gwf545

I would not hesitate to do it myself, however, you probably will need to disconnect brake lines in order to remove the master cylinder. This means you will need to bleed the brake system and might want to consider purchasing a pressure bleeder. I've changed out my brake fluid using one and it is a lot easier than having someone pump the pedal while you open and close the bleeders. Search the DIY forum for details on doing this. I am pretty sure I saw something posted there. It would be a lot better if the Service Manual from Bentley were available, but that is still a few weeks away.

turboawd

first thing i would do is check the hose that goes from the brake booster to the vacuum pump (#5 in pic)
there have been known cases of the vacuum lines cracking.

the vacuum pump is located on the front side of the passenger cylinder head. the vacuum line runs from there, across the front of the engine, and then rearward torwards the brake booster.

545iBMW

Checked the parts you mentioned here and found the connection between the vacuum pump and the hose is loose (I can move it side to side about 1-2mm). Is this normal?

Thanks for all your inputs.

spandex

The connection shouldn't be loose (it wasn't loose on my 645 and isn't on my 545 either). This could be a cheap fix if it is the problem. I've heard of these symptoms being down to a faulty vacuum hose before, so it's worth doing that first before tackling the booster or pump.

kxmills

I had the same problem, it was my master cylinder. The diaphragm ruptured. I got mine from the dealer for $288. That is itme #1 in that diagram. The vacuum pump that someone is referring to is engine driven that's a little under $400. I believe these parts are available from Newport BMW.

higher

What you describe is a classic symptom of a failing brake-servo unit.

Just like any part in your car it can fail, I don't think this is necessarilly a fault with BMW because it can and does happen to all car brands.

545iBMW

We have owned 9 cars in the past 10 years.
My dad used to own a car lot when I was growing up and I would drive the cars and never had this issue before.
Cars are recalled for safety purposes (i.e. airbag, brakes, floor mat that causes unintentional acceleration, spare tire dropping due to corrosion, etc).
I think this more than justifies a recall because it is a known issue and its a safety issue.

turboawd

i believe you meant brake booster. but i dont think its the original poster's problem as his problem is intermittent. a ruptured booster would never work.

turboawd

is the hose loose or is the nipple on the pump loose? if its just the hose, then maybe you just need to recrimp the clamp. the nipple shouldnt be loose, and i believe there is a one way check-valve in there to hold vaccum in the booster.

i attached a pic of where the brake vacuum hose attaches.

545iBMW

Yes, that looks just about right.
I was able to call a shop today with good reviews (all 17 positive reviews from bimmershops.com) so I said, why not - so I called this morning. I spoke to the owner who answered the phone. Told him that I don't have the dough to pay for what the dealer was asking. He told me, he's going to diagnose it for free! Same as what the reviewers mentioned on the site. I will try and recrimp the clamp tomorrow morning before heading there and see if it fixes this issue. By the way, he seems very knowledgeable - he said that this is very common with 745i's, 645i's and 545i's.

I hope someone will benefit from this in the future as I know how frustrating to deal with a safety issue.