Diagnosing a Mushy Brake Pedal on Our Skyline GTR

The brake pedal on my Skyline GTR never felt great. It was never firm at the top end like in my E92 BMW M3 or in Sean's Scion FR-S.

Instead, it was mushy until approximately half way through the pedal travel and then it would firm up, but required far more pressure than should be required to stop the car. The Ate Type 200 brake fluid and Power Stop pads were fresh. We bled air from the lines. The brake pedal still didn’t feel right. It had to be something else.

Steps Taken

To diagnose, we started the car to build vacuum pressure to the brake booster. Then, we shut off the engine. When all was quiet we listened closely and heard a hissing noise as the brake pedal was pressed. Air was escaping. We had a vacuum leak and are pretty sure it’s coming from the brake booster. It’s 25 years old and we’re not surprised it would be causing our brake pedal woes.

Now to source a new one. Wish us luck!