I am recently (last few weeks) noticing some symptoms which I can not fully explain. I hope that I can get some help here. It relates to my "Japanese SPI" Mini. Earlier this year (Feb ~ April) I replaced the brake components near all wheels: new hoses, refurbished the calipers, new rotors, new rear slave cylinders and new brake shoes. The brake master (GMC90376) and brake servo (GSM119) appeared to be good so I did not replace these. The vacuum hose with integrated non-return valve looked not so good, so I replaced it with new hose and a separate non-return valve (17H2646). Adjusted the hand brake cables at the rear wheels. Then filled the system with new brake fluid and did a proper bleeding procedure. This resulted in proper brake function.
What I am noticing lately is a difference in behaviour between a "firm step your foot on the pedal" and a "gentle touch on the pedal". With the engine off the effect is the same in both cases: the pedal travel is short and results in firm pressure (can't push any further). When the engine is running I notice a difference in behaviour: when I step firmly on the pedal it behaves the same as when the engine is off: the pedal travels only a short distance and then can not be pushed any further. However, if I push the pedal gently, or use one finger to push the pedal, I can push the pedal down all the way to the floor.
I can't really explain what is causing this effect? The difference between engine running and engine off is the presence/absence of vacuum to the brake servo. But, if there is a vacuum leak I would expect the pedal to, eventually, go to the floor in all cases. Thus also when I push hard on the pedal. This isn't happening. Alternatively, if a seal in the brake master would be leaking I would assume that I would observe the same behaviour both with engine off, and with running engine.
What am I overlooking? What could be a possible root cause for this behaviour?
Edit: I forgot to mention in my initial post that there is no leakage of brake fluid. The fluid level in the master reservoir is stable since all this time. The connections at all hoses are dry, as are the connections at the master cylinder.
Edited by NLinPEN, Today, 02:44 AM.
