No Pressure in Radiator Hose – What Are Causes and Fixes?

No pressure in radiator hose is dangerous for your engine as it can result in overheating, damage to the hose itself and low coolant levels. If they’re not quickly fixed, these symptoms can damage the engine in a short time; that is why it’s important to know what causes the problem and how to fix it. 

No Pressure in Radiator Hose

Fortunately, this article will discuss the common sources of pressure loss in radiator hoses and practical solutions to them. We’ll also answer a few pertinent questions about the hoses.

What Causes No Pressure in the Radiator Hose?

The causes of no pressure in the radiator hose include a faulty thermostat, low coolant level, air bubbles in the cooling system and a damaged water pump. Other causes include a blocked radiator, a corroded hose and electrochemical degradation. A failing hose cap can also lead to pressure loss.

A Faulty Thermostat Preventing Coolant Flow

The thermostat is located between the engine and the coolant, and its job is to allow the coolant to flow when the engine is getting hot. It has a small cylinder filled with wax on the engine side of the device. This wax melts at 180 degrees Fahrenheit, expands and pushes a rod out of the cylinder to open the thermostat. When the thermostat opens, it allows the coolant to flow through the engine and absorb the engine’s heat.

If the thermostat develops a fault, it won’t open to allow the coolant to travel through the engine. Thus, there the heat will continue to build up in the engine and cause overheating. Usually, the thermostat has to shut after the wax hardens up, ceasing the coolant’s flow. However, it can get stuck when it opens, allowing a perpetual coolant flow.

When this happens, the engine won’t reach optimum temperature, affecting its operations. Running a cold engine is extremely dangerous for the vehicle. One way to note a failing thermostat is by observing the needle on the temperature gauge. If it doesn’t reach its normal position after the engine gets hot, the thermostat is faulty.

Low Level of Coolant in the Cooling System

The main reason why the coolant pressure drops is a leak in the coolant system. If the coolant is low, the liquid volume in the radiator hose will also be low, causing no pressure in the hose. Thus, the coolant won’t be able to flow through the hoses to and from the engine, leading to overheating. The coolant has to be at the right quantity/level to cool the engine and keep it running at the right temperature. 

Causes No Pressure in the Radiator Hose

You can measure the level of coolant by simply looking through the reservoir, a see-through white container that allows you to see the coolant’s color. On the reservoir are two markings indicating the maximum and minimum levels. However, you’ll need to slightly shake the reservoir to get an accurate coolant reading.

Air Bubbles in the Cooling System

Air bubbles or air pockets in the coolant system can obstruct the flow of the antifreeze, leading to a no pressure in cooling system no leaks situation. Air bubbles form in the coolant system in different ways, and one of them is through the radiator cap. If the cap isn’t closed tightly, air can enter the system and form bubbles.

Another way air gets into the coolant is through leaks in the radiator hoses. These leaks not only allow the coolant to flow out but also give way for air to enter the system. If the hoses are leaking, it is a sign your engine is overheating. Thus, you need to call a mechanic to salvage the situation before it gets out of hand.

A Damaged Water Pump Allowing Air Into the System

Air can also enter the coolant system through the water pump, which is responsible for circulating the antifreeze. A faulty water pump will have small spaces where air can seep into the system to form bubbles. The major reason why a water pump will malfunction is the age and wear of its motor. 

Like other motor parts, the water pump eventually becomes weak and needs to be replaced. Symptoms of a bad water pump include grime around the device, a whining noise and engine overheating. Fortunately, you can replace the damaged pump yourself, which costs lesser than going to the auto shop.

Electrochemical Degradation in the Radiator Hose

Electrochemical degradation is when cracks develop inside the radiator hose as a result of a chemical reaction. This chemical reaction occurs between the coolant, radiator hose and engine fittings, which form a galvanic cell. The reaction releases electrical charges that cause cracks in the hose and result in leakages. The leakages allow the coolant to escape, reducing the pressure in the radiator hose.

To check for electrochemical degradation, do the radiator hose squeeze test. Press the ends of the hose where the degradation is more likely to take place. If the ends are squashier than the middle, then they are degrading. Another sign of degradation is the upper radiator hose soft when hot.

The solution to electrochemical degradation is replacing the old hose with a new one, ensuring the replacement has properties that can withstand electrochemical degradation.

How To Fix No Pressure in Radiator Hose

To fix no pressure in radiator hose, check the thermostat, hose and water pump to determine if they are damaged and replace them. However, clearing air pockets in the radiator involves squeezing the trapped air out while flushing a clogged radiator will make it work again.

