We know that as a car driver, you have to deal with a number of problems which happen in your vehicle. To find the upper radiator hose hot and lower cold is also a common issue which you can face. If you do not have an idea about it or think it is a normal thing, you need to see this guide.
We will tell you what it means and how this condition can damage your car engine. After it, you will also learn the method of its repair which will be helpful for you in an emergency situation.
What Does Radiator Top Hose Hot Bottom Cold Mean?
If you see that the radiator hose of your car top is hot but its bottom is cold, it tells you engine coolant is not circulating through the radiator. In the case of the engine fully warming up but the lower hose still remains cold, it indicates something went wrong in the cooling system. It can be due to bad thermostat, clogged radiator, faulty water pump and air trapped in coolant hose.
Upper Radiator Hose Extremely Hot: Mostly, you will find the upper radiator hose too hot. It is due to the fact that it carries hot coolant from the running engine which has a temperature about 180°F to 210°F (82°C to 99°C). But if it is extremely hot than normal then there is a chance of poor cooling mixture circulation.
Lower Radiator Hose Cold: It means that the lower radiator hose is much cooler than the upper hose. It indicates that coolant is not flowing through the hose. If this motor is not reached at its operating temperature then it is a normal thing. You need to pay attention when the engine is overheating.
4 Signs of Hot and Cold Radiator Hose
If you drive a vehicle for a long time and the engine completely warms up, but its radiator hoses have a temperature difference. It is possible that your car cooling system is not well. In case of having this problem, you can feel these symptoms.
Engine Overheating
It is a common thing to find the upper radiator hose hot and lower cold when the thermostat is closed. It will be dangerous for your engine if this condition continues after normal operating temperature. As a result, you will see a warning light on your dashboard and temperature gauge also enter the red zone.
Poor Cabin Heat
In case of weak circulation of coolant in the motor can disturb your engine working. Because hot cooling liquid does not reach to the heater core. That's why it starts to produce cold air or change the temperature on its own. This thing produces the temperature difference between top and bottom radiator hoses.
Gurgling Noise and Smell
You can feel the sweet chemical smell which comes from under the hood. It is due to the cold fluid which becomes very hot and starts to boil. You can also notice bubbling noise from the dashboard or engine. It indicates that air is blocked in your vehicle cooling system which produces such gurgling sounds.
Leak and Steam
Sometimes, cooling agents leak due to high pressure which causes puddles under your car. You can also see vapor or steam that indicates the motor is overheating. It is all due to the coolant circulation system not working properly. As a result, you see the top radiator hose hot and bottom hose cold.
Why is my upper radiator hose hot and lower cold?
It is normal that you find the upper radiator hose hot while the lower hose is cold. It occurs in those situations when you run your car for a few minutes and the engine does not heat up completely. However, its other common reasons are as follows.
Stuck Thermostat
If you face this situation of heat difference or engine overheating, it is a strong clue that the thermostat is closed. It is basically a temperature control valve in your vehicle engine. It allows coolant to move through the radiator. But in case it's stuck, hot fluid does not enter the lower radiator hose. As a result, it remains cold.
Radiator Cap Issue
Actually, it is not only a lid of the radiator. It's a pressure valve that controls the pressure of coolant. If the cap can not hold pressure, cold liquid can boil earlier. It creates steam pockets and causes poor circulation. This heat can’t transfer fluid in a proper way which gives you unexpected results in the shape of a cold radiator hose.
See Also: Faulty Radiator Cap Symptoms: 8 Warning Signs & Solution
Air Lock
Air in the cooling system can lead to the coolant flow block. You can understand it like this if you put your thumb on the straw. Due to the presence of bubbles, water pumps struggle more to move the fluid. It makes the upper hose hot because the engine is warm. But the lower hose remains cool due to weak cold fluid movement.
Low Coolant Level
If the coolant level drops enough that the radiator can not receive the proper fluid for its working. But the engine starts to heat this small amount of cold liquid. As a result, the top hose of the radiator becomes hot. This hot fluid does not circulate to the bottom hose which keeps it cool as compared to the other hose.
Clogged Radiator
It is a common reason for poor movement of coolant through the system. Sometimes, dirt, rust and old fluid block the path of fluid flow which causes a weak supply of cold fluid to the radiator. Due to the low amount of coolant, the engine also produces extra heat which keeps the upper radiator hose too hot.
Water Pump Failure
There is no doubt that the water pump is the main part of the cooling system which circulates the coolant in the whole motor. If its impeller is damaged or loose on the shaft, it starts to move without fluid. In this condition, the top hose can get minimum heat but the bottom radiator hose remains cool which affects the engine.
Steps To Fix Changing Temperature of Top & Bottom Radiator Hoses
If you want to solve this problem with the cooling system, you have to wait for the engine to cool down. Then find the main cause of why is my top radiator hose hot and bottom cold?
1. Remove Trapped Air
As, trapped air causes poor circulation of coolant. So, you can remove it by using these tips carefully.
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First of all, you should park your car on a plain surface and make sure its front side is high.
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Then you have to open the radiator cap. Always open the hood of the car when it is cool.
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You need to place a spill free funnel in its opening and add the coolant properly.
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Now, you can start your car. Let its heater to a maximum level that it heats the engine.
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You have to run it until all the bubbles escape. You can also squeeze the hose to remove air.
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If air pockets are removed then you can turn off the vehicle. Also close the lid of the radiator.
2. Replace Thermostat
The broken thermostat can also be the cause of upper radiator hose hot and lower cold. To get rid of this trouble, you can replace the thermostat housing. For this process, you have to find it first. Mostly, it is found where both radiator hoses enter the engine.
Then you have to remove bolts and pull out the old thermostat. You need to clean gasket material from the mating surface. After doing this, you can install a new thermostat with a fresh gasket. But you must have to take care of its correct direction.
3. Flush the Radiator
You can also clean the dust from the radiator by following this method.
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First of all, you have to flow out the old and dirty fluid from the system which stops the coolant flow.
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You should fill the radiator with clean water. If you have a flush cleaner then you can use it.
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After this, run the engine of your car for almost ten minutes. Then turn off and allow it to cool.
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Now, you have to remove the dirty water. You can discharge it until the liquid comes clean.
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At the end, you must refill it with a fresh coolant which you use early. You can also add distilled water.
4. Check Water Pump
As we discussed above, without a water pump coolant can not move through the cooling system. In case of its failure, you must repair it. If you find leaks, loose bearing and a noisy whining sound from the pump, you have to pay attention to it.
You can replace the water pump if its fans are broken. They do not push fluid to the engine in a proper way. Due to this, many other problems are created in the motor. So, you have to install a new one in your vehicle for efficient function.
Conclusion
Hopefully, you will understand about the temperature difference of radiator hoses and its reasons. With its internal problems, you also need to focus on hoses. If they are damaged, we suggest you change them. For this process, RONTEIX is here for you.
We manufacture silicone radiator hoses which have extra layers of polyester that make them strong. As a result, they bear high temperature and pressure without cracking. Plus, you can also get all types of rubber hoses. To buy them at wholesale price, you can contact us anytime.
