the problem.

I brought it back again this week, and again, they could not duplicate the problem. When I went to pick it up, I walked with the SA to the car to start it in front of him. I got in the car and the pedal was hard. However, he said it was normal and it may have been "hard" because they were testing the brakes on the car the day before.

I just looked at my repair invoice from October 2010 and noticed that the part replaced was P/N 11 66 7 601 992 (which is different from what is stated in the SIB), so now I really donít know if the repair was done correctly or not.

I have never had a problem getting the car to start and the brakes work fine during driving. I donít bring the car in each time it happens because I am tired of dealing with them about this and the car is not my daily driver. However, it bothers me from time-to-time and that is when I decide to address the issue. At this point, I donít know if I should still continue to have them look at it or just live with it because I am not too fond of having them touching my car and not doing anything.

If anyone has insight into this issue, it would be appreciated. Thanks in advance for your assistance.
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  #2  
Old 07-29-2013, 03:00 AM
hondo402000 hondo402000 is offline
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I purchased a used 07-335i, had the same hard pedal issue after a few days. after reading posts I replace the check valve, which includes a section of the vacuum line, and it is also recommended that you replace the rubber grommet that goes into the brake booster body. its difficult but can be done, you have to take the ABS module loose and work around it, using hemostats and a screwdriver I was able to get the old grommet out and the new one in. After replacing those parts, the Hard brake problem seems to go away but I have noticed lately every once in a while I do have a hard peddle after about a week of setting. Unless it just bothers you to no end, and you are a DYIer, purchase the parts from BMW parts of south Atlanta and couple of hours you can replace it yourself, other than that it does not hurt the car in any way
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Old 07-29-2013, 11:57 AM
anE934fun anE934fun is offline
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Quote:
Originally Posted by BMW4Lee View Post
Snip...

If anyone has insight into this issue, it would be appreciated. Thanks in advance for your assistance.
One of the many 'issues' on my ex-E93 was the hard brake pedal. Both the check valve and the vacuum booster were replaced. There is some seepage once the engine stops, so don't be surprised at the hard pedal after the engine has been stopped for a day. With my ex-E93, the pedal would become hard 1/2 hour after the engine had stopped.

Still not satisfied, try another dealer.
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Old 07-29-2013, 12:09 PM
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DSXMachina DSXMachina is offline
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In the State of NH if a car has a hard brake pedal on start-up it fails inspection. You have a vacuum leak as mentioned in the SIB, and by other posters. It is NOT normal to have a hard pedal after a day or two. In fact, I have a '64 Lincoln in the shop which has a proper brake pedal after sitting for two weeks. If you lose vacuum boost within a couple days you certainly have a leak somewhere and it will get worse long before it gets better.
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Old 07-29-2013, 12:21 PM
anE934fun anE934fun is offline
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Originally Posted by DSXMachina View Post
In the State of NH if a car has a hard brake pedal on start-up it fails inspection. You have a vacuum leak as mentioned in the SIB, and by other posters. It is NOT normal to have a hard pedal after a day or two. In fact, I have a '64 Lincoln in the shop which has a proper brake pedal after sitting for two weeks. If you lose vacuum boost within a couple days you certainly have a leak somewhere and it will get worse long before it gets better.
I gave up trying to convince the SA about the not normal situation on the brake pedal being hard after the car sitting for more than a day (there was a bigger fish to fry what with the top water leaks). Even after switching dealers, the new dealer that ultimately stated the top water leaks were not repairable said that a hard brake pedal after the car sat for a day was 'normal'.

Fast forward to the present and my d can go for 2+ weeks of no starting and the brake pedal is not hard. Then, I drive the car for a week and it sits for a couple of days and the pedal is hard before I start the car. It is not something that can be reliably reproduced to show the SA, so I have just decided to live with the situation.

Should I be making an issue of this?
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Old 07-29-2013, 12:45 PM
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It was hard again this morning, so I brought it back in. Of course, they could not replicate the problem. They told me they are going to make a PUMA case to BMW and leave it in BMW's hands. My car is out of the regular warranty (although I do have the extended warranty), but my argument is that I brought it up to them prior to the expiration of the regular warranty.

