all about hoses

Know-How Notes: All About Hoses

Git your hoses heeere, fresh rubber hoses heeere! Your vehicle is full of fluids and vapors, and the main method of moving those fluids and vapors is through hoses. You probably already knew that, but what you may not know is that nearly every one of them is designed for a singular purpose and not interchangeable with other systems. That is right; your fuel will eat right through a vacuum line or heater hose, and your transmission fluid requires a specific type of hose as well. While you may look for a hose that is cracked and brittle before replacing, the real culprit is on the inside. The pressure of the fluid flowing through the hose, mixed with contaminants, is what wears out hoses. Just because it is liquid does not mean it isn’t causing wear, one look at the Grand Canyon will disprove that notion.

Types Of Hoses

Low Pressure Fuel Hose

Low pressure fuel systems, the kind used in vehicles with carburetors, see pressures between 6 and 10 psi. Most fuel line is made of black nitrile with nylon cords between the layers for strengths. This hose is typically good for pressures up to 25 psi, beyond that you need EFI hose. Standard fuel line is capable of supporting gasoline, diesel, biodiesel, ethanol, and oil.  

<a href="https://www.napaonline.com/en/p/NBGH176?cid=social_blog_122017_hoses" target="_blank" rel="noopener">Fuel vapor hose</a> is labeled as such, if it does not say it is safe for fuel, DO NOT use it for fuel. A melted hose full of gas is a really bad day.

Fuel vapor hose is labeled as such, if it does not say it is safe for fuel, DO NOT use it for fuel. A melted hose full of gas is a really bad day.

High Pressure Fuel Hose

Designed for the higher pressures of an EFI system, typically 30-100 psi. The clamps used on these hoses need to be rounded, a standard flat worm-drive clamp can cut into the hose. Instead, use the rolled edge clamps designed for EFI applications. Of course higher pressure applications should have specialty fittings instead of hose clamps.

This is NOT for use in EFI systems, EFI hose needs to support much higher pressures than standard fuel vapor hose.

This is NOT for use in EFI systems, EFI hose needs to support much higher pressures than standard fuel vapor hose.

Coolant Hose

Coolant hoses come in two flavors – heater hose and radiator hose. They hoses are made the same, but the sizes are real difference. Heater hose is generally ½, 5/8, and ¾-inch in diameter. There are different types of heater hose, from standard to heavy duty. The heavy duty hoses have extra protection from exterior abrasion and damage. All heater hoses are lined with nylon cords for durability. Coolant hose is not safe for fuel.

Coolant hoses can be formed or loose spooled. The most common sizes of heater hose are 5/8" and 3/4".

Coolant hoses can be formed or loose spooled. The most common sizes of heater hose are 5/8″ and 3/4″.

 

Inside a heater hose you can see the edges of the cords. Note the thin wall and sparse cord, this is low-pressure stuff.

Inside a heater hose you can see the edges of the cords. Note the thin wall and sparse cord, this is low-pressure stuff.

Radiator hoses are also lined with cords, but they are molded to shape. These hoses can be anywhere from 1-inch up to 3 inches in diameter, and are designed to resist collapsing. Some radiator hoses have large springs inside them to ensure they do not collapse. A radiator hose can collapse as the hot coolant cools, creating a vacuum.

Radiator hoses is much larger in diameter and even thinner that heater hose. Often, these hoses will have a coiled spring inside to keep them from collapsing as the temperature changes.

Radiator hoses is much larger in diameter and even thinner that heater hose. Often, these hoses will have a coiled spring inside to keep them from collapsing as the temperature changes.

Hydraulic Hose

There are several hydraulic systems in most cars, namely power steering and brakes. Both require high-pressure hoses that can handle 2,000psi or more. These hoses are user-replaceable, but unless you have special equipment, you can’t just make your own. These hoses have special compressed fittings that secure to the hose to hold the high pressures. These hoses are lined with braided steel between the layers. This makes the hose very stiff and hard to flex or bend.

Hydraulic hose must hold thousands of pounds of pressure, and requires special fittings to support it.

Hydraulic hose must hold thousands of pounds of pressure, and requires special fittings to support it.

 

Inside a rubber hydraulic line is braided steel to support the pressure of the fluid. This makes the hose very stiff and hard to bend.

Inside a rubber hydraulic line is braided steel to support the pressure of the fluid. This makes the hose very stiff and hard to bend.

 

The alternative to the thick rubber hose is a stainless steel line, which uses a teflon core tube encased in braided stainless steel. These are more costly, but they last forever.

