What Causes the Upper Radiator Hose to Be Hot While the Lower Hose Remains Cold?
2 Answers
The reason the upper radiator hose is hot while the lower hose remains cold is due to a faulty thermostat that fails to open or air pockets in the cooling system, which disrupt the coolant circulation. Faulty Thermostat: If you plan to remove the thermostat, you should block the small coolant circulation loop to ensure all coolant flows through the radiator for cooling. Vehicle cooling systems utilize a combination of air and liquid cooling, where engine heat is transferred to the radiator via coolant, and then dissipated by natural airflow and the cooling fan. Air Pockets in the Cooling System: If the connection between the cooling system's antifreeze reservoir and the radiator is not tightly sealed, it can lead to coolant leakage.
I think it's quite common for the upper radiator hose to be hot while the lower one remains cold. I've encountered this issue several times myself. First, it could be a faulty thermostat, which controls the circulation of coolant between the engine and the radiator. If it gets stuck and doesn't open, hot coolant can't flow into the lower hose for cooling, causing it to stay cold. Second, a problem with the water pump can also cause this. The pump drives the coolant flow, and if it fails, the coolant won't circulate properly, leaving the lower hose cool. Additionally, low coolant levels or air bubbles blocking the system are potential causes. If left unrepaired, prolonged localized overheating can lead to engine deformation or even a blown head gasket, so don't delay. Check the coolant level and temperature gauge immediately, and if necessary, visit a professional repair shop to replace the thermostat or inspect the water pump. Regular maintenance, such as monitoring the antifreeze condition, can help prevent such issues.
