6 Causes of a Cold Lower Radiator Hose (and How to Fix It)
If you have a problem with coolant temperature and find that the lower radiator hose is cold instead of hot, you may have cooling system problems that need repair.
You will need to look at the various parts that influence radiator temperature to properly diagnose a cold lower radiator hose problem.
So what causes the lower radiator hose to stay cold?
The most common reasons for a cold lower radiator hose are a faulty thermostat, faulty water pump, or low coolant level. It can also be caused by air pockets or a clogged cooling system.
Here is a more detailed list of the 6 most common causes of a cold lower radiator hose:
6 Causes of a Cold Lower Radiator Hose
1. Faulty thermostat
This is the most common problem when dealing with a cold lower coolant hose. The engines are equipped with a valve thermostat that determines and regulates the coolant supply so that the engine runs at an optimal temperature and does not overheat.
If your car overheats and at the same time does not heat the lower coolant pipe, you probably have a problem with your thermostat, which needs to be replaced.
The thermostat should be closed when the engine is cold and not running. Thermostatic water regulation prevents hot spots in the engine. Once the optimal temperature is reached, cooling water will be introduced into the radiator for energy dissipation.
If the thermostat does not open at this time, it can cause the lower radiator hose to remain cold and at the same time, overheat the engine.
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2. Defective water pump
The job of the water pump is to pump coolant from the engine block to the radiator to cool the coolant.
If the water pump is not working properly, water will sit still in the engine, and water will not be pumped to the radiator.
The lower coolant hose is most likely the coolant outlet side of your engine, meaning the hose will remain cold.
3. Low coolant level
A low coolant level can create many problems in the cooling system. A low coolant level can create air pockets in the cooling system and cause the water pump to sit in an air pocket.
The coolant level is very easy to check, so open the hood and read your car’s manual to find the coolant reservoir. Remember to never open it when the engine is hot because it will boil and splatter everywhere if you do.
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4. Air in the cooling system
Air pockets in the cooling system are something you really don’t want to have there. Air pockets can create overheating and prevent circulation from working properly.
It can also create an air pocket around the water pump, preventing it from pumping water anywhere.
The air in the cooling system may come from a bad head gasket or after a coolant change. If you know you recently changed the coolant, you need to properly bleed the system.
Air in the coolant may also have been caused by a low coolant level.
5. Clogged cooling system
In rare cases, the cooling system may become clogged. However, this is not very common, as the main coolant hoses are quite large. However, if anyone has ever run their car without coolant and only water, there may be a lot of rust inside the engine.
This, combined with a leaking head gasket, can cause a lot of damage to the cooling system. Try bleeding the cooling system if you have tried everything else.
6. No problem
In many cases, when it comes to a cold lower radiator hose, there is no problem at all! The engine must be very hot and almost overheated before the thermostat will let coolant through.
If your car is not overheating, but the lower coolant hose is cold when you feel it, it could mean that it is not hot enough and therefore there is no problem with your engine. .
