Air in cooling system
Air in cooling system describes trapped air in the Pontiac Fiero cooling system.
Because the Fiero has a mid-mounted engine, a front-mounted radiator, and long coolant pipes running underneath the car, trapped air can cause cooling problems if the system is not filled and bled correctly.
Overview
Air in the cooling system can prevent coolant from circulating properly. It can also cause unstable temperature readings, coolant overflow, poor heater performance, or repeated overheating.
The Fiero cooling system is more sensitive to trapped air than many front-engine cars because the radiator and engine are separated by long coolant pipes.
Common causes
Air can enter the cooling system through:
- Coolant replacement
- Hose replacement
- Radiator replacement
- Water pump replacement
- Thermostat replacement
- Coolant leaks
- Low coolant level
- Incorrect filling procedure
- Bad radiator cap
- Bad thermostat cap
- Loose hose clamps
- Overheating and coolant overflow
Symptoms
Possible symptoms of trapped air include:
- Temperature gauge rises quickly
- Temperature readings fluctuate
- Coolant overflows from the reservoir
- Coolant level drops after cooling
- Gurgling sounds
- Poor coolant circulation
- Heater output changes
- Repeated overheating after service
- Cooling system seems full at one point but low later
Fiero-specific issues
The Fiero should usually be filled from the thermostat housing at the rear of the car, not only from the radiator at the front.
A slight nose-down position, with the front of the car lower than the rear, can help move trapped air toward the thermostat housing. This is not always required, but many owners find it helpful during filling and bleeding.
Related topics:
Diagnosis
If trapped air is suspected:
- Allow the engine to cool completely.
- Check the coolant level at the thermostat housing.
- Check the coolant reservoir level.
- Inspect for visible coolant leaks.
- Inspect the radiator cap and thermostat cap.
- Check for crushed or damaged coolant pipes.
- Refill and burp the system if needed.
- Monitor whether the coolant level remains stable after heat cycles.
If air keeps returning
A cooling system should not repeatedly collect air after it has been properly filled and burped.
If air keeps returning, check for:
- Coolant leaks
- Loose clamps
- Bad caps
- Damaged hoses
- Damaged coolant pipes
- Radiator leaks
- Water pump leaks
- Combustion gases entering the cooling system
Common mistakes
Common mistakes include:
- Filling only from the radiator
- Assuming the system is full after one fill
- Reinstalling the thermostat too early
- Opening the system while hot
- Ignoring crushed coolant pipes
- Ignoring cap problems
- Continuing to drive while overheating
Notes
Trapped air is a common cause of overheating after cooling-system service.
If the car overheats even after careful filling and burping, another cooling-system fault may be present.