When I went there today, I asked them why the part number on the invoice is different from the part number on the SIB. They looked it up and said the part number on the SIB superseded the part number on the invoice, but they are the same part. Now I wonder if the "old number" items were defective and that is why there is now a "new number" for the part.

I am not sure where the PUMA case will go, but I probably will just have to live with it. As I mentioned before, I am not fond of having them touching my car and not doing anything.
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Old 07-29-2013, 12:56 PM
anE934fun anE934fun is offline
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Quote:
Originally Posted by BMW4Lee View Post
It was hard again this morning, so I brought it back in. Of course, they could not replicate the problem. They told me they are going to make a PUMA case to BMW and leave it in BMW's hands. My car is out of the regular warranty (although I do have the extended warranty), but my argument is that I brought it up to them prior to the expiration of the regular warranty.

When I went there today, I asked them why the part number on the invoice is different from the part number on the SIB. They looked it up and said the part number on the SIB superseded the part number on the invoice, but they are the same part. Now I wonder if the "old number" items were defective and that is why there is now a "new number" for the part.

I am not sure where the PUMA case will go, but I probably will just have to live with it. As I mentioned before, I am not fond of having them touching my car and not doing anything.
If the initial retail delivery of your car occurred in California, and you reported the first incident of the hard brake pedal during the warranty period, you should be covered on the cost of the repair. BMW may attempt to push back on covering the repair, but just say no. If need be, an attorney will sort things out very quickly.

Edit: I just noticed you did a ED on your car. That may be a complicating issue. Then again, it may not if the car was first delivered in the U.S. in CA.
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Old 07-29-2013, 01:29 PM
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Is this something different than the Lemon Law? I had a car taken back under the Lemon Law close to 20 years ago. Back then, you had to bring it in 4 times for the same issue during the warranty period. If BMW doesn't figure out a way to resolve it, I will probably just live with it. Are you going to push the issue on your 335d? I bet a lot of BMW drivers -- especially the non-fanatics like us here -- have this problem and don't even realize it.
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Old 07-29-2013, 02:01 PM
anE934fun anE934fun is offline
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Quote:
Originally Posted by BMW4Lee View Post
Is this something different than the Lemon Law? I had a car taken back under the Lemon Law close to 20 years ago. Back then, you had to bring it in 4 times for the same issue during the warranty period. If BMW doesn't figure out a way to resolve it, I will probably just live with it. Are you going to push the issue on your 335d? I bet a lot of BMW drivers -- especially the non-fanatics like us here -- have this problem and don't even realize it.
Lemon law could be one remedy. The reason I asked where initial retail delivery occurred is to see if CA lemon law could be an option. If you reported the first instance of the hard brake pedal within the 18 months/18,000 mile period from initial retail delivery, you probably have a strong argument that CA lemon law has jurisdiction. If the hard brake pedal was first reported after the 18 months/18,000 mile period, there may still be a lemon law jurisdiction, it just gets more involved. Although a safety system (brakes) get treated differently.

Regarding the brake pedal on my d, it is too variable to be able to demonstrate the occurrence.
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Old 07-29-2013, 02:24 PM
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My first report was after 18 months, so I am out of luck there. The only problem with the brake pedal is at start-up -- it works fine during driving. Once I drive it to the dealer, when you push the pedal down to start the car, it is much softer. It is usually hard at start-up in the morning, and when I left there overnight, it was hard in the morning. The SA saw that, but now he says that is normal (he said it can range in hardness) as long as the pedal works fine during driving (which it does). I am not sure what the PUMA case will do as the dealer didn't even think a rep from BMW will come down to look at it. It is very frustrating.
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Old 07-29-2013, 02:35 PM
Pilgrim Pilgrim is offline
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Quote:
Originally Posted by BMW4Lee View Post
When I went there today, I asked them why the part number on the invoice is different from the part number on the SIB. They looked it up and said the part number on the SIB superseded the part number on the invoice, but they are the same part. Now I wonder if the "old number" items were defective and that is why there is now a "new number" for the part.
This is standard for all manufacturers. Car part numbers are superceded all the time. You can always call another dealer and ask them to check the part numbers if you feel paranoid about it. Their answer makes perfect sense to me.


