GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 Rendezvous - FWD 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Engine Overheating

Step

Action

Yes

No

DEFINITION: Either of the following conditions indicate a probable engine overheat condition.

    • The engine temperature gauge is in the red (overheat) zone and/or the engine temperature indicator is ON.
    • Hot engine coolant overflows from the coolant recovery reservoir and/or radiator cap onto the ground while the engine is running.

1
  1. Inspect and fill the cooling system as necessary. Refer to Cooling System Draining and Filling .
  2. Inspect the cooling system for leaks as necessary.
  3. Repair the cooling system leaks as necessary.

Has the inspection/repair been performed?

Go to Step 2

--

2
  1. Start the engine and allow the engine to run at approximately 1200 RPM.
  2. Use the Scan Tool in order to verify the overheat condition.

Does the Scan Tool verify the engine overheat condition?

Go to Step 3

Go to Engine Coolant Temperature Gage Inaccurate or Inoperative in Instrument Panel, Gauges and Console

3
  1. Verify that the cooling fans are operating properly.
  2. Repair the cooling fan system as necessary.

Does the engine still overheat?

Go to Step 4

System OK

4

Perform the following inspections:

    • Inspect the radiator and the A/C condenser cooling fins for debris or any other obstruction.
    • Inspect the drive belt system and the drive belt tensioner for proper operation in order to ensure that the coolant pump is rotating properly.
    • Inspect for a loose, damaged, and/or missing air deflector(s). Refer to Radiator Air Baffle Assemblies and Deflectors .
    • Check for a pinched or kinked cooling system hose.
    • Repair the systems as necessary.

Does the engine still overheat?

Go to Step 5

System OK

5

Caution: As long as there is pressure in the cooling system, the temperature can be considerably higher than the boiling temperature of the solution in the radiator without causing the solution to boil. Removal of the pressure cap while the engine is hot and pressure is high will cause the solution to boil instantaneously -- possibly with explosive force -- spewing the solution over the engine, fenders and the person removing the cap.

Inspect the thermostat for proper operation. Refer to Thermostat Diagnosis .

Is the thermostat operating properly?

Go to Step 7

Go to Step 6

6

Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .

Does the engine still overheat?

Go to Step 7

System OK

7

    Important: Excessive coolant freeze point protection MAY cause the coolant to boil at low temperatures.

  1. Inspect for the proper coolant concentration (mixture). Correct the coolant concentration as necessary.
  2. Remove the radiator cap.
  3. Start the engine and inspect for a steady and constant flow of air bubbles in the engine coolant.

Is there a steady and constant flow of air bubbles in the engine coolant?

Go to Step 8

Go to Step 9

8

The probable cause of the engine overheat is combustion chamber gasses leaking into the cooling system. This condition is usually caused by the following:

    • A faulty cylinder head gasket
    • A faulty cylinder head
    • A faulty engine block

Verify this condition by using spark plug electrodes or the porcelain surrounding the spark plug electrodes that exhibit signs of coolant. Replace the engine internal component(s) as necessary in order to repair the engine internal coolant leak.

Does the engine still overheat?

Go to Step 1

System OK

9

The engine overheat may be caused by a cooling system blockage. Flush the cooling system. Refer to Flushing .

Does the engine still overheat?

Go to Step 10

System OK

10

Important: It is VERY unlikely that the water pump is the cause of the overheat condition.

If NONE of the cooling system passages are restricted, replace the coolant pump. Refer to Water Pump Replacement .

Does the engine still overheat?

Go to Step 1

System OK