3 Reasons Why Radiator Hose Collapses
Is your car’s engine running hot? Your top radiator hose may be broken. This common problem can leave you powerless, but the causes are easily avoidable. Learn what causes a top radiator hose to collapse, how to inspect the hose, and how much it might cost to repair.
What Radiator Hoses Do
Radiator hoses carry engine coolant to and from the radiator. The top hose carries hot coolant from the engine to the radiator. The bottom hose returns cooled fluid to the water pump and then back to the engine. The water pump continuously circulates this coolant while the engine is running.
These hoses are designed to remain flexible in temperatures ranging from approximately -30 to 250°F. For racing applications, high-performance hoses can offer even better heat resistance. Hose construction typically consists of layers of aramid, polyester, or Nomex fibers to help the hose withstand pressure. Hoses on today’s cars can last well over 100,000 miles, and in some cases twice as long.
Both the upper and lower hoses may contain internal coil springs to minimize the risk of the hose collapsing. However, radiator hose failure can occur under certain conditions and can cause serious damage to your engine if left untreated. Fortunately, repairs are usually cheap and easy.
What is a “crushed” radiator hose? A crushed radiator hose looks like an elongated flat tire. It is very noticeable. If there is a localized or complete vacuum (negative pressure) in the cooling system, one or both hoses may puncture.
Why did my radiator hose snap? There are two possible reasons why a radiator hose may collapse:
Reason 1 – A vacuum in the cooling system can cause one or both of the radiator hoses to collapse. This negative pressure occurs when the engine is shut off and the normal return flow of coolant from the expansion tank is cut off. This vacuum problem can be caused by reasons 1 and 2 below:
Reason 2 – Restricted flow through the radiator (clogged radiator) can cause the lower radiator hose to collapse.
1) Faulty radiator cap
The first and most common cause of a collapsed radiator hose is a failed check valve in the radiator cap. This can happen due to aging or if the radiator cap is dirty with sediment. If you notice that the top and/or bottom of the hose is crushed, follow these steps:
DANGER
Never remove the cap when the engine is hot.
1. Remove the radiator cap when the engine is cold.
2. If the hose immediately returns to normal size after you remove the cap, the problem is with a clogged radiator cap or breather hose.
3. Inspect the lid. If it’s covered in rubbery buildup, it may be possible to clean it. Use dish soap and a soft toothbrush to remove any debris. Rinse the lid thoroughly. Use a clean shop towel to wipe any debris from the radiator (or expansion tank) contact surfaces.
4. Reinstall the cap.
5. Start the car, warm up the engine, and let it run until the antifreeze flows into the expansion tank. A short drive can speed up this process. Shut off the engine and, once it has cooled, check that the hoses are not crushed.
6. If the hose still collapses, you may need to replace the faulty cover. A new cover will cost between $8 and $25 at your local auto parts store or online.
Are you using Dex-Cool antifreeze or Stop Leak?
Both Dex-Cool and Stop Leak tend to build up in the radiator cap mechanism. If you have a collapsed hose, or one that is stuck when you remove the radiator cap (engine is cold), one or both of these products could be the culprit. Follow the cleaning instructions above or replace the lid.
If you use Dex-Cool or Stop Leak, we recommend checking the radiator cap for deposits after every oil change and cleaning it if necessary.
2) Clogged Expansion Tank Hose
Clogged breather hoses are relatively rare, but if they do become clogged, they can prevent air from backing up into the expansion tank while the engine is cold. This is similar to the problem caused by a stuck radiator cap.
As with a bad radiator cap, follow these steps:
1. After the engine has cooled, remove the radiator cap.
2. Inspect the crushed hose. It should return to normal size.
3. Inspect the cap. If there is no debris, the problem is most likely a clogged vent hose.
4. To check if the hose is clogged, unscrew the vent hose from the expansion tank fitting. Expansion tanks are generally made of plastic, be careful when doing this to avoid damaging this hose fitting.
5. Insert a clean plastic straw into the end of this tube. (A hard, reusable plastic children’s straw works best.) Blow into the straw. Any restrictions will be clearly indicated.
6. Typically the breather hose is led down through several clamps and ends under the engine. Remove this hose from the retaining clip and use a garden hose to thoroughly flush out any particles that may be causing a clog. If the clog persists, a stiff wire may be useful to inspect the hose.
7. Re-thread the hose through the retaining clip and reconnect it to the fitting on the expansion tank. 8. Perform step 5 of cause “No.” above. 1 – Defective Radiator Cap (described in Engine Warm-Up/Cool-Down Process).
3) Clogged Radiator (Lower Hose Collapse)
Restricted flow through the radiator can result in the collapse of the lower radiator hose. This condition would be noticed while driving. Your first warning will be a rising temperature beyond normal on your engine temperature gauge. Alternatively, a warning light indicating overheating may come on.
When symptoms of engine overheating occur, follow these steps to assess the possibility of a collapsed lower hose:
1. Stop the car, place the transmission in Park (automatic transmission) or
Neutral (manual transmission) and firmly set the emergency brake. Allow the engine to idle.
2. Open the hood and observe the lower hose. Be careful to keep your hands out of that area.
3. If the hose appears to be normal in size, have an associate gently press the gas pedal to gradually increase the engine speed. As the water pump speed increases with restricted flow through the radiator, the hose collapses on acceleration.
4. If the hose collapses, you’ve discovered a problem that will need immediate attention. Follow these next steps:
5. Allow the engine to continue to run at idle or slightly above idle but not fast enough to flatten the lower hose. Engine temperature should gradually return to normal.
6. Once it has cooled, proceed slowly to your favorite repair shop for corrective action. If overheating reoccurs, you may have to call for a tow.
Checking Your Radiator Hoses
At every oil change, you should evaluate the condition of your radiator hoses. Never use your hands to check the hoses with the engine running as this poses risk of severe injury.
Should I be Able to Squeeze the Radiator Hoses? (the Squeeze Test)
Yes, with the engine off and cooled down, the hoses should be soft enough to squeeze. Hoses in good condition should be flexible to finger pressure but not squishy or spongy feeling. Aging hoses will be hard and brittle.
Both hoses should be of uniform diameter with no noticeable bulges or cracks. Squishy, brittle, bulging or cracked hoses are candidates for immediate replacement.
Warning
Old hoses displaying the age symptoms noted above can spontaneously rupture.
Should Both Radiator Hoses be Hot?
After a drive of as little as five miles, the upper hose will be quite hot as it will be carrying coolant directly from the engine. If the radiator is doing its job, the bottom hose will be warm to the touch as it’s conveying cooler fluid back to the engine. But if the lower hose is cold to the touch after the engine has warmed up, you likely have a problem.
Can a Collapsed Radiator Hose Cause Overheating?
Yes, a collapsed hose can cause overheating. If you are driving when a hose goes flat, coolant flow will be restricted. Your instrument panel will give you an elevated temperature indication and/or an overheating warning light.
You must pull to the side of the road and shut off the engine as quickly as possible. Continuing to drive with an overheated condition can cause severe engine damage. It’s worth noting that engine overheating problems may derive from several other causes besides a collapsed hose.
What is the Function of the Radiator Cap?
The radiator cap closes your cooling system but enables coolant to flow to and from the expansion tank (radiator coolant overflow tank).