Quote:
Originally Posted by BMW4Lee View Post
As I mentioned before, I am not fond of having them touching my car and not doing anything.
That doesn't make a lot of sense to me. When they need to have the car to test it or check it out, let them do it. Whether work needs to be done is a separate issue. Unfortunately, this is not a convenient thing, but they can't fix what they can't get their hands on.

I do agree with others - if this is a vacuum leak issue, eventually it will get worse. In the meantime, after the car sits, I'd start the car and pump the brakes once or twice before driving away.
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Last edited by Pilgrim; 07-29-2013 at 02:43 PM.
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Old 07-29-2013, 03:05 PM
hondo402000 hondo402000 is offline
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its a known fact that it is the vacuum check valve leaks, they could have replace it with another bad check valve, Manufactures are not in the habit of throwing away a ton of parts if not all the batch is bad, so they will use up all existing parts before substituting the new updated part, but I can tell you that its not normal, it should hold vacuum for at least 1 week maybe longer

maybe ask your sales associate that if the brakes fail because of lack of vacuum boost( if you loose vacuum you will have to really stand on the brakes to stop) after you have complained several time about the issue and you loose brake boost and you hit and kill someone because you had no brakes that you will make sure the dealer ship is named in the lawsuit
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Old 07-29-2013, 03:31 PM
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BMW4Lee BMW4Lee is offline
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You raise a very good point. I am going to see what comes of this PUMA case, and if it does not result in a repair, I will tell them exactly what you said.


Quote:
Originally Posted by hondo402000 View Post
its a known fact that it is the vacuum check valve leaks, they could have replace it with another bad check valve, Manufactures are not in the habit of throwing away a ton of parts if not all the batch is bad, so they will use up all existing parts before substituting the new updated part, but I can tell you that its not normal, it should hold vacuum for at least 1 week maybe longer

maybe ask your sales associate that if the brakes fail because of lack of vacuum boost( if you loose vacuum you will have to really stand on the brakes to stop) after you have complained several time about the issue and you loose brake boost and you hit and kill someone because you had no brakes that you will make sure the dealer ship is named in the lawsuit
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Old 07-29-2013, 04:24 PM
aleks001 aleks001 is offline
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I had this issue and gave up on it. I replaced it with a new part and it didn't really fix the issue. What helped the most was using a rubber gasket compound to seal everything. I'm pretty certain that there isn't a part that BMW has that will fix this properly. Even the new part didn't really seal that tightly. This is what i followed and it helped a lot. But it was very hard to apply the gasket material on RHD cars as the space is really restricted around the brake booster valve. Currently I'm at about 12 hours of car off, before the pedal goes hard. I've literally just decided to not fix it, as it's pretty much impossible. BMW really should really produce a part that works, this is just sad for a manufacturer this prestige.

DIY on the helpful fix:
http://www.e90post.com/forums/showthread.php?t=589753
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Old 07-29-2013, 06:20 PM
anE934fun anE934fun is offline
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You raise a very good point. I am going to see what comes of this PUMA case, and if it does not result in a repair, I will tell them exactly what you said.
Telling a SA anything isn't going to accomplish much. If you get in an accident, it is your word against the SA's word. If you want resolution, you are going to have to develop a paper trail that can be shown to attorneys and ultimately (if a lawsuit gets filed) a judge. There is a saying - if it isn't in writing, it didn't happen.

