Steering: hydraulic power assist system
- Component
- Steering: hydraulic power assist system
- Manufacturer
- THOMAS BUILT BUSES, INC.
- Vehicles affected
- 1,150
- Reported to NHTSA
- 1994-08-01
- Owners notified
- 1994-10-17
Defect description
A SUDDEN HYDRAULIC PRESSURE LOSS DURING HARD TURNS RESULTS IN A MOMENTARY LOSS OF POWER STEERING ASSIST. THE PRESSURE LOSS OCCURS WHEN THE HYDRAULICALLY DRIVEN ENGINE COOLING FAN TURNS OFF IN THE TURN.
Safety risk
THE DRIVER REACTS TO THE LOSS OF POWER STEERING ASSIST BY OVERSTEERING, WHICH COULD RESULT IN A VEHICLE ACCIDENT.
Manufacturer remedy
THE HYDRAULIC CONTROL VALVES WILL BE REPLACED WITH VALVES OF A NEW DESIGN. UNTIL SUCH TIME AS PARTS ARE AVAILABLE, OWNERS WILL BE INSTRUCTED TO DISCONNECT THE FAN CUTOFF SWITCH SO THAT HYDRAULICALLY DRIVEN FANS WILL RUN FULL TIME, ELIMINATING THE PRESSURE SPIKE.