Heating Performance

2004 Oldsmobile Bravada AWDSECTION Heating Performance
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.
WARNING: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.
  1. If sent here from Too Cold In Vehicle test, go to next step. If not sent here, see TEST H: TOO COLD IN VEHICLE  under SYMPTOM TESTS.
  2. Start engine and allow to idle. If engine reaches normal operating temperature, go to next step. If engine does not reach normal operating temperature, go to step  9.
  3. Allow engine to idle. Select FLOOR mode, minimum blower speed, and maximum temperature setting. Feel temperature of inlet and outlet hoses at heater core. If inlet hose feels warmer than outlet hose, go to step  7. If inlet hose does not feel warmer than outlet hose, go to next step.
  4. Install thermometer into center instrument panel air outlet. Select VENT mode, maximum blower speed, and maximum temperature setting. Record temperatures at center instrument panel air outlet and heater core outlet hose. If temperatures are similar, go to next step. If temperatures are not similar, go to step  6.
  5. Inspect cowl, recirculation door and HVAC module case for cold air leaks. If leaks are found, repair as necessary. When repairs are complete, go to step  10.
  6. Check temperature door operation. If problem is found, repair as necessary. When repairs are complete, go to step  10.
  7. Turn engine off. Back-flush heater core. Start engine. Select FLOOR mode, minimum blower speed, and maximum temperature setting. Feel temperature of inlet and outlet hoses at heater core. If inlet hose feels warmer than outlet hose, go to next step. If inlet hose does not feel warmer than outlet hose, go to step  10.
  8. Replace heater core. See HEATER CORE  under REMOVAL & INSTALLATION.
  9. Repair cause of low engine temperature concern. See appropriate ENGINES or ENGINE COOLING article.
  10. Operate system to verify repair. If system operates correctly, system is okay. If system does not operate correctly, go to step  2.
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.