Your next step at this point is to contact a lemon law attorney. They are the most qualified to determine what would be the best course of action to pursue. Everything else that is posted here or on any other forum is just opinion or speculation. I have had personal experience with the CA lemon law, but my first issue occurred within the first 250 miles and less than 1 month of ownership and I took delivery of the car in California, so there are a number of differences between my circumstance and yours.
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Old 07-29-2013, 07:37 PM
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DSXMachina DSXMachina is offline
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Quote:
Originally Posted by anE934fun View Post
I gave up trying to convince the SA about the not normal situation on the brake pedal being hard after the car sitting for more than a day (there was a bigger fish to fry what with the top water leaks). Even after switching dealers, the new dealer that ultimately stated the top water leaks were not repairable said that a hard brake pedal after the car sat for a day was 'normal'.

Fast forward to the present and my d can go for 2+ weeks of no starting and the brake pedal is not hard. Then, I drive the car for a week and it sits for a couple of days and the pedal is hard before I start the car. It is not something that can be reliably reproduced to show the SA, so I have just decided to live with the situation.

Should I be making an issue of this?
First let me describe what vacuum boost is and why it's important. There may be some readers following the thread who aren't clear on what we're talking about.

Your brake pedal connects to a long rod which passes into a large lozenge shaped chamber. There it passes through a diaphragm maybe 8 to 10" in diameter. On one side of this diaphragm is outside air, on the other is a vacuum source which is 'throttled' by the movement of the rod. The same rod continues on and enters the master cylinder where the force of the driver's foot is applied to the brake fluid through a piston in a cylinder.

The driver can exert maybe 50 lbs of foot pressure fairly easily but this is nowhere near sufficient to halt a 3500 lb. car at speed. The master cylinder multiplies this force hydraulically many times over, but that still may be insufficient force.

The job of the brake booster is to further magnify the force exerted by the driver to a point where the car seems to easily be slowed. How's it do that?

Air pressure at sea level is 16 psi (yes, I rounded up). Assume the diameter of the diaphragm in the brake booster is 10", that means it has 78 square inches of surface. If all the air is removed from one side of the diaphragm -by vacuum- then there is 78 sq. in. X 16psi = 1,278 more pounds of force being exerted on the pedal! In your worst panic stop nightmare you can't apply that much pressure, and if you could your seat would break backwards long before you reached that point.

So the importance of vacuum is more readily apparent; it's 'fuel' for stopping. That vacuum is generated by the intake manifold as a gasoline engined car is driven. It is stored in a reservoir (yes, an empty container) and should always be available. When you start your engine and step on the brake you should feel your brake pedal drop an inch or more. If it doesn't you have a "hard pedal". You still have brakes but would have to press tremendously hard to stop the car because you don't have the assistance of the brake booster.

Loss of vacuum means air leaked into the system somewhere. Usually it gets in through a grommet or a failed check valve ( a one-way valve), or a loose or cracked hose. It is an early sign that one day you may not have brake boost when you need it, when Granny Smith is on her way to church on Sunday morning and blows through the stop sign that wasn't there yesterday.

Vacuum generation in diesels is more complicated than in most gasoline engines and presents more points for failure. However, the failures are commonly the same ones which occur in gas powered cars. Personally I'd be concerned about an occasional hard pedal. Somethin' ain't right.

Last edited by DSXMachina; 07-29-2013 at 08:01 PM.
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Old 07-29-2013, 07:58 PM
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BMW4Lee BMW4Lee is offline
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Thank you for the explanation.

Let me describe for you what happens when I go to start my car: I put my foot on the brake pedal and press down and then I push the start button.

Most of the time (except when I have driven it to the dealer), the pedal moves maybe 1/4 of an inch and then I press the start button. On the second start (i.e., after the 5 minute drive to the dealer), the pedal will drop an inch or more prior to pressing the start button. Once the car has been started (first start or second start), the brake pedal functions as it always did.

This problem only happens prior to pressing the start button and never occurred for the first two years of ownership. The SIB was performed -- albeit with a part number that was superseded with a new part number (the one in the SIB) -- and I still have the problem. Perhaps the fact that they used the part with the old part number and not the one with the new part number is the problem.


