bmwe21.net forums

My 1983 320iS has been sitting for over 6 months. I went to drive it today and had no brakes. It appears that there isn't any vacuum boost(?). The brake fluid is full and there doesn't appear to be any leaks. I've tried pumping the brakes, however, the pedal just goes to the floor. I had to use the emergency brake to stop.

Where should I begin testing? I don't want to just start purchasing random parts to replace.

As always, any help is greatly appreciated! Thank you!!

Could be several things, but if you are sure the level in the reservoir is ok, than it could be there is no vaccuum on the booster. I would start there. It is not very likely that it fails at all 4 individual brakes, so it is more likely that is is somewere in the booster, pedal of master brake cilinder.

If the master brake cilinder is leaking, you should have some pressure on the pedal, until the reservoir is empty.

If the pedal is broken you'll notice that, it will move different.

If the booster has no vaccuum of the membrane is shot, than it will brake, but you really have to stand on the pedal.

My money is on the booster or master brake cilinder.

Thank you!

It is not losing brake fluid. I pumped the pedal several times, as well as had my wife do this while I was watching/listening to the brake booster. It appeared to be blowing bubbles, or at least moving a lot of brake fluid in the reservoir while pumping.

If that is the case, than your master brake cilinder is gone. The booster is always dry. So if there is fluid inside the booster, than the cilinder is leaking. We had a case of that, last year. So I took of the vaccuum hose off the booster and used a copper wire as a dipstick and indeed fluid inside.

If that is not the case than the membrane is ripped and that is giving you your "bubbling noise".

So I would start on checking the inside of that booster and removing the master brake cilinder to assess that.

If your pedal goes to the floor, and the brake system is not leaking, defenetly the master brake cilinder is shot.

Yeah, but TS claims no loss of fluid, Rob. And, that I can not understand.

uwbuurman wrote: Sun Jun 19, 2022 1:58 pm Yeah, but TS claims no loss of fluid, Rob. And, that I can not understand.

If the cups needed for brake pressure are leaking (cups defect or cilinder scored) and the cups at the end are still sealing there is no fluid leak, and no brake pressure.

You can have exact the same symptom/problem with the clutch master cilinder.

Might be, but that is when the cilinder starts leaking into the booster. Anyway, we both think it will be the master brake cilinder, causing some problems.