Hard Brake Pedal Diagnosis - BMW 3 Series 2019
A consistently hard brake pedal indicates a loss of power brake assist, likely due to a failed brake booster, vacuum leak, or faulty booster check valve. This significantly increases stopping distance and poses a safety risk.
Diagnosis Details
Possible Causes
Failed brake booster (vacuum assist unit) - internal diaphragm leak or mechanical failure
Vacuum leak in the hose or check valve between intake manifold and brake booster
Faulty brake booster check valve (allows vacuum to escape)
Brake booster vacuum pump failure (if equipped with diesel or certain turbo engines)
Related OBD-II Codes
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What You Should Do
Do not drive the vehicle until repaired.
Check the brake booster vacuum hose and check valve for cracks or disconnection.
Test brake booster function by pumping brake pedal with engine off, then start engine; pedal should drop slightly.
If no change, booster or vacuum supply is faulty.
Replace booster, hose, or check valve as needed.
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Disclaimer: This AI-generated diagnosis is for informational reference only. Always consult a qualified mechanic for an in-person inspection. AutOwner is not responsible for decisions made based on this information.
