HYDRAULIC PUMP SHAFT FAILURES

What NHTSA is examining

The preliminary evaulation is being upgraded.during the ea odi will limitits investigation to only those vehicles equipped with a hydro-boost system, which provides power assist to the braking and steering sytems.vaccuum brake booster vehicles are excluded.odi hasexpanded the scope of the ea to include model years2003 and 2004, asduring the pe, odi learned that the hydroboast pumps were modified in febraury 2004.therefore,odi has expanded the scope to include the additional model years.odi's is concerned because thisisa sudden failure that affects two critical systems of the vehicle, brakes and steering, at the same time.the ability of the operator to handle the dual failures is a concern. Further, these vehicles tend to be work vehicles, with some over 10,000 pounds gvwr and many equipped to pull large trailers.dual failures of heavily loaded vehicles and vehicles pulling trailers further increases the safety risk.odi plans to conduct testing to quantify the braking and steering performance degradation and the impact on safe vehicle control, when a hydroboast pump fails.

Vehicles under investigation