GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 2000 🢒 Alero 🢒 Engine 🢒 Engine Controls - 3.4L 🢒 Thermostat Diagnosis

Step

Action

Value(s)

Yes

No

1

Pressure check the cooling system and the cap for leaks. Repair any leaks before proceeding with the diagnosis. Four cylinder engines use an 82°C (185°F) T/STAT. Six cylinder engines use a 91°C (195°F) T/STAT.

Ambient temperatures should be between 13°-38°C (55°-100°F). Place the HVAC controls in the OFF position. Run a cold engine at idle (68°-70°F) for 15-20 minutes before checking the engine temperature.

Is the repair complete?

--

Go to Step 2

--

2

Verify the engine coolant temperature with a Scan Tool at idle.

Is the engine temperature below 85°C (185°F)?

--

Go to Step 5

Go to Step 3

3

Verify the engine coolant temperature with a Scan Tool at idle.

Is the engine coolant temperature between 85-96°C (185-205°F)?

--

System OK

Go to Step 4

4

Verify the engine coolant temperature with a Scan Tool at idle.

Is the engine coolant temperature over 96°C (205°F)?

--

Go to Step 7

--

5

Test the T/STAT for the following conditions:

    • The T/STAT is opening early
    • The T/STAT seal is leaking

Are either of these conditions present?

--

Go to Step 6

System OK

6

Replace the T/STAT and replace the T/STAT seal.

Is the repair complete?

--

System OK

--

7

Is the radiator inlet hot?

--

Go to Step 8

Go to Step 14

8
  1. Turn on the heater.
  2. Check for hot air at the heater outlets.

Is the air hot?

--

Go to Step 9

Go to Step 12

9

Inspect for blockage in the radiator.

Did you find any blockage?

--

Go to Step 10

Go to Step 11

10
  1. Repair the blockage.
  2. Reinspect the radiator with the Scan Tool .

Is the repair complete?

--

System OK

--

11
  1. Replace T/STAT.
  2. Inspect the radiator with the Scan Tool .

Is the repair complete?

--

System OK

--

12
  1. Rev the engine several times to remove any air.
  2. Inspect for blockage in the heater circuit.
  3. Inspect for pinched or buckled hoses.

Did you find any blockage?

--

Go to Step 13

Go to Heating Insufficient in Heating, Ventilation and Air Conditioning

13
  1. Repair the blockage.
  2. Reinspect the radiator with the Scan Tool .

Is the repair complete?

--

System OK

--

14

Air may be in the system.

  1. Add coolant to surge tank if low.
  2. Reinspect the radiator inlet hose.

Is the hose hot?

--

Go to Step 8

Go to Step 15

15

Inspect for blockage in the following locations:

    • The cylinder head
    • The radiator
    • The radiator hoses
    • The radiator nipples

Did you find any blockage?

--

Go to Step 16

Go to Step 17

16
  1. Repair the blockage.
  2. Reinspect the radiator with the Scan Tool .

Is the repair complete?

--

System OK

--

17
  1. Repair the T/STAT.
  2. Reinspect the radiator with the Scan Tool .

Is the repair complete?

--

System OK

--