1998 C70 230K, Went through a major maintenance cycle catch-up/repair/upgrade cycle last year. Control arms, end links, CV axles, brakes, brake lines, cooling system (ALL of it), timing belt, head gasket, engine bushings, ABS unit rebuild/replacement.

I've been getting some funkiness from my brakes and I'm not sure if this is a strange master cylinder problem, booster, or something else.

My main symptom is occasional "Stiff" brake pedal. Hard resistance at pedal, pedal very high. Car stops fine, but tend to "release" a bit once nearly or completely stopped. If it releases after I stop, the car will roll about a foot before the pads catch it... which is scary. The symptoms are mainly as described. I don't get "squishy" brakes or soft pedal. Brake are definitely working. But this stiff/release bit has got me concerned.

I initially feared it was a failing MC and I ordered a replacement ATE unit as soon as the strangeness appeared. I have not installed it because I'm now wondering if this is something vacuum related (booster, hose, or check valve), or perhaps something related the ABS unit.

I hate shotgunning money at problems, but with high miles, and an unknown number of years of neglected maintenance, many things have worn out.

Any thoughts?