smartcarofamerica.com/threads/smart-fortwo-451-brake-bleeding.160203/

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Forum thread: smart Fortwo 451 Brake Bleeding | Smart Car of America Forum

smartcarofamerica.com/threads/smart-fortwo-451-brake-bleeding.160203/ · p. 1 · Applies to: 451

Source: smartcarofamerica.com Topic: brake bleeding after caliper upgrade Models discussed: 451 Solution status: unclear

Problem: After installing new four-piston calipers, rotors, pads, and braided brake hoses on a 2013 Smart Fortwo 451, the owner cannot achieve a firm brake pedal after multiple bleeding attempts. The pedal requires several pumps to become firm, indicating trapped air in the system, possibly including the ABS unit.

Solution: Multiple solutions were proposed: (1) Use a bi-directional scan tool to cycle the ABS unit during bleeding; (2) Try a vacuum brake bleeder with air compressor; (3) Slowly pump the brake pedal before opening bleeder screws; (4) Bleed both bleeder screws on four-piston calipers, ensuring they are positioned at the top of the calipers for proper air escape; (5) Tap the caliper with a soft-faced hammer to dislodge trapped air; (6) If air entered the ABS pump itself, use a pressure bleeder (Speedbleed) or MB Star diagnostic tool with special ABS pump bleeding procedure. Note: The original poster's four-piston calipers were installed with bleeder screws at the bottom instead of the top, which is improper for air bleeding.

Key facts: - User installed non-OEM four-piston calipers with bleeder screws positioned at the bottom of calipers rather than the top, which prevents proper air evacuation - Owner has iCarsoft scan tool with ABS bleeding capability but lacks equipment setup to bleed rear brakes first as required by the procedure - Air may have been introduced during brake hose replacement or if reservoir fluid level was allowed to drop below minimum - Traditional bleeding methods from pre-ABS vehicles may be insufficient for Smart Fortwo 451 which has ABS system requiring specialized procedures - Vacuum brake bleeders and pressure bleeders (Speedbleed) are recommended alternatives; if ABS pump itself contains air, MB Star diagnostic equipment may be required