Do you know how heat is removed from your vehicle’s engine? Basically, coolant hoses are installed in cars for this purpose. Because they transfer the generated heat out of engine and keep your vehicle at a normal working temperature. In this article, we have explained what is a coolant hose, its types, material, sizes, causes of failure & solutions.
What Are Coolant Hoses?
Coolant hoses are flexible tubes which are used to transport liquid coolant in a vehicle’s cooling system. In simple words, they create a closed path where the coolant of the engine absorbs heat energy. And then this heated coolant is transferred into the radiator where its temperature is decreased.
How Many Coolant Hoses Does a Car Have?
Generally, you find 4-5 coolant hoses in a vehicle. But some racing or modified cars can have more than 6 hoses. Common coolant hoses are listed below.
1. Upper Radiator Hoses
Upper radiator hoses are coolant hoses that are connected with the radiator. The main purpose of these hoses are to transfer hot coolant from the engine to the radiator. The upper radiator hose is easy to install and remove because it is present on the upper surface.
Upper radiator hose takes heated liquid from the thermostat housing of your car’s engine to the top of the radiator. Commonly, they have 90-degree elbows & 45 degree bends in their shape.
2. Lower Radiator Hoses
Lower radiator hose is a coolant tube which carries cooled coolant from the bottom outlet of the radiator to the inlet of the water pump. This radiator hose faces higher suction of water pump plus liquid pressure. Therefore, comparatively there are more chances of failure.
3. Heater Hoses
Heater hoses are small-bore hoses (16 to 19mm) which are placed to move a small amount of coolant inside and outside of the cabin’s heater core. Its major goal is to warm the interior of your car.
Mostly, these pipes are longer than other coolant hoses. They are not bent like radiator hoses, instead they are straight hoses so you can purchase heater hoses in different sizes.
4. Bypass Hoses
Bypass hoses are small rubber or molded tubes which are part of your vehicle’s cooling system. These pipes are placed around the engine/thermostat. Basically, they are used to circulate the coolant in the engine block and water pump. Specifically, when the thermostat is closed or the heater of the vehicle is turned off.
5. Overflow / Coolant Recovery Hoses
This type of coolant pipes connect the radiator or filler neck of your vehicle with a recovery tank or expansion tank. Their primary job is to transport extra coolant out of the radiator. Actually, in case the heat rises, engine coolant expands and builds pressure.
So, if engine liquid exceeds the labeled temperature, the cap opens and overflow hose takes coolant toward the recovery tank.
Where Are Coolant Hoses Located?
| Type of Coolant Hose | Placement in a vehicle |
| Upper radiator pipe | At top of engine |
| Lower radiator hose | At bottom of the engine |
| Heater hose | Run from the engine block or water outlet into dashboard |
| Bypass coolant pipe | Installed on or near the water pump |
| Coolant reservoir hose | Beside plastic coolant expansion or overflow tank |
Coolant Hose Material
What are coolant hoses made of? In the market EPDM rubber and high quality silicone is used to create automotive hoses.
EPDM rubber coolant hoses: EPDM (Ethylene Propylene Diene Monomer) rubber is an artificial rubber which is known for its durability and flexibility. This is why most modern vehicles use rubber coolant tubes for their vehicles. This rubber provides an outstanding temperature tolerance of more than 120°C.
Silicone coolant pipes: Silicone coolant hoses are installed in high-performance, turbocharged and heavy-duty vehicles. These coolant pipes show temperature resistance of +177°C and higher spikes. Silicone shows extra resistance to harsh chemicals that are present in coolant.
Therefore, silicone hoses are more durable and flexible. Furthermore, silicone pipes are available in vibrant colors, which are famous among car enthusiasts.
Coolant Hose Size Chart
When you buy a coolant hose you have to see its inner diameter. Because fitting and capacity flow of the coolant hose depend on its inner diameter. Outer diameter of a hose is a combination of external thickness and inner diameter.
| Nominal size (millimeter) | Nominal size (inch) | Dash size | ID in inches | OD in inches |
| 15.875 mm | 5/8″ | -10 | 0.625 | 0.945 |
| 19.05 mm | 3/4″ | -12 | 0.750 | 1.10 |
| 22.225 mm | 7/8″ | -14 | 0.875 | 1.20 |
| 25.4 mm | 1″ | -16 | 1.000 | 1.40 |
| 31.75 mm | 1-1/4″ | -20 | 1.250 | 1.60 |
| 38.1 mm | 1-1/2″ | -24 | 1.500 | 1.90 |
| 44.45 mm | 1-3/4″ | -28 | 1.750 | 2.10 |
| 50.8 mm | 2″ | -32 | 2.000 | 2.40 |
| 57.15 mm | 2-1/4″ | -36 | 2.250 | 2.60 |
| 63.5 mm | 2-1/2″ | -40 | 2.500 | 2.90 |
Causes of Coolant Hose Failure and Solution
There can be multiple reasons behind the failure of coolant hoses. In this table, I have written the main causes and their solutions as well. So, you can read it if you encounter any problem or want to protect your car from them.
| Reason Behind Failure | Solution |
| Higher pressure of cooling system | Check radiator cap and see if there is any clogged hose |
| Higher temperature (200°F) | You should protect the hoses from heat sources |
| Age related damages | Change the hose in advance before it gets expired |
| Chemical degradation | Change the coolant quickly because coolant become acidic if it fails |
| Physical damages | Be careful when you drive on a broken or under construction road |
| Oil and other petroleum products | Fix the leakage fastly even if it is external |
How Long Do Coolant Hoses Last?
The lifespan of a coolant hose depends on its type, material, quality and operating conditions. But its average life is 4 to 7 years. You can drive your car for 50,000 to 100,000 miles and then change the hose even if you do not find any damage. Always remember, durability of the coolant pipe can decrease due to heat, thermal cycling, physical stress, UV rays and ozone exposure.
How often should coolant hoses be replaced? When the hose has reached its total lifespan you must change it. Furthermore, if you notice any type of cut, scratch, swelling and pulling.
Coolant Hose Manufacturer
Coolant hose is an essential part of a car’s cooling system. So, if you want to purchase coolant hoses you should choose a reliable supplier for them. RONTEIX provides customized silicone and rubber hoses with 18 years of experience in automotive and industrial hose production.
In addition, we offer coolant hoses in different shapes, colors, materials, and sizes. If you contact us we can deliver your product very soon because our mold production requires only 3 days.
To Sum Up
Finally, we can say that you understood all the details about coolant hose & why it is important for the cooling system of your car. You must inspect all hoses before a long drive even if there is no visible damage. Our recommendation is that you can touch and squeeze them to check their internal condition.
Commonly Asked Questions
What Does a Collapsed Coolant Hose Mean?
A collapsed hose means vacuum or extreme suction is created in the cooling system of your vehicle. This condition flatten or squeeze inward instead of holding its required shape.
What Causes a Coolant Hose to Burst?
There can be multiple reasons behind the bursting of a coolant hose. For example degradation of the hose, environment damage, engine overheating, physical hitting plus internal pressure spikes.
Why Are My Coolant Hoses Hard?
Naturally, coolant pipes get firm or stiff when engines get heated. Because a normal cooling system of your car runs under a pressure of about 15PSI. Although, if they feel rock hard or remain hard even when the engine is cold down.
Are Silicone Coolant Hoses Better?
Yes, silicone coolant hoses are better than standard EPDM rubber hoses. Especially, in case of extreme pressure and temperature. Moreover, silicone hoses are more flexible and have a longer lifespan.
