| Subject: | Hydro-Boost Brake Pedal Moves Or Self Applies At Full Turns |
| Models: | 1988-2006 All Full Size Chevrolet Trucks and Utilities |
| 1988-2005 Chevrolet Astro Vans |
| 1988-2006 Chevrolet G Vans (including Express) |
| 1988-2006 All Full Size GMC Trucks and Utilities |
| 1988-2006 GMC G Vans (including Savana) |
| 1988-2005 GMC Safari Vans |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
On vehicles with hydro-boost, customers may notice during full lock turns or near full lock turns that the brake pedal will move down or self apply. This can be caused by the internal dump valve of the hydro-boost not seating properly due to contamination
in the steering system. The hydro-boost assembly is not tolerant to certain types of contaminates that may be present in the steering system.
Recommendation/Instructions:
The Hydro-boost system is not serviceable, and must be replaced. Before replacement of the hydro-boost system, the entire steering system (power steering pump, lines, and the gear box) must be flushed to avoid reoccurrence.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