Fixing a Failed Thermostat

Replacing a failed thermostat can be difficult, depending on its location, and may require flushing the radiator. First, locate the coolant reservoir, which is usually on the top right corner of your car’s engine. Place a bucket and remove about 50% of the fluid before proceeding to avoid spilling some. Remove the thermostat from the engine and take care you don’t damage any of its fragile parts.

Next, check the new thermostat number to ensure it matches that of the old one. Also, check the installing surfaces to ensure there’s no dirt or grime to disturb the seal. If there’s any dirt or grime, clean it with a sharp blade and then mount the thermostat. Ensure the air bleed hole is in the right position, then fix the right gasket type for your vehicle. 

Finally, fix the thermostat housing on the device and top up the coolant. Turn on the engine to allow the coolant to run through the system and eliminate any trapped air. Check the temperature gauge to see if the antifreeze temperature is within the right range.

How To Fix a Leak in the Engine Cooling System

A Low coolant volume can only be caused by leaks in the system. Thus, simply topping up the coolant won’t solve the problem, as it’ll simply leak out, causing a dangerous cycle. However, locating where the leak is can be difficult and frustrating, even for mechanics. One way to detect the position of the leak is by placing a large piece of cardboard underneath the vehicle and leaving it overnight.

Fix No Pressure in Radiator Hose

Remove any skid plate under your vehicle so it doesn’t collect the liquid. Once you see the coolant on the cardboard, you can trace the leak from there. Depending on the location of the leak, you’ll have to tighten the clamps or replace an old hose with a new one. However, if the source of the leak is the radiator or water pump, you’re in big trouble.

Replacing the radiator and water pump should be done by an expert and it’s quite expensive due to the difficulty in accessing both components. We’ll recommend you flush the radiator to help alleviate the situation.

How To Get Rid of Pockets of Air in a Coolant System

First, remove the caps from the radiator and the pressurized coolant reservoir and top up the coolant till it’s full. Turn on the engine and allow it to run for a few minutes as the coolant travels around the system, getting rid of the air bubbles. Keep adding more coolant and repeating these steps when you see air trapped inside the system. Also, you can hold the upper radiator hose and gently squeeze it to force the air bubbles out of the system.

Observe the coolant until you see no air bubbles in it, then turn off the engine and replace the radiator and the pressurized coolant reservoir caps. Observe the level of the coolant and top up if necessary.

How To Flush a Blocked Radiator

Crawl under the vehicle and locate a large rubber connected to the radiator and place your drain pan under it. Open the valve and allow the coolant to run out into the pan for about 15 minutes. Close the valve, get out from under the vehicle and move to the hood. Locate the radiator cap, remove it and pour distilled water into the radiator till it hits the “full” mark.

Turn on the engine for the water to run through the coolant system, getting rid of all debris and traces of antifreeze in the system. Turn off the engine and drain out the distilled water by removing the valve cap underneath the vehicle. Next, open the radiator cover and pour a blend of 50/50 antifreeze and distilled water into it (contact your car manual for the right mixture).

Pour the blend until it reaches the “full” mark and observe the overflow tank, a plastic container connected to the radiator. Now, turn on the engine and allow it to run for about 5 minutes while observing the coolant. Check for leaks, and if there are none, your vehicle is good to go.

Engine Cooling System

Can a Constantly Running Radiator Fan Cause a Loss of Pressure in the Radiator Hose?

A cars radiator fan constantly running can potentially lead to a loss of pressure in the radiator hose. This occurs due to the continuous cooling of the radiator, which prevents the pressure build-up necessary for proper coolant circulation. It is essential to diagnose and address the issue promptly to prevent overheating and potential car engine damage.


So far, we’ve discussed what causes no pressure in coolant reservoir/radiator hose and have demonstrated ways you can solve the problem.

Here’s a recap of all that we’ve mentioned in this article:

  • When there’s a leak in the cooling system, the radiator is blocked or the water pump is malfunctioning, the coolant won’t flow properly.
  • A faulty thermostat, low coolant volume, electrochemical degradation and air bubbles in the cooling system can also cause no pressure in the radiator hose.
  • To solve the problem, you must replace all faulty parts and flush the radiator to get rid of air bubbles in the cooling system.

Remember to mix the coolant and the distilled water according to the specifications in your car manual. Mixing it wrongly might cause no pressure in radiator hose and overheating or damage the system.

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