Thread: Soft Brake Pedal

So the other day i drove over to my parents house brakes where fine. On the way home stopped at 3 traffic lights brakes were also fine, then had to slow down for a turn and the pedal was soft and only had brakes at the very bottom of the pedal and minimal braking at that. So i nursed it home ( was only a few blocks away) and checked the fluid, it was full. No leaks anywhere, vacuum lines all appear to be fine.

Master Cylinder was replaced in Feb 2018 along with all new steel braided brakes lines, pad and rotors and they have been brilliant ever since.

Atm it has pedal it just super soft and spongy, pedal returns to the top without help. Pedal is spongy with the car on or off. I put the nanocom on it had zero faults. Just after some ideas, to me it seems like it needs a bleed but just seems odd to work for years than just play up like this without leaks ect.

I posted in an earlier thread about my ABS modulator failing which created the exact opposite condition i.e. the brakes looked on and stayed locked on for the two weeks it took me to organise and install a replacement modulator. Caused by a shonky seller "forgetting" to mention he'd put something in the brake fluid other than brake fluid. Even though he'd rebuilt all the calipers and installed a new master cylinder and flushed the fluids, this had also caused the modulator seals to swell and jam the first time traction control kicked in. Considering there's 8 valves in the D2 modulator, this was no mean feat.

Oil in the brake fluid is a very potent destroyer of seals. I've since replaced the clutch cylinders and the master cylinder was obviously replaced before the flush as it's dicey now too. Fortunately I had the PO supply a replacement for this.

The modulator is easy to diagnose, just crack the unions to the calipers at the modulator one a t a time and see if there is pressure there when the pedal is pressed. If not, you've found the culprit and if there is it's the rubber hoses and/or calipers.