GM Full-Size Trucks 1988-1998 Repair Information

Hydro-Boost

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Diesel engine trucks and some 30/3500 series trucks and motor home chassis are equipped with the Bendix Hydro-boost system. This power brake booster obtains hydraulic pressure from the power steering pump, rather than vacuum pressure from the intake manifold as in most gasoline engine brake booster systems.

REMOVAL & INSTALLATION




CAUTION
Power steering fluid and brake fluid cannot be mixed. If brake seals contact the steering fluid or steering seals contact the brake fluid, damage will result!

  1. Turn the engine off and pump the brake pedal 4 or 5 times to deplete the accumulator inside the unit.
  2.  
  3. Tag and disconnect the hoses from the booster.
  4.  
  5. Unfasten the master cylinder retainers, and remove the cylinder keeping the brake lines attached. Secure the master cylinder out of the way.
  6.  
  7. Unplug all necessary electrical connections.
  8.  
  9. Unfasten the pushrod retainer and disconnect the pushrod from the brake pedal, in some cases it will be easier to remove the brake light switch to access the pushrod retainer.
  10.  
  11. Remove the booster unit from the firewall.
  12.  
  13. Remove the gasket.
  14.  

To install:

Installation is the reverse of removal, but please note the following important steps.

  1. Always install a new gasket.
  2.  
  3. Tighten the booster mounting nuts to 22 ft. lbs. (30 Nm) on all except 1996-98 models and 26 ft lbs. (36 Nm) on 1996-98 models.
  4.  
  5. After installation is complete, bleed the Hydro-Boost system.
  6.  

 
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