Brake question

[andyshoun]

I drive an 86 NA. I replaced the brake master cylinder, soft brake lines and rebuilt the calipers four years ago. I rebuilt the front calipers and replaced the front rotors two years ago. I use Hawk and Carbotech brake pads. The car is a daily driver that sometimes gets to go to the track for DE events.

I recently noticed the brake pedal very slowly progressing to the floor. The brakes still stop great, but when I sit still (at a traffic light) with my foot on the pedal, the pedal will slowly creep lower and lower. A quick pump brings the pedal back up, but then it starts it's slow progression back to the floor.

Brake fluid level is good.

I assume that the master cylinder is the problem. I have ~ 50K miles of use on the last one. I just want someone to verify my prognosis.

[ernie9944]

first check what we commonly call the carpet cylinder (peel the rubber boot back #13) & see if there is fluid in there,if not check the plugs # 10 at the brake master cylinder they will deteriorate with time causing very small leaks which are hard to spot.This I know because at one time I had to change both (plugs/washer) on my 944.See diagrams