Engine Overheating. Buick Roadmaster 1996

For 1990-2009 cars

## Engine Overheating Boiling; Poor Engine Cooling

#### Tools Required

tech 1 Scan Tool

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---

1

1. Allow the engine to cool.
2. Check for the proper coolant level.
3. Start the engine.
4. Monitor the engine coolant temperature using the tech 1 , or through the heater and A/C control assembly pointer number *-24. Refer to Climate Control Features in HVAC.

Important: The coolant flow may be interrupted at times because of the thermostat closing during engine warm-up.

5. Squeeze the radiator outlet hose by hand to check the coolant flow while monitoring the engine coolant temperature.

Is there coolant flow through the radiator assembly present at or before 100°C (212°F)?

--

Go to Step 2

Go to Step 3

2 | The condition is caused from something other than a faulty thermostat. Is there still an overheat or boiling condition? | -- | Go to Engine Overheating | --

3

1. Install a new engine coolant thermostat. Refer to Engine Coolant Thermostat Replacement .
2. Recheck the cooling system, using the tech 1 , in order to make sure the system is OK.

Is there still an overheat or boiling condition?

--

--

System OK

## Engine Overheating General

Step | Action | Value | Yes | No
--- | --- | --- | --- | ---
DEFINITION: The engine temperature lamp comes on and stays on, or the temperature gauge shows hot, or coolant overflows from the coolant recovery reservoir onto the ground while the engine is running.
1 | Check for a loss of coolant. Is there a loss of coolant? | -- | Go to Step 2 | Go to Step 3
2 | Fill the system to the specified level. Refer to Cooling System Draining and Filling . Does the engine still overheat? | -- | Go to Step 3 | System OK
3 | Check the engine oil level. Is the engine oil level too high? | -- | Go to Step 4 | Go to Step 5
4 | Correct the engine oil level as necessary. Does the engine still overheat? | -- | Go to Step 5 | System OK

5

Check for the following missing or damaged parts:

• | Radiator air side baffles

• | Radiator air lower deflector

• | Radiator air side baffles

• | Radiator fan upper and lower shrouds (RPO VO8 cooling system)

Are there any missing or damaged deflectors, baffles, or shrouds?

--

Go to Step 6

Go to Step 7

6

Repair or replace any deflectors, baffles, or shrouds as necessary.

• | For the air lower deflector, refer to Radiator Air Baffle Assemblies and Deflectors .

• | For the radiator air side baffles, refer to Radiator Air Baffle Assemblies and Deflectors .

• | For the air side deflectors, refer to Radiator Air Baffle Assemblies and Deflectors .

• | For the fan shrouds, refer to Fan Shroud Replacement .

Does the engine still overheat?

--

Go to Step 7

System OK

7 | Check the coolant concentration. Refer to Coolant Concentration Testing . Is the coolant concentration adequate? | -- | Go to Step 9 | Go to Step 8

8

Correct the coolant concentration as necessary. Refer to

Notice: Pure coolant can be added to raise the boiling point of the coolant, but too much will affect the freezing point. Do not use a solution stronger than 70 percent, as the freeze level rises rapidly after this point. Pure coolant will freeze at -22°C (-8°F).

.

Does the engine still overheat?

--

Go to Step 9

System OK

9 | Check for a loss of cooling system pressure. Does the cooling system maintain the correct pressure? | -- | Go to Step 11 | Go to Step 10
10 | Pressure test the cooling system. Correct as necessary. Refer to Cooling System Leak Testing . Does the engine still overheat? | 103 kPa (15 psi) | Go to Step 11 | System OK
11 | Check for a pinched or kinked coolant recovery reservoir hose. Is the reservoir hose kinked or damaged? | -- | Go to Step 12 | Go to Step 13
12 | Reroute or replace the hose as necessary. Does the engine still overheat | -- | Go to Step 13 | System OK
13 | Check the fan belt tension (RPO VO8 heavy-duty cooling system). Refer to Engine Mechanical. Is the fan belt tensioned properly? | -- | Go to Step 15 | Go to Step 14
14 | Correct the fan belt tension as necessary. Does the engine still overheat? | -- | Go to Step 15 | System OK
15 | Check for an exhaust system restriction (plugged catalytic converters). Is there a restriction in the exhaust system? | -- | Go to Step 16 | Go to Step 17
16 | Correct the restriction as necessary. Refer to Exhaust. Does the engine still overheat? | -- | Go to Step 17 | System OK
17 | Check for an obstructed radiator air flow or bent fins. Are any radiator fins bent or is air flow to the radiator being obstructed? | -- | Go to Step 18 | Go to Step 19
18 | Remove or relocate add on parts that block air flow to the radiator. Refer to Cooling System . Does the engine still overheat? | -- | Go to Step 19 | System OK
19 | Check for a blockage in the cooling system passages. Are the cooling system passages blocked? | -- | Go to Step 20 | Go to Step 21

20

1. Drain the coolant. Refer to Cooling System Draining and Filling .
2. Flush the cooling system. Refer to Flushing .
3. Repair as necessary.

Does the engine still overheat?

--

Go to Step 21

System OK

21 | Check for an inoperative cooling fan or a cooling fan operating in reverse (fan forcing hot air from engine compartment through the radiator). Are any cooling fans inoperative or operating in reverse? | -- | Go to Step 22 | Go to Step 23
22 | Refer to Emissions or reverse the polarity at the fan motor connector terminals. Does the engine still overheat? | -- | Go to Step 23 | System OK
23 | Check for an inoperative mechanical fan blade clutch (RPO VO8 heavy-duty cooling systems only). Is the fan blade clutch inoperative | -- | Go to Step 24 | Go to Step 25
24 | Replace the fan blade clutch. Refer to Fan Clutch Replacement . Does the engine still overheat? | -- | Go to Step 25 | System OK
25 | Check for an inoperative or damaged fan blade (RPO VO8 heavy-duty cooling system) or engine cooling fan. Is the fan blade/cooling fan damaged or incorrect? | -- | Go to Step 26 | Go to Step 27

26

1. Check for correct part number.
2. Replace the fan blade or cooling fan.

• | For the fan blade, refer to Fan Clutch Replacement .

• | For the cooling fan, refer to Electric Cooling Fan .

• | Does the engine still overheat?

--

Go to Step 27

System OK

27 | Check if the thermostat is stuck in the closed position. Refer to Engine Overheating . Is the thermostat sticking (or stuck) in the closed position? | -- | Go to Step 28 | Go to Step 29
28 | Replace the thermostat. Refer to Engine Coolant Thermostat Replacement . Does the engine still overheat? | -- | Go to Step 29 | System OK
29 | Check for a faulty coolant pump. Is the coolant pump faulty? | -- | Go to Step 30 | Go to Step 31
30 | Replace the coolant pump as necessary. Refer to Engine Mechanical. Does the engine still overheat? | -- | Go to Step 31 | System OK
31 | Check the radiator cooling capacity. Make sure the proper sized radiator is being used on the cooling system. Is the correct sized radiator being used with the cooling system? | -- | System OK | Go to Step 32
32 | If necessary, install the correct radiator. Refer to Radiator Replacement . Does the engine still overheat? | -- | -- | System OK