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No Pressure in Radiator Hose (What Does It Mean?)

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  • 10 min read

Last Updated on: 7th September 2023, 12:47 am

No pressure in the radiator hose is often a red flag pointing to complications within the cooling system.

This could be due to a clogged or punctured coolant hose, a malfunctioning thermostat, an ineffective radiator cap, or other related concerns.

In this article, we will delve into the significance of no pressure within the radiator hose and the reasons that cause this.

What Is a Radiator Hose?

Radiator hoses constitute a crucial part of an automobile’s cooling mechanism, tasked with the movement of heated coolant to and from the engine and the radiator.

Customarily, these hoses are fabricated from robust, superior-grade rubber substances that have the resilience to endure the intense heat and pressure emanating from the engine.

With regard to design, radiator hoses are intended to have an ample diameter to facilitate the substantial quantity of coolant that is required to circulate through them.

Furthermore, they are available in a spectrum of forms and lengths to be compatible with various engine layouts.

To affix the hoses to the engine and radiator, fittings and clamps of a specialized design are employed. These ensure a steadfast and impermeable linkage.

a diagram showing a the layout of a cars cooling system

Causes of No Pressure in the Radiator Hose

In this segment, we will examine the multitude of reasons that may lead to a reduction of pressure within the radiator hose, which subsequently diminishes coolant circulation and potentially results in the engine overheating.

Let’s delve into the varied origins of this pressure reduction, and the means to identify and rectify them.

  • Coolant leak
  • Low coolant level
  • Kinked and twisted hoses
  • Clogged hoses
  • Faulty radiator cap
  • Faulty thermostat
  • Faulty water pump

1. Fissures, Cracks, and Holes in Coolant Lines

The most common causes of low pressure in the radiator hose are fissures, holes, or cracks within the coolant channels.

These can manifest as a consequence of the hose undergoing natural degradation, being subjected to repeated temperature fluctuations, or sustaining physical damage from road debris.

Consequently, the coolant fluid may leak from the radiator hose, causing a drop in the system’s pressure and raising the risk of engine overheating.

To pinpoint this issue, closely examine the coolant hoses for conspicuous indications of wear, such as fissures, perforations, or ruptures, and substitute any impaired hoses with fresh ones.

For a temporary solution, you might also consider applying a leak sealant.

examples of what damaged coolant hoses look like

2. Low Coolant Level

A secondary reason for no pressure in the radiator hose can be attributed to low coolant levels.

When there isn’t enough coolant, the water pump can’t effectively circulate it, resulting in a decrease in pressure within the radiator hose.

This scenario may arise from a leakage in the cooling system or could be a simple consequence of evaporation over a period.

To identify this issue, scrutinize the coolant level in the radiator and top it up if necessary.

It is imperative to maintain your cars coolant level within the range demarcated by the “min” and “max” markers on the reservoir.

topping up coolant level

3. Kinked and Twisted Coolant Hoses

Another factor leading to a reduction in pressure within the radiator hose is the presence of kinked or twisted coolant hoses, as these obstructions can impede the seamless flow of coolant through the system.

This may be the result of incorrect installation, vibrations from the engine, or external harm to the hose.

To tackle this issue, carry out a thorough examination of the coolant hoses for any indications of kinks or twists and rectify them by straightening any hose that is not properly aligned.

There may be instances where a hose that has remained kinked or twisted for an extended duration will need to be replaced.

kinked radiator hose circled in red

4. Clogged Radiator Hoses

Another culprit behind the decline in pressure within the radiator hose is the congestion or obstruction within the hoses, as these can hinder the circulation of coolant through the system.

Such blockages may be attributed to accumulated debris, corrosion, or other impurities inside the hose over time.

To identify this issue, examine the coolant hoses for any indications of clogging, and carry out a cooling system flush to remove any debris.

5. Faulty Radiator Cap

The radiator cap plays a pivotal role in sustaining the pressure within the cooling system, and a malfunctioning radiator cap can lead to a decrease in pressure in the radiator hose.

The malfunction could stem from a compromised seal or a breakdown of the mechanism that relieves pressure.

To pinpoint this issue, conduct a close examination of the radiator cap for any evidence of wear, tear, or leakage, and if needed, substitute it with a new one.

radiator cap circled in red

6. Faulty Thermostat

The thermostat is in charge of regulating the coolant’s circulation through the engine, and if it malfunctions, it can lead to a reduction in pressure within the radiator hose.

Such malfunctioning can arise from a failure in the temperature-detecting component or the valve that controls the flow of the coolant.

To identify this issue, examine the thermostat for any indications of wear and tear or leakage, and if required, install a new one in its place.

