the steering became very hard. when i turned the engine off, power steering fluid squirted from under the reservoir cap. i drove the car 3 miles home and, during the drive it blew a seal on the rack and pinion assy. should i figure that a check valve or something on the pump went bad and replace both the pump and the rack-and pinion assy., or that the rack and pinion assy. went bad and the pump is still good?