Brake booster going or vacuum pump?
 

Looking for ideas here please.

Brake assistance at idle is week on 2 or 3rd push of the pedal while at engine idle.

For example when parallel parking or driving in slow traffic you have to stomp really hard on the pedal after idling a few feet and then using brakes 2 or 3rd push.

Zero sponginess in the pedal, it's a rock, and when you step really hard the brakes work great.

Any engine speed above idle and the pedal feels normal.

Only other thing I can think to mention is hearing a faint sound from the engine bay while holding foot on brakes. Almost sounds like running water does in the house pipes from a few rooms away. Not a loud sound, may not be new, and I may be noticing it now since while troubleshooting.

I ordered Ordered vacuum pump seal kit from BMP Design to try but I'm not sure if this will fix.

http://www.bmpdesign.com/search_resu...h_query=305162


Thanks
Junkycosmos

2905 4.8is @ 92k miles

While waiting for pump seals I have found some interesting items

Anyone had this recall performed ?
http://www.bmwblog.com/2013/02/15/re...brake-failure/

I do see the line from vacuum pump to booster now has a 1way valve: (part6)
http://www.realoem.com/bmw/showparts...34&fg=27&hl=15

Google finds BMW V8s with loss of brake boost from vacuum pumps full of oil and oil backing up into booster pumps.

Anyone found their brake booster pump with oil in it?

Could be the pump,the vacuum line, the one way valve on the line, the booster, or any combination of those parts.

Here's what I would do after going through the same thing on a different BMW.

With the engine running check the pump by pulling the line entering the booster. It should have strong vacuum and be pulsing. If the vacuum is steady without pulsing it can mean the one way valve on the pump body outlet has failed. Replace pump.

While the vacuum line to booster is pulled, shine a light into the booster. Any oil in there will indicate oil passing through both the pump body check valve and line check valve. Replace pump, line check valve, and I would be replacing the booster too.

Check pump body for oil leaks. If the vacuum is strong and pulsing and there is no oil in the booster, you can re-seal the pump by replacing the pump body o-rings. There are 2, and I believe there are kits on-line for this.

Check the vacuum line/check valve assy by submerging one end in water and blowing through it. Any bubbles in the water and the valve is no longer sealing, an needs to be replaced.

No oil in booster, strong pulsing vacuum, and no leaks in vacuum line and check valve, I'd replace the booster.

Overdue for an update here. Will post back a case summary with full details later. Right now a quick post to tell you all I found my issue. I indeed have oil in my brake booster. Three calls to BMW North America and one to the dealer everybody swore up-and-down this car was not involved in the recall for oil and brake boosters, seems to be a different story and the braking system in the 4.8is matches many of the other cars that were involved in the recall.


http://img.tapatalk.com/d/14/07/25/be9amuqu.jpg

At these now I know the new booster should fix it.

A few weeks ago I did change the vacuum pipe between the vacuum pump and the booster. Of note my pipe was completely dry however the one-way valve and it was toast. New vac line from BMW actually contains two one-way valves one at the booster and one midway
http://img.tapatalk.com/d/14/07/25/za9ubere.jpg

Junkycosmos
2005 X5 4.8is

http://img.tapatalk.com/d/14/07/25/hu7y2e8u.jpg

Inside old booster

http://img.tapatalk.com/d/14/07/25/gyrazune.jpg
Old booster

http://img.tapatalk.com/d/14/07/25/5eme4aty.jpg

Above the brake pedal

http://img.tapatalk.com/d/14/07/25/ujy7a9a3.jpg

Fairly easy to slide the old booster out toward fender and new unit in without removing the heater cowl or plastic wall that holds the positive batt terminal.

Yup, same thing I went through. Good you got it all sorted out, I spent some time sorting all of it out on my own.