Hi,

I just want to share my experience regarding a leaky brake booster to you all!

Ever since I bought my -89 745 GLT two years ago, my brake system has been suffering from all the symptoms of a leaky brake booster. The pedal has been feeling hard and it presses against my foot when I turn the engine off. First, I checked the check valve (pun unintended) and the vacuum hose and found them being in order. Therefore, I assumed that the brake booster must be bad.

I was thinking of an earlier FAQ phrase saying "take a second mortgage" in order to buy a new booster when I got the tip that there is an o-ring between the master cylinder and the booster. Or rather, should be...

When I removed the master cylinder I noticed that the o-ring was missing! Some mechanic(?) must have had a bad day...

However, I took a suitable o-ring (about 5 cm in dia) from my good-to-have o-ring kit and mounted it where there should have been one from the beginning. Et voilà, the brake system was as good as new again!!

In my case it was quite obvious that there was a leak since the o-ring was missing, but I guess that an old, cracked o-ring could result in the same symptoms as well.

So, check that o-ring before you take that second mortgage!