One problem related to power assist brake vacuum has been reported for the 1997 Mercury Cougar. The most recently reported issues are listed below.
While traveling 30mph in traffic started applying brakes to slow down, had no brakes, and vehicle kept going. Brake pedal was almost to the floor. Also, cruise control had failed. Stopped vehicle and had it towed to mechanic. Was informed that brake booster plunger, had worn out, causing non braking ability.