Absolutegtr

Hey guys. Im having an issue with my 2008 BMW 550i M-sport. The issue I am having is a hard brake pedal at idle and it is quite difficult to brake the car when coming down from speed and especially at say the last 5mph.

After HOURS of research I found that there was a recall for this problem. So I called the several dealers. The one closest to me said that the recall was already done, but then went on to say that he has never heard of such a recall The second dealer I called said no such recall has ever existed and my cars VIN does not have any OPEN recalls. So it seems I am all on my own.

Anyways, I am a very hands on person so I took on the challenge of trying to diagnose the problem my self. I noticed the vacuum pump leaking so i took it apart and replaced both o-rings as well as some RTV on the larger o-ring, When I took it apart I noticed the pump had oil in it, so I thought YES! I found the culprit. But im now thinking that the pump is SUPPOSED to have oil in it, correct? So anyways I assembled everything back together and I am still having the hard brake pedal at idle.

I checked the line and check valve running to the brake booster and found no oil anywhere in the line and verified that it was indeed drawing vacuum at the check valve (right before entering into the booster) No leaks found.

What else is the issue?

Thanks

turboawd

well if the line has vacuum by the booster, and brakes dont work, then i'd like to think the booster has gone bad. there is a diaphram inside that can rip or tear, particularly if oil got in there. which is one thing the recall was supposed to check, and replace the booster if necessary.

Absolutegtr

Is there a way I can tell if the booster has gone bad?




Also how much vacuum should the pump be pulling?

abe76247

The pump should make 24 inches or more.
Check the pump deadheaded (pull hose off booster and check so the booster is not able to bleed the vac away). Then attach hose to booster with vacuum pump T'd into system so you can see if the vaccum builds once it evacuates booster. If pump does good vac w/o booster and poor vac w/booster then it is booster.

Absolutegtr

Thanks will do as soon as I can locate a vacuum gauge.


The reason I am thinking bad/weak vacuum pump (even though they don't seem to go bad) is because I can get a nice, normal brake pedal at idle for like 1-2 pumps but then after that, the pedal becomes hard, and will actually sometimes push my foot back up while I'm trying to stand on the pedal!

Dishoom

I had the vacuum hose recall performed in 2010, and just found out today that my brake vacuum pump now needs to be replaced due to an oil leak. The oil leak could end up contaminating the brake fluid and damaging the master cylinder itself. I was quoted about $800 just to replace the vacuum pump.

turboawd

there is a recall that has to do with the check valve on the pump, allowing oil into the vacuum line going to the booster. if oil were to make it there, it may ruin the booster. not the master cylinder. there is a recall to take care of this issue.

if you have an external leak, the vacuum pump cover just needs to be resealed. very cheap to do. and wont effect your brakes. search for the how-to.

H F

Pull the vacume hose off the brake booster and check for oil inside the booster. if oil got in there it could be the problem

abe76247

An oil leaking vacuum pump is not a risk to the booster but that sure sounds like the way to sell it if you are a service advisor wanting that commission.

Those vac pumps are fed engine oil to keep the housing well lubed for the plastic vanes that run inside.
The cover is not rigid enough and does a poor job of keeping equal pressure on the cover seal.
The same pump on newer cars has a steel cover but they may leak when they get 5-7 years old, time will be the test.

Cricketts

Exactly what happened to my car and in the same time frame. Cost was $1,125.00.