How Much Coolant Should Flow Out of the Upper Radiator Hose?

Before the Thermostat Opens

As long as the engine is running and the belt is turning the water pump, a small amount of coolant will flow from the upper radiator hose. Until the engine warms up, and the thermostat opens, this will be a small stream.

When the Thermostat Opens

When the thermostat opens, there should be a steady flow of coolant from the hose. Even with the hose still attached to the thermostat housing, pressure should be felt in the upper hose by attempting to squeeze it.

Bottom Line

The flow from the upper hose should be checked on a relatively warm engine with the thermostat open. If the flow is a mere trickle there is not enough coolant in the system, a leak in the system or a faulty water pump.

References

• No Reference Needed

Resources

• Autohaus: Cooling System Parts