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Old 09-07-2019, 08:28 PM
primem primem is offline
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Location: Alberta, Canada
 
Join Date: May 2019
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Mein Auto: 2005 x5 4.4L
diagnosing a hard brake pedal

This might help someone with the same problem. 2006 x5 n53 4.4L

My symptom was a hard brake pedal. I would get one normal push and then a hard pedal until 5 seconds after the pedal is released. When the engine was shut off the brake pedal pushes up.

After a search I found a common issue was the mechanical vacuum pump leaking oil into the brake booster.
I removed the booster vacuum hose and it was oil free. video scope inside the booster was also oil free.
-connecting a vacuum gauge; at both pump test port and at the booster hose showed 26" of vacuum....plenty of vacuum.

I wanted to connect a vacuum gauge to the booster and see if the booster could hold a vacuum but did not have an adapter to connect the gauge to the booster.

I did have a smoke machine and pumping smoke into the booster vacuum hose port showed the booster leaking smoke.
This must be a common problem as boosters from every parts store in town and rock auto were backed ordered.
anyone have a good source for boosters...not dealer...I won't pay $1000 for a booster.

Last edited by primem; 09-07-2019 at 08:29 PM.
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  #2  
Old 09-08-2019, 09:08 AM
Fifty150hs Fifty150hs is offline
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Location: Menlo Park, CA
 
Join Date: Jan 2016
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Mein Auto: SF Bay Area
Quote:
Originally Posted by primem View Post
This might help someone with the same problem. 2006 x5 n53 4.4L

My symptom was a hard brake pedal. I would get one normal push and then a hard pedal until 5 seconds after the pedal is released. When the engine was shut off the brake pedal pushes up.

After a search I found a common issue was the mechanical vacuum pump leaking oil into the brake booster.
I removed the booster vacuum hose and it was oil free. video scope inside the booster was also oil free.
-connecting a vacuum gauge; at both pump test port and at the booster hose showed 26" of vacuum....plenty of vacuum.

I wanted to connect a vacuum gauge to the booster and see if the booster could hold a vacuum but did not have an adapter to connect the gauge to the booster.

I did have a smoke machine and pumping smoke into the booster vacuum hose port showed the booster leaking smoke.
This must be a common problem as boosters from every parts store in town and rock auto were backed ordered.
anyone have a good source for boosters...not dealer...I won't pay $1000 for a booster.
FCPEuro. https://www.fcpeuro.com/products/bmw...rg-11667545384

By the way they have genuine BMW for $500.
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  #3  
Old 09-08-2019, 11:11 AM
primem primem is offline
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Location: Alberta, Canada
 
Join Date: May 2019
Posts: 35
Mein Auto: 2005 x5 4.4L
thanks...I will check them out.
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