> See the signs of a faulty thermostat

a working vs faulty car thermostat

7. Faulty Water Pump

The water pump holds the critical role of driving the coolant through the engine, and when it’s in disrepair, this can lead to a decrease in the radiator hose pressure.

The issues in a water pump can stem from the failure of components like the bearings, impeller, or the drive belt that propels the pump.

This malfunction can consequently lead to diminished or absent coolant circulation, causing the pressure within the radiator hose to be low, and potentially resulting in the engine overheating.

To tackle this problem, carry out an inspection of the water pump for any signs of damage or leaks, and also assess the drive belt for any indications of wear or slackness.

In the event of a compromised water pump, it is advisable to replace it with a new unit.

a mechanic holding a car water pump

No Pressure and Overheating

When the radiator hose experiences a lack of pressure, it can culminate in the engine getting excessively hot.

This might occur due to improper circulation of the coolant, rendering it ineffective in dispersing the heat generated by the engine.

Such overheating can wreak havoc on the engine, leading to severe damages like the deformation and fracturing of the cylinder head, cylinder liners cracking, or even engine block damage if not dealt with swiftly.

Signs of overheating include the following.

  • A coolant temperature gauge showing higher temperatures or in the red
  • Steam from the area surrounding the engine bay
  • An alert illuminated on the dashboard or warning light

No Pressure Without Overheating

In certain scenarios, the radiator hose might lack pressure, yet the engine doesn’t overheat.

This phenomenon can occur if the coolant level is diminished, the thermostat is malfunctioning, or the water pump is not operating efficiently.

In these instances, the coolant continues to circulate, albeit not at the ideal pressure or speed. It is crucial to rectify these issues since they can escalate into more grave complications down the line.

Causes of No Pressure in the Upper Radiator Hose

There are a variety of factors contributing to the lack of pressure in the upper radiator hose.

  • Obstructed coolant hose or radiator: One of the prevalent reasons is the obstruction in the hose or radiator, which can be attributed to the accumulation of sediment or debris. This hampers the coolant flow and diminishes pressure in the coolant hoses.
  • Defective thermostat: Yet another factor could be a defective thermostat, which can impede the appropriate flow or timing of the coolant.
  • Compromised radiator cap: A further factor can be a malfunctioning radiator cap, leading to the leakage of coolant and a subsequent reduction in pressure within the engine cooling system.
an example of an upper radiator hose

Causes of No Pressure in the Bottom Radiator Hose

The lower radiator hose, often referred to as the coolant return hose, has the responsibility of transporting the coolant back to the engine once it has undergone cooling within the radiator.

A low pressure within this lower radiator hose can be attributed to several factors, including the following.

  • Defective water pump: A malfunctioning water pump can result in an absence of pressure in the bottom radiator hose.
  • Obstructed coolant hose: Blockages in the radiator or coolant hoses can impede the flow and consequently the pressure of the coolant within the engine cooling system.
  • Dysfunctional thermostat: The thermostat of a vehicle can fail to function properly, leading to decreased pressure in the bottom radiator hose.

It’s worth noting that if the engine is in its initial stages of warming up and hasn’t reached its operational temperature, the bottom radiator hose is likely to be cool and exhibit low pressure since the coolant hasn’t started circulating through it yet.

Moreover, a leakage in the radiator hoses can be another reason for the pressure deficiency and must be attended to without delay.

an example of what the lower radiator hose looks like

Why the Radiator Hose Is Soft

A pliable radiator hose serves as an alert that there may be an underlying issue with the cooling system.

This could signify that the hose has aged and warrants replacement, or there might be a complication regarding the pressure within the cooling system.

Such a situation can arise if the radiator cap is not operating as intended, failing to alleviate pressure appropriately. In both scenarios, it is vital to get the hose inspected and, if required, replaced.


An absence of pressure in the radiator hose is a critical problem that can culminate in the engine overheating and sustaining damage.

Being vigilant about the signs of this problem and addressing it without delay is essential.

The contributing factors can encompass a clogged hose, a non-operational thermostat, a malfunctioning water pump, a leak within the hose, or an ineffective radiator cap.

Keeping a close watch on the pressure within the radiator hose and proactively handling any problems can avert expensive repairs and extend the engine’s lifespan.

You can temporarily repair a coolant leak by using a leak sealant.

  • Andy Lewin

    Andy Lewin is a senior mechanic, ASE qualified master technician, and an experienced automotive engineer. He's passionate about serving the automotive community with the highest-quality and trustworthy information on all things automotive. He loves to write about car repairs, maintenance, car modifications and tuning, faults, and much more.

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