Cooling system airflow

Engines have to maintain a balanced temperature, not too hot, and not too cold.

Also see the Engine-Cooling Page

Astro/Safari vans engine cooling system uses a clutched fan w/shroud to draw ambient air through the radiator while a water and antifreeze coolant mixture is pumped through the radiator, engine and heater core(s).

It's important to keep all of these components working properly together.

• • Antifreeze mixture - Keep full, the overflow tank is marked. Has additives to demin/distilled water to prevent freezing, lubricate the water pump, and resist corrosion. If you don't change it regularly, things will start to corrode from the inside out. I try to never use plain tap water, get demineralized/distilled water to mix with antifreeze, or buy premixed antifreeze. Now if you are flushing or an emergency, any water will be better than none.

  • Water pump - Has a weep hole at the bottom, occasional drip from here is not harmful, if it's leaking heavily or constantly, then the pump needs to be replaced. The gaskets between the pump and block are a common leakage point, gaskets should be installed dry.

  • Hoses - Make sure they are in good shape, no cracking or leaking.

  • Radiator - These can leak, esp when the antifreeze mixture has not been changed, causes corrosion from the inside. They can also be physically damaged or clogged, reducing airflow or causing a leak.

  • Clutched Fan - Usually the clutch will go bad in one of two ways. Either it will sound like a freight train because it's locked up, or it will get loose and cause the fan to spin at a slower RPM than designed. Many LAPS will have the tools to remove, often I just use a large adjustable with a mini sledge hammer. There are pneumatic tools that are the bees knees for removing, but are expensive as well. An air chisel on the corner of the nut can work wonders if you are replacing the water pump anyway.

  • There are upgraded thermal fan clutches that will spin the fan faster if you don't mind the extra energy they use and the noise they produce. Standard duty spins 60-70% of the shaft speed when engaged, 20-30% when disengaged. Heavy duty spins 70-90% engaged, 25-35% disengaged. Severe duty spins 80-90% engaged, 20-30% disengaged.

  • Radiator/Fan Shroud - Very important at low speeds as it increases fan airflow across the radiator fins, these crack or some people remove them to do work and never replace.

  • Modified bumpers - This can cause airflow issues to the radiator, esp large winch type bumpers. If your replacement bumper is higher or sticks out more than the original, it can cause airflow issues.

Coolant: Hint, color doesn't determine the type of coolant, each manufacturer chooses what dye to use, see below.