GM S10/S15/Sonoma Pick-Ups 1982-1993 Repair Manual

Component Replacement

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SYSTEM FILLING



The master cylinder reservoirs must be kept properly filled to prevent air from entering the system. No special filling procedures are required because of the anti-lock system.

When adding fluid, use only DOT 3 fluid; the use of DOT 5 or silicone fluids is specifically prohibited. Use of improper or contaminated fluid may cause the fluid to boil or cause the rubber components in the system to deteriorate. Never use any fluid with a petroleum base or any fluid which has been exposed to water or moisture.

EHCU MODULE



See Figures 1 and 2

The EHCU module is not serviceable and must never be disassembled or repaired. If tests indicate the unit is faulty, the entire assembly must be replaced.

  1. Tag and disconnect the brake lines from the bottom of the combination valve. Plug the openings to prevent brake system contamination or excessive fluid loss.
  2.  
  3. Detach the combination valve electrical connector.
  4.  
  5. Tag and disconnect the brake lines from the EHCU. Immediately cap or plug all openings to prevent system contamination or excessive fluid loss.
  6.  
  7. Tag and disengage the electrical connectors from the EHCU.
  8.  



Click image to see an enlarged view

Fig. Fig. 1: Electro Hydraulic Control Unit (EHCU) mounting



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Fig. Fig. 2: EHCU brake pipe connections-ALWAYS tag the connections to assure proper installation

  1. Unfasten the retainers holding the EHCU upper bracket to the lower bracket and vehicle. Remove the upper bracket and hydraulic unit as an assembly.
  2.  
  3. If necessary, once they are removed from the vehicle, separate the bracket from the EHCU.
  4.  

To install:
  1. If removed, assemble the EHCU to its bracket. Install the retainers and tighten to 60 inch lbs. (7 Nm). Be careful as overtightening these bolts can cause excessive noise transfer during system operation.
  2.  
  3. Install the assembly into the vehicle, then tighten the retainers to 33 ft. lbs. (45 Nm).
  4.  
  5. Engage the electrical connectors as tagged during removal. Make certain each is squarely seated and secure.
  6.  
  7. Remove the caps or plugs, then connect the brake lines to their original locations, as tagged during removal. Tighten the fittings to 16 ft. lbs. (25 Nm).
  8.  
  9. Attach the electrical connector to the combination valve, then unplug and attach the brake lines to the bottom of the combination valve. Tighten the brake line fittings to 15 ft. lbs. (20 Nm).
  10.  
  11. Properly bleed the hydraulic brake system, including the EHCU module.
  12.  

FRONT WHEEL SPEED SENSORS



See Figure 3



Click image to see an enlarged view

Fig. Fig. 3: Front wheel speed sensor/splash shield assembly mounting

  1. Raise and support the front of the vehicle safely using jackstands.
  2.  
  3. Remove the tire and wheel assembly.
  4.  
  5. Remove the brake caliper from the mounting bracket and support aside from the suspension using a coat hanger or wire. Make sure the brake line is not stretched, kinked or otherwise damaged. The line should NEVER support the weight of the caliper.
  6.  
  7. Remove the brake rotor/disc (please refer to the procedure earlier in this section), then remove the hub and bearing assembly. For details on hub and bearing removal, please refer to the steering knuckle procedure in Chapter 8 of this manual.
  8.  
  9. Disengage the sensor wiring connector.
  10.  
  11. Disconnect the sensor wire from the clip(s) on the upper control arm. On most vehicles this will involve removing the retaining bolt/nut in order to free the clip, then separating the wire from the clip.
  12.  
  13. Remove the splash shield retaining bolts, then remove the shield and sensor assembly.
  14.  

To install:
  1. Mount the sensor and splash shield assembly to the steering knuckle. Install the retaining bolts and tighten them to 11 ft. lbs. (15 Nm).
  2.  
  3. Connect the wiring to the clip(s) on the upper control arm. Check the wiring for correct routing. If removed, install and tighten the clip retaining bolt/nuts, refer to the illustrations for locations and torque specifications. The wiring on some vehicles/components may be marked at the appropriate clip mounting position, look for a paint stripe on the sensor wire.
  4.  
  5. Engage the wiring connector.
  6.  
  7. Install the hub and bearing assembly.
  8.  
  9. Install the brake rotor (disc).
  10.  
  11. Remove the support, then reposition and secure brake caliper.
  12.  
  13. Install the tire and wheel assembly.
  14.  
  15. Remove the jackstands and carefully lower the vehicle.
  16.  

REAR WHEEL SPEED SENSORS



See Figures 4 and 5



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Fig. Fig. 4: Rear wheel speed sensor-MFI-Turbo



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Fig. Fig. 5: The rear wheel speed sensors are secured by two retaining bolts

  1. Raise and support the rear of the vehicle safely using jackstands.
  2.  
  3. Remove the tire and wheel assembly.
  4.  
  5. Matchmark and remove the brake drum.
  6.  
  7. Remove the primary brake shoe. For details, please refer to the brake shoe procedure located earlier in this section.
  8.  
  9. Disengage the sensor wiring at the connector.
  10.  
  11. Remove the sensor wire from the rear axle clips.
  12.  
  13. Unfasten the 2 bolts holding the sensor to the brake backing plate, then remove the sensor by carefully tracking the wire through the hole in the backing plate.
  14.  

To install:
  1. Route the wire through the hole in the backing plate and fit the sensor into position.
  2.  
  3. Install the retaining bolts and tighten to 26 ft. lbs. (35 Nm).
  4.  
  5. Secure the sensor wire within the rear axle clips.
  6.  
  7. Engage the sensor wiring to the harness connector.
  8.  
  9. Install the primary brake shoe.
  10.  
  11. Align and install the brake drum.
  12.  
  13. Install the tire and wheel assembly, then remove the jackstands and carefully lower the vehicle.
  14.  

 
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