Hard Brake Pedal Diagnosis - Subaru Outback 2020
The brake pedal is consistently hard to press, indicating a loss of power brake assist. This is likely due to a failed vacuum booster, a vacuum leak, or a faulty brake booster check valve. Immediate inspection is recommended to ensure safe stopping ability.
Diagnosis Details
Possible Causes
Failed brake booster (vacuum assist unit) - internal diaphragm leak or mechanical failure
Vacuum leak at booster hose or check valve - cracked hose or stuck valve
Faulty brake booster check valve - allows vacuum loss
Related OBD-II Codes
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What You Should Do
Inspect the brake booster vacuum hose and check valve for cracks or damage.
Test the check valve by blowing through it (should only allow flow one way).
If no external leaks, the brake booster itself is likely faulty and needs replacement.
Also check the vacuum supply from the engine (intake manifold).
Do not drive until repaired.
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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.
