Is it okay to drive with no coolant in the upper radiator hose?

Coolant in the car’s engine system plays a crucial part in keeping the vehicle operating. As a driver, you might be curious about what happens to your car’s engine if you run it without coolant or with a minuscule percentage of coolant. I’ve compiled all of the things you’ll need to know about this topic, so you won’t be an ordinary, inattentive driver anymore.

It’s dangerous to operate a vehicle with no engine coolant since it could damage some of the engine’s secondary and even primary components. It’s preferable to pull over if you’re running low on coolant. It is not a good idea to drive such a car for even a few minutes because it might cause serious engine damage and result in high repair bills.

Many modern automobile brands have a coolant cut-off feature that detects a lack of coolant and monitors the engine temperature. If the car’s cooling system is depleted of coolant, the engine temperature rises rapidly.


When you own an older vehicle, you must be aware of the indicators of coolant deficiency to avoid your engine overheating, seizing, or bursting a gasket. You can drive for a long time if your car’s coolant level is low. It all depends on the amount of coolant present.

You can drive your automobile for a few days if it’s low but above the minimum. However, if it is less than the minimum, do not even attempt to start your engine. The coolant is a solution of antifreeze and water that circulates through the radiator and engine.

Its main purpose is to keep the temperature of your engine at a safe level and prevent it from overheating. Coolant functions at higher temperatures because of its higher boiling point. Its job is to reject the heat generated by the engine and dissipate it into the atmosphere via the car’s radiator.

Why is the top radiator hose hot & the bottom is cold in my Honda?

When the coolant is circulating, this is how it should be. The heated coolant enters through the top hose, is cooled by the radiator, and then re-enters through the bottom pipe. However, if there is no circulation, the radiator could be blocked.

The thermostat is closed when the engine is warming up, and neither the top nor the bottom radiator hoses will be hot. The hot coolant will flow to the radiator after the thermostat is turned on. The upper hose will be quite hot, while the lower hose will be slightly cooler. If the bottom hose remains cold, the radiator is clogged.

Why is my car’s upper radiator hose not getting hot but the bottom is cold?

When the heater is turned on, the temperature of the in-going and outgoing heater hoses should be similar. If not, a repair may be necessary. When the upper radiator hose begins to heat up before the engine has fully warmed up,

This indicates that the thermostat is not properly closing or is open all of the time. It suggests the thermostat is blocked if it does not get hot at all. The thermostat should be replaced as soon as possible in each of these circumstances.


Putting a thermostat in a pot of water and bringing the water temperature up to the thermostat’s opening temperature is one technique to test it. On the thermostat, this is inscribed. Change the thermostat if it doesn’t open or opens 5 degrees late.

If the thermostat is set at the proper temperature, you may have a problem with the system’s circulation. This could be caused by a clogged radiator or impeller fins on a water pump. If you take the thermostat apart and test it, it should work. Then, with both hoses detached, flush the radiator with a garden hose to determine if any scale or dirt is blocking it.

Is the bottom radiator hose supposed to be hot?

The lower radiator hose must always be cooler than the upper radiator hose. The upper hose is used to deliver hot coolant from the engine to the radiator. while the bottom hose carried the engine’s cooled coolant from the radiator.

The coolant from the engine runs to the bottom of the radiator, where it is cooled and sucked back into the engine. The suction hose in the bottom radiator hose is the most important part.

The water pump draws coolant from the radiator into the engine as it rotates. This causes a low-pressure zone at the bottom of the radiator, which can cause a regular hose to collapse.

Why is my top radiator hose hot and the bottom cold?

When it comes to a cold lower radiator hose, many times there isn’t even an issue! Before the thermostat allows the coolant to pass, the engine must be extremely hot, almost to the point of overheating.

A defective thermostat, a bad water pump, or a low coolant level are the most common causes of a cold lower radiator hose. Airlocks or a clogged coolant system can also cause it.

In rare instances, the coolant system might become clogged. However, because the primary coolant pipes are so large, this is not particularly common. This, along with a failing head gasket, might result in a large amount of coolant system debris. If you’ve exhausted all other options, try flushing the cooling system.

Why is my bottom radiator hose hot?

Whenever the engine is heated and the thermostat is open, the top hose should be somewhat warmer than the bottom hose, but not by much. Otherwise, the coolant returning to the engine will be too cold.

The goal is to keep the temperature as consistent as possible. The bulb, in either case, pointed to the hottest region. If you have even the slightest suspicion that the engine is overheating, the thermostat must be replaced. The wax will get too hot and runny, seeping out and causing the thermostat to malfunction. This may be why your radiator doesn’t heat up evenly.

Why does my radiator hose have no pressure?

This side effect is not caused by a faulty hose. Whenever a radiator hose can be squeezed, the cooling system is under pressure. This, however, could indicate a problem. Cooling components are designed to withstand pressure.

The above raises the coolant’s boiling point, allowing it to operate at temperatures higher than 212 degrees Fahrenheit. These signs point to the possibility that the thermostat is stuck open.

Even before you drive for a short distance, a stuck open thermostat will allow the engine to overheat. Furthermore, pressure in the cooling system varies for a variety of reasons, and you could simply be squeezing the hose at a time when there isn’t any.

Should my upper radiator hose be hard when the engine is warm?

When your car’s engine gets heated, the radiator hose should be firm. because there is a buildup of hot water pressure inside the engine block and radiator.

The radiator cap is spring-loaded, allowing the boiling coolant to flow back into the overflow reservoir. You will be scalded if you open or touch the radiator cap when the engine is hot.

Typically, the intake is difficult to compress by hand, and the outlet is impossible. For a short time, both hoses will be inflated to roughly 25 psi. When the engine cools down, both after you turn it off and while it’s under vacuum.

When rubber ages, the molecular interlinking increases, and the elasticity decreases. This promotes cracking and webbing, and the pressures that the hose could previously withstand result in leaks, typically under the hose clamps.

How to fix radiator hot at top cold at the bottom

Step one: Find out which radiators are the source of the issue.

Is there sludge buildup in all of your radiators? Or do your radiators only operate on the first floor but not the second? The first step is to figure out which radiators are the source of the issue. Sometimes it’s just a single radiator that refuses to heat up. In other cases, a blockage in one radiator prevents the heating of all subsequent radiators.

Step two: A heating inhibitor should be added to the mix.

All central heating systems should be dosed with a central heating inhibitor to prevent sludge accumulation. Most boiler manufacturers make this a requirement for warranty coverage.

The central heating inhibitor will aid in the removal of loose rust and limescale particles from your heating system. As a result, instead of a sticky build-up on pipes and at the bottoms of radiators, you’ll receive smaller sludge particles that are much easier to filter and rinse away.

System flushing is the third step.

You’ll have the best chance of clearing sludge from your system by doing a power flush. A power flush involves injecting a mixture of water and chemicals into your heating system at high pressure using a special flushing machine.

Depending on the size of your heating system, this step can take several hours. Finally, central heating sludge should be removed from your boiler, pipes, and radiators.

Step three: Install a boiler filter and a scale reducer.

After you’ve cleared the blockage, you’ll want to keep it from forming again. You’ll need two gadgets for this. With a good scale reducer, your car will be able to catch limescale as the heating inhibitor breaks it down. You can learn more about them by clicking here. A boiler filter is used to remove any other deposits that may have formed in your heating system.

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