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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 667 (ENGINE COOLING SYSTEM)REPAIR INSTRUCTIONSTHERMOSTAT BYPASS PIPES REPLACEMENTREMOVAL PROCEDURE
1999 GMC Forward Control 5.7 R, Automatic

Removal Procedure

1999 GMC Forward Control 5.7 R, AutomaticSECTION Removal Procedure
WARNING: This page is about a different car, the 2002 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.
  1. Drain the cooling system. Refer to Draining and Filling Cooling System .
  2. Remove the air cleaner intake duct. Refer to AIR CLEANER INTAKE DUCT .
  3. Remove the left engine mount strut. Refer to ENGINE MOUNT STRUT REPLACEMENT .
  4. Disconnect the left spark plug wires from the left spark plugs. Refer to
  5. Use the J 38185  in order to reposition the hose clamp from the water outlet housing.
  6. Remove the radiator inlet hose from the water outlet housing.
    7. Fig 1: Radiator Inlet Hose & Water Outlet Housing
    G01703869Courtesy of GENERAL MOTORS CORP.
  7. Remove the heater outlet hose (2) from the thermostat bypass pipe.
  8. Remove the throttle body inlet (3) and outlet (4) hoses from the thermostat bypass pipe.
    Fig 2: Heater Outlet Hose & Throttle Body Inlet & Outlet Hoses
    G01703870Courtesy of GENERAL MOTORS CORP.
  9. Remove the thermostat bypass pipe nut.
    Fig 3: Thermostat Bypass Pipe Nut
    G01703871Courtesy of GENERAL MOTORS CORP.
  10. Use the J 38185  in order to reposition the hose clamp from the thermostat bypass pipe.
  11. Remove the thermostat bypass pipe hose.
    12. Fig 4: Thermostat Bypass Pipe Hose
    G01703872Courtesy of GENERAL MOTORS CORP.
  12. Remove the thermostat bypass pipe bolt.
  13. Remove the thermostat bypass pipe.
    Fig 5: Thermostat Bypass Pipe & Bolt
    G01703873Courtesy of GENERAL MOTORS CORP.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.