Last Updated on: 7th September 2023, 12:38 am
The radiator is connected to the engine via two hoses; the top and bottom radiator hose.
These hoses are responsible for circulating coolant through the engine to dissipate heat. It’s common for the top radiator hose to be hot while the bottom radiator hose is cool.
In this article, I’ll explain why the top radiator hose may be hot while the bottom radiator hose is cold and what it means.
Should Both Upper and Lower Radiator Hoses Be Hot?
Ideally, when the engine is fully heated and operational, both the upper and lower radiator hoses should feel warm to the touch.
This signifies that the coolant is circulating without any obstruction throughout the system, ensuring the engine receives the right amount of cooling.
- The top radiator hose allows hot coolant from the engine block to flow into the radiator and through the core.
- The bottom radiator hose allows cooled coolant to flow back through the engine.
- When the engine is cold and has just started, you’ll notice both radiator hoses may be cool, the top hose will warm up faster than the bottom hose.
It is typically normal to find the upper radiator hose warmer than the lower one.
Should the Bottom Radiator Hose Be Hot?
The bottom radiator hose should be warm to the touch, but not hot. This indicates that the coolant is flowing through the cooling system and the coolant is being cooled properly.
However, if the bottom radiator hose is hot to the touch, it could mean that there is a blockage in the cooling system or a problem with the water pump or the radiator.
Should the Top Radiator Hose Be Hot?
The top radiator hose should be hot to the touch when the engine is fully warmed up and running. This is because it is flowing hot coolant from the engine into the radiator.
If the top radiator hose is cool, it could mean that there is a problem with the coolant flow or a malfunctioning thermostat.
A cold top radiator hose can also indicate a problem with the water pump or a blockage in the coolant system and passages.
How Do I Know if My Water Pump Is Circulating?
To check if the water pump is circulating, simply find and carefully feel the top radiator hose.
- If the top radiator hose is hot to the touch, the water pump is likely circulating properly.
- If the top radiator hose is cool, it could indicate a problem with the water pump or a blockage in the cooling system.
Other signs that the water pump may not be working include a decrease in coolant level, a low reading on the temperature gauge, or a warning light on the dashboard.
What Does It Mean if Both Radiator Hoses Are Hot?
If both the top and bottom radiator hoses are hot, it could indicate a problem with the thermostat or it could be normal operation of the engine.
The thermostat controls the flow of coolant through the engine and, when malfunctioning, can cause coolant to flow through the system even when the engine is cold, resulting in both radiator hoses to be hot.
However, if the engine is fully warmed up, both the top and bottom radiator hose should be be hot or warm to the touch, this signifies proper coolant flow through the thermostat and radiator.
The top radiator hose should be hot to the touch, while the bottom radiator hose should be warm but not overly hot.
If both hoses are hot, it could indicate a problem with the thermostat. Other possible causes include a blockage in the system, a problem with the water pump, or a lack of coolant.
It is important to regularly check the temperature of your radiator hoses and address any issues as soon as they arise. Regular maintenance and inspections can help to prevent serious problems and prolong the life of your vehicle’s engine.
A very hot to the touch upper radiator hose is likely caused by a blockage somewhere in the cooling system, typically somewhere around the radiator.
Usually the lower radiator hose should be colder than the upper radiator hose. However, they could feel like they’re the same temperature to the touch.
Your engine will overheat if the radiator is blocked and not circulating coolant. Your vehicles dashboard should display a warning that coolant temperature is too hot.