Brake Vacuum Pump Running Issue

[kaotik182]

A few years ago, I had the issue with the brake vacuum pressure sensor getting brake fluid on the sensor and my car going into limp mode. Pump was running the whole time driving. The dealer replaced the brake booster, vacuum pump, and sensor, which fixed the problem.

About 3 months ago, after I replaced the rear brakes with no brake fluid change, I noticed that after I start the car and press on the brake pedal repeatedly the vacuum pump runs for about 10 seconds and stops. I was just pumping the brakes before I move. When I pump/press the brake pedal 2 times after the pump stops and do not move my car, the pump runs again. It only stops doing this when I start driving. After I start driving, I can press the brake multiple times, and the vacuum pump does not run. The only time the vacuum pump issue comes back is when I turn off the engine and start it back up. I thought this was not normal. I checked for any codes, but there were none. I got the sensor replaced with a new one, but my car is doing the same thing after. Old sensor was dry and no brake fluid was around the area. Is this issue normal? I just do not remember this issue before, but I normally do not repeatedly press the brakes multiple times before moving. I only noticed this because of replacing the brake pads. I am leaning toward normal, but would like your input/testing your cars for this issue. Thanks!

[kaotik182]

Can a fellow M3 driver please try this on their car, so I can rule this out as normal? Just start the car and press/ pump the brake pedal a few times and the brake vacuum pump should start running. After the pump stops, pump the pedal a few times more and the pump should run again. This is all before you move the car. Drive around the block and try again before you turn off the car. You should hear no pump running. Thanks in advance.

[White 13]

I had the same problem as you described in the first post. Fixed the same way by the dealer and all has been well. I think mine comes on about the same as yours; probably not taking it out again until next weekend, so no help there.

I think I remember the tech saying the car does make some vacuum but not enough at times. I may have understood that wrong though. So the need for the pump at times.

Also found out not to fill the master cylinder to the full mark but leave it in the middle between max and min. When hot it expands and will vent. Factory and dealer like to fill it to the max.

[kaotik182]

Originally Posted by White 13

I had the same problem as you described in the first post. Fixed the same way by the dealer and all has been well. I think mine comes on about the same as yours; probably not taking it out again until next weekend, so no help there.

I think I remember the tech saying the car does make some vacuum but not enough at times. I may have understood that wrong though. So the need for the pump at times.

Also found out not to fill the master cylinder to the full mark but leave it in the middle between max and min. When hot it expands and will vent. Factory and dealer like to fill it to the max.

Thanks for the response!

I am going to chalk this one up as normal unless a code is thrown or anyone here has some better insight.

[White 13]

Kaotik
I have been listening to mine some this past weekend and it seems to come on every morning after sitting all night for about 5 to 10 seconds after the first use of the brake backing out of the garage. I haven't noticed it during the day after the first use.

I did try pumping the brake several times with the engine warm and it did not come on.

Re reading the first post: I didn't try it with the engine off.

I hope this helps some.

[kaotik182]

Originally Posted by White 13

Kaotik
I have been listening to mine some this past weekend and it seems to come on every morning after sitting all night for about 5 to 10 seconds after the first use of the brake backing out of the garage. I haven't noticed it during the day after the first use.

I did try pumping the brake several times with the engine warm and it did not come on.

Re reading the first post: I didn't try it with the engine off.

I hope this helps some.

White 13,
After the pump runs for about 5-10 seconds per your scenario you described, could you try pumping the brake several times right after it stops and let me know if the pump comes back on?

Just to clarify my first post, the scenarios I described should all be done with the engine on to test if the pump turns on. I have never heard the pump run with the engine off.

Thanks for your help!!!

[White 13]

I backed the car out today and oddly enough the pump didn't come on when I used the brakes like I said it did before. Maybe it had not sat as long as before or something.

I then pushed a few times and still nothing. Then I pushed it harder a few more times, maybe six times and the pump did come on.

So I guess the pump often comes on when using the brakes right after startup but not always. Further it seems I can get it to come on with enough pushing of the pedal while sitting idling. For the most part it doesn't seem to come on except maybe rarely when driving, but I maybe miss it when it does. I did hear while driving when the system was having trouble.

Seem like both of ours are acting similar. I didn't really drive it today to test it after a restart but like I said above, the first start after sitting for a day it didn't cause the pump to come on.

Seem like it is operating normal, what do you think?

[NashvegasR]

I have noticed same thing on my m3 -- in the first minute after startup, I hear that noise - guessing it's the pump running intermittently. It generally does it when I first start the M3, then I back down my driveway, when I get out to close my gate (with great efforts to not let the damn dogs escape!!), I almost always hear the noise again for a few seconds. Sounds like it's coming from bottom of left a-pillar area.

[kaotik182]

Originally Posted by White 13

I backed the car out today and oddly enough the pump didn't come on when I used the brakes like I said it did before. Maybe it had not sat as long as before or something.

I then pushed a few times and still nothing. Then I pushed it harder a few more times, maybe six times and the pump did come on.

So I guess the pump often comes on when using the brakes right after startup but not always. Further it seems I can get it to come on with enough pushing of the pedal while sitting idling. For the most part it doesn't seem to come on except maybe rarely when driving, but I maybe miss it when it does. I did hear while driving when the system was having trouble.

Seem like both of ours are acting similar. I didn't really drive it today to test it after a restart but like I said above, the first start after sitting for a day it didn't cause the pump to come on.

Seem like it is operating normal, what do you think?

From my experience, I think it's acting normal. I just don't like hearing that pump running. It just reminds me of that time when the vacuum system had that issue and then my car went into limp mode. I hope to not experience that again. Thanks again for your help!

[kaotik182]

Originally Posted by NashvegasR

I have noticed same thing on my m3 -- in the first minute after startup, I hear that noise - guessing it's the pump running intermittently. It generally does it when I first start the M3, then I back down my driveway, when I get out to close my gate (with great efforts to not let the damn dogs escape!!), I almost always hear the noise again for a few seconds. Sounds like it's coming from bottom of left a-pillar area.

You guessed right about the noise. It's the pump. Your scenario sounds like it's working normal too. It's when you hear it run more than that is when it's a problem. Just before my car went into limp mode, I heard it the whole time driving.