The alternative to the thick rubber hose is a stainless steel line, which uses a teflon core tube encased in braided stainless steel. These are more costly, but they last forever.

The one exception is the power steering return line hose, which is not under much pressure. These can be cut and secured with standard hose clamps. Your automatic transmission is also a hydraulic system, and the fluid has to be cooled. This is done through hard lines that connect to the radiator. There is a rubber line that serves as a flex joint, this must be hydraulic hose. Most modern cars have specialty lines that are vehicle specific, but many older cars just use a length of rubber hydraulic line. This is fairly low pressure line.

A/C Hose

Your vehicle’s air conditioning system requires high-pressure hoses to contain the refrigerant inside the system. This is similar to the high-pressure hydraulic hoses, but instead of the braided steel layer, these hoses have a braided nylon for strength and flexibility. Similar to the hydraulic hoses, A/C hoses requires special equipment to attach the fittings.

Most A/C lines used today are barrier style, which can be used for all refrigerant types.

Most A/C lines used today are barrier style, which can be used for all refrigerant types.

There are two types of A/C hose – barrier and non-barrier. This is for the two main types of A/C refrigerant. The modern R134a type has smaller molecules than the older R12. If you put R134a in R12 non-barrier hose, the gas will slowly seep through the hose itself because the molecules are so small. R12 molecules are bigger than the molecules of the hose, so it does not seep out. R134a requires a barrier-type hose, which uses a plastic liner that contains the refrigerant.

The cross-section of an A/C hose shows just how thick the hose is. This hose is 13/32" on the inside, but nearly a full inch on the outside. Also note the tighter weave on the nylon cords compared to the heater hose.

The cross-section of an A/C hose shows just how thick the hose is. This hose is 13/32″ on the inside, but nearly a full inch on the outside. Also note the tighter weave on the nylon cords compared to the heater hose.

Vacuum Hose

Even modern cars still use vacuum lines, albeit less than older vehicles. Vacuum line can be rubber, PVC, or silicone. Vacuum hose is capable of handling 25psi, and is designed for vacuum, windshield washers, and radiator overflow use.

Vacuum line is just rubber, no cords. It is good for basic non-volatile fluid transfer and air.

Vacuum line is just rubber, no cords. It is good for basic non-volatile fluid transfer and air.

 

For high-pressure air, this DOT air line is the ticket. This is used for air brakes and air ride.

For high-pressure air, this DOT air line is the ticket. This is used for air brakes and air ride.

Checking Your Hoses

Hoses are wear times and they have to be checked and replaced periodically. Some hoses should just be outright replaced on a regular basis, as they are hard to check, but others are easy to determine if they are wearing out. Fuel lines should be replaced every five years. Sure, your car may be 30 years old and you have never replaced a line, but that is not a good thing. The fuel itself eats at the hose, even though it is fuel line. This leads to small pieces falling into the fuel and gets trapped in the filter or in the carburetor or EFI system. Eventually, the hose will split.

Coolant lines are easy to test. With the engine cool, grab the hose and give it a squeeze. It should resist your grip but eventually give. If it is soft, change it as soon as possible as it is thin and could rupture at any point. Any hose that has cracks, weathering, or scrapes should be replaced. Frayed cords on the cut end of the hose are not an issue, but if you see cord anywhere else, it needs to be replaced immediately. Oily hoses, especially near a compressed fitting, should be checked carefully, as that could be a sign of weeping through the hose on high-pressure applications. Bulging hoses should also be replaced, as this is a sign of weakened interior walls. Replacing a hose is fairly simple, in most cases, you will lose some fluids which are simply replaced. Some applications, specifically brake hoses, require bleeding of the system. Replacing a power steering or transmission hose means that you should flush the system before refilling with new fluid to evacuate any contaminates from the equipment itself.

Check out all the belts and hoses available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on hoses, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

about author

Jefferson Bryant

A life-long gearhead, Jefferson Bryant spends more time in the shop than anywhere else. His career began in the car audio industry as a shop manager, eventually working his way into a position at Rockford Fosgate as a product designer. In 2003, he began writing tech articles for magazines, and has been working as an automotive journalist ever since. His work has been featured in Car Craft, Hot Rod, Rod & Custom, Truckin’, Mopar Muscle, and many more. Jefferson has also written 4 books and produced countless videos. Jefferson operates Red Dirt Rodz, his personal garage studio, where all of his magazine articles and tech videos are produced.

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