Quote:
Originally Posted by DSXMachina View Post
When you start your engine and step on the brake you should feel your brake pedal drop an inch or more. If it doesn't you have a "hard pedal". You still have brakes but would have to press tremendously hard to stop the car because you don't have the assistance of the brake booster.
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Old 07-30-2013, 03:12 AM
hondo402000 hondo402000 is offline
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Honestly and in my case its probably just a very small leak and only affects the brake peddle when starting the car, once the car is running I think you will not have a problem with a big enough vacuum leak as to affect braking.

its is just annoying especially when I replace the check valve and grommet and I still have the same issue randomly
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Old 07-30-2013, 01:45 PM
fdriller9 fdriller9 is offline
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I've had this issue in my car since 2008. I've had the car new since May 2006.

I haven't had any issues with the brakes. I don't really care it's hard on start up. It behaves completely normally as I'm driving.

You guys have nothing to worry about. It's really personal preference to have the check valve replaced/have the "issue" fixed.
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Old 07-30-2013, 06:12 PM
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Zooks527 Zooks527 is offline
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Originally Posted by DSXMachina View Post
Air pressure at sea level is 16 psi (yes, I rounded up).
I've never heard of a rounding up strategy that goes to the next highest integer value and then adds 1 on top of it.
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Old 07-30-2013, 06:26 PM
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Nordic_Kat Nordic_Kat is offline
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Originally Posted by Zooks527 View Post
I've never heard of a rounding up strategy that goes to the next highest integer value and then adds 1 on top of it.
Maybe DSX figures the math is easier with even numbers.
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  #22  
Old 07-31-2013, 05:01 AM
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Zooks527 Zooks527 is offline
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Originally Posted by Nordic_Kat View Post
Maybe DSX figures the math is easier with even numbers.
Well, on the bright side, at least he's not constrained to using base 9.
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Old 07-31-2013, 05:04 AM
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Zooks527 Zooks527 is offline
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Originally Posted by DSXMachina View Post
It is stored in a reservoir (yes, an empty container) and should always be available. When you start your engine and step on the brake you should feel your brake pedal drop an inch or more. If it doesn't you have a "hard pedal". You still have brakes but would have to press tremendously hard to stop the car because you don't have the assistance of the brake booster.
All math kidding aside, serious question here.

Are you saying the pedal should drop an inch as the engine starts (which has been the case from day 1 with my car) or are you saying it should drop an inch before you press the start button?
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2009 335i xDrive coupe, Jet Black, Black Leather, Grey Poplar, Steptronic, ZPP, ZSP, ZCW, iPod/USB, HD radio, Parking Assist. Rear Fogs, Hardwire V1, ProFit G3.
ED May 12, 2009, Munich dropoff May 16, Redelivery June 22, 2009




Prior 33 years of cars: 1967 BelAir wagon / 1968 LeMans Tempest / 1970 Mustang Mach 1 / 1972 El Dorado / 1978 Corvette (kept until first Bronco) / 1981 Subaru GL wagon AWD / 1983 s10 Blazer 4x4 (big mistake) / 1985 Bronco 4x4 / 1996 Bronco 4x4 / 2004 Passat 4motion
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Old 07-31-2013, 01:32 PM
anE934fun anE934fun is offline
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Quote:
Originally Posted by Zooks527 View Post
All math kidding aside, serious question here.

Are you saying the pedal should drop an inch as the engine starts (which has been the case from day 1 with my car) or are you saying it should drop an inch before you press the start button?
Probably both. If you have a vacuum system that is perfectly sealed, the residual vacuum in the reservoir will provide a boost (ability to drop the pedal) until the stored vacuum is used up. Worst case, the vacuum boost will be produced once the engine is started. If no vacuum boost once the engine is started, the vacuum power-assist has failed and the car has a defective safety system.
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Old 07-31-2013, 02:00 PM
hondo402000 hondo402000 is offline
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if you have a serious vacuum leak so the brakes have no power assist the engine will most likely run rough as a sandpaper
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