BRAKE BOOSTER CHECK VALVE FAILS CAUSING VAC HOSE FEEDING TO BOOSTER UNIT TO BECOME TOTALLY SEPARATED FROM VALVE. RESULT IS NO BRAKE ASSIST. THIS HAPPENED TO ME IN MY 2001 AUDI S4!!!! AT HIGHWAY SPEED! *JB
2001 Audi S4
Owner reports · Recalls · Investigations
Limited comparison data
There is not enough comparable history to draw a useful model-year comparison.
About this comparison →How this year compares
Owner complaints by model year
Compare all S4 years →Counts vary with age, sales and reporting. They are not failure rates.
What owners reported most
All reported categories
Tap a category to read its complaints. One report may name several components.
When problems were reported
Mileage at the reported incident
54 reports with mileage · 33 unknown
NHTSA’s mileage field refers to the reported incident, not necessarily the filing date. This shows report counts, not the likelihood of a failure.
What to inspect
Issues worth paying extra attention to based on owner reports.
- Electrical System. Review the 47 owner reports in this category and discuss these concerns during a pre-purchase inspection. Read reports →
- Engine And Engine Cooling. Review the 11 owner reports in this category and discuss these concerns during a pre-purchase inspection. Read reports →
- Tires. Review the 10 owner reports in this category and discuss these concerns during a pre-purchase inspection. Read reports →
NHTSA owner reports · September 18, 2026 snapshot.
Service Brakes, Hydraulic complaints
2 reports1) CAR IS 2001 AUDI S4 AVANT. CAR WAS RUNNING FOR APPROXIMATELY 15 MINUTES, AND WAS IDLING AT TOP OF DRIVEWAY FOR ABOUT 5 MINUTES WITH PARKING BRAKE ENGAGED WHILE OTHER CAR IN FRONT WAS BEING MOVED. UPON RELEASE OF PARKING BRAKE REGULAR BRAKES FAILED, RESULTING IN CAR ROLLING DOWNHILL, ABOUT 30 FEET, FROM A STANDING START A…
Read full complaint
1) CAR IS 2001 AUDI S4 AVANT. CAR WAS RUNNING FOR APPROXIMATELY 15 MINUTES, AND WAS IDLING AT TOP OF DRIVEWAY FOR ABOUT 5 MINUTES WITH PARKING BRAKE ENGAGED WHILE OTHER CAR IN FRONT WAS BEING MOVED. UPON RELEASE OF PARKING BRAKE REGULAR BRAKES FAILED, RESULTING IN CAR ROLLING DOWNHILL, ABOUT 30 FEET, FROM A STANDING START AND COLLIDING WITH A PARKED CAR. BRAKE PEDAL SHOWED NO RESISTANCE OTHER THAN MILD SPRING PUSH-BACK, AND WAS PUSHED DOWN TO FLOOR. A BRAKE PEDAL WAS PUMPED WITH NO RESULT. SAME BRAKE CONDITIONS WERE REPEATED IMMEDIATELY AFTER COLLISION AND OVER A CONTINUING PERIOD OF MINUTES WITH IDENTICAL RESULTS, DURING WHICH TIME I EXITED AND RETURNED TO CAR ON MULTIPLE OCCASIONS. FINALLY, AFTER APPROXIMATELY 5 MINUTES FOLLOWING THE ACCIDENT BRAKES RESUMED FULL AND NORMAL FUNCTIONING. CAR WAS IDLING THROUGHOUT THIS TIME PERIOD WITHOUT INTERRUPTION. AIR BAGS DID NOT DEPLOY . 3) REPORTED TO DEALER MOHEGAN LAKE MOTORS) ON 1/16 AND TO AUDI AMERICA ON SAME OR NEXT DAY. CAR TOWED TO DEALER ON 1/17. AUDI AMERICA REPORTED LATER THAT THEY HAD NO KNOWLEDGE OF ANY SIMILAR OCCURRENCES OR ISSUES CONCERNING BRAKES - ALSO BEGAN INQUIRY ON WHY AIR BAGS DID NOT DEPLOY , BUT I DID NOT PURSUE THIS DURING OUR DISCUSSIONS SINCE THERE WERE NO INJURIES. DEALER REPORTED ON 1/24 THAT THEY WERE UNABLE TO DUPLICATE THE PROBLEM, AND HAD NO ANSWER FOR THE BRAKE FAILURE, AND WERE TAKING NO CORRECTIVE ACTIONS. AUDI AMERICA REPORTED ON 1/25 THEY WERE TAKING NO FURTHER ACTION AND MAKING NO FURTHER INQUIRIES. *AK
Official recalls
121V470000 · Air Bags:frontal:driver Side:inflator Module
Jun 23, 2021
Volkswagen Group of America, Inc. (Volkswagen) is recalling certain 2000-2001 Audi TT Coupe, TT Roadster, 2000-2002 A4, and S4 vehicles equipped with Non-Azide Driver Air Bag Inflators (NADI) that do not contain phase stabilized ammonium nitrate (PSAN) propellant. Due to a manufacturing issue, the NADI inflators may absorb moisture, possibly causing the air bag to deploy improperly in the event of a crash.
Consequence & remedy
Consequence: In the event of a crash necessitating air bag deployment, the air bag may not properly protect the occupant, increasing the risk of serious injury or death.
Remedy: Dealers will replace the driver frontal airbag inflator with an alternative inflator, free of charge. Owner notification letters were mailed November 2, 2021. Owners may contact Audi customer service at 1-800-253-2834. Volkswagen's number for this recall is 69CJ.
Model-level recall history does not show whether a particular VIN is affected or has received a repair. Check a VIN with NHTSA ↗
NHTSA investigations
0No exact-year investigations in this snapshot.
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