Is your car running hot? It could be a collapsed upper radiator hose. A common problem that can leave you stranded. The causes, however, are easy to prevent.
Learn what causes a collapsed upper radiator hose and how to check your hoses and their cost to fix.
Radiator Hose Function
Radiator hoses are used to transport engine coolant to and from the radiator. The upper hose carries hot coolant to the radiator. The lower hose returns cooled fluid back to the water pump and back into the engine. The water pump continuously circulates the coolant while the engine is running.
These hoses are made to stay flexible in temperatures from around -30 degrees to 250 degrees F. For racing applications use of high-performance hoses provides even more extreme temperatures.
Generally, hoses will have a layer of aramid, polyester, or Nomex longitudinal fibers to help the hose withstand the pressure. Hoses today can often last over 100,000 miles, with some even surviving to almost double that number!
Both upper and lower hoses may also have an internal coil spring to help reduce the possibility of hose collapse occurring.
However, a collapsed radiator hose can happen in some cases, and if not repaired, could cause severe damage to the engine. Fortunately, fixing a collapsed hose is often an inexpensive and easy repair.
What is a “Collapsed” radiator hose?
A collapsed radiator hose looks like a long, skinny flat tire. Very noticeable! One or both hoses can go flat if the cooling system sees a localized or complete vacuum (negative pressure) condition.
Why Is My Radiator Hose Collapsed?
Here are two possible reasons for a collapsed radiator hose:
- Reason 1 – A vacuum inside the coolant system is causing one or both radiator hoses to collapse. The negative pressure will develop when the engine is off, and then the normal flow of coolant returning from the expansion tank is obstructed. The vacuum problem could be due to #1 and #2 below.
- Reason 2 – If the radiator flow is restricted (a clogged radiator), this could cause the lower radiator hose to collapse. See cause #3 below.
#1. Bad Radiator Cap.
The number one most frequent cause of a collapsed radiator hose is an inoperative one-way valve in the radiator cap. This could be due to aging or contamination of the radiator cap by gunk. If you see a collapsed hose, either the top or bottom hose, follow these steps:
Never unscrew the cap when the engine is hot.
- With a cool engine, remove the radiator cap.
- If upon releasing the cap, the hose(s) quickly return to normal size, the problem is either the radiator cap or a blocked vent hose.
- Inspect the radiator cap. If it has gummy deposits, it may be possible to clean it. Use dishwashing detergent and a soft toothbrush to clean all the gunk off. Rinse the cap thoroughly. Wipe the mating surfaces of the radiator (or expansion tank) to remove any deposits with a clean shop towel.
- Replace the radiator cap.
- Start the car and warm the engine up, allowing antifreeze to flow into the expansion tank. A short drive will help this process get going. Turn the engine off, then once the engine cools, check to make sure the hose(s) are no longer collapsing.
- If the hose collapsing still occurs, a defective cap needs to be replaced. Prices at your local or online auto parts store for new caps are in the range of $8 to $25.
Are You Using Dex-Cool Antifreeze or Stop Leak?
Both the Dex-Cool and Stop Leak gunk build up in the radiator cap. If you remove the radiator cap (after letting the engine cool down) and you have a collapsed hose with the radiator cap gummed up, one or both of these products may be involved.
You can do either of the cleaning and replacing the radiator cap procedures above. With Dex-Cool or Stop Leak, the best practice is to check the radiator cap for deposits at every oil change and clean it if required.
#2. Blocked Expansion Tank Hose.
Although a blocked vent hose is a rare occurrence, if it happens, it will restrict air flow back into the expansion tank as the engine cools. This replicates the issue that occurs with a gummed-up radiator cap.
Similar to a faulty radiator cap, execute these steps:
- Remove the radiator cap after allowing the engine to cool.
- Note the collapsed hoses, they should return to a normal size.
- Check the cap, and if there are no deposits, the blockage is a vent hose.
- To check for a blocked hose, remove the vent hose from the fitting on the expansion tank. Remember to be careful, as expansion tanks are often plastic, and you don’t want to break this hose fitting.
- Measure a clean plastic drinking straw into the end of this hose (Women’s straw is better as it is stiff but reusable). Blow through this straw. Any restriction will be notable.
- Generally, the vent hose will route downward through several clamps and finish below the engine. Remove this hose from the retaining clamp and then use your garden hose to rinse out any particulate matter that could be the cause of blockage. If the blockage is persistent, a piece of stiff wire can be used to probe the hose.
- Replace the hose through the retaining clamps and replace it on the fitting at the expansion tank.
- Execute the engine warm-up/cool down process as described in section 5 of the “#1 – Faulty Radiator Cap” root cause above. If the coolant hoses do not collapse during this process, you have fixed the problem.
Important! Do not leave a faulty blocked vent hose unattended, as you may lose the engine when the coolant has no way to get to the expansion tank.
#3. Clogged Radiator (Lower Hose Collapse).
Restricted flow through the radiator may lead to a collapse of the lower radiator hose. This can be noticed while driving.
Usually, your first warning will be the engine temperature gauge rising above normal. Or, the warning indicator light indicates the engine is overheating.
When evidence of engine overheating occurs, execute the following steps to determine if the lower hose has collapsed:
- Stop the car, place the transmission in Park (automatic) or in Neutral (manual), and firmly apply the emergency brake. Allow the engine to idle.
- Open the hood and observe the lower hose. Remember to keep your hands clear of the hose area.
- If the hose appears to be normal size, ask an associate to gently increase the gas pedal pressure and gradually allow the engine to rev up. When the water pump spins increase with a restrictive flow through the radiator, the hose should collapse during the acceleration of the engine.
- If the hose collapses, you have identified a problem that must be addressed immediately.
- Allow the engine to run at idle or just above idle, but don’t rev the engine terribly fast, or the lower hose will flatten out. Ideally, temps should gradually return to a normal value.
- After the engine has cooled, you can proceed to your favorite repair shop at a normal and slow pace. If the engine overheats, you may need an emergency tow.
Checking Your Radiator Hoses
You should assess your radiator hoses every oil change. For this reason, the engine should be turned off and cool before checking. Never use your hands when the engine is running, because you risk severe injury.
Should I be able to Squeeze the Radiator Hoses? (the Squeeze Test)
Yes, with the engine off and cool, the hoses will be soft enough to squeeze. Hoses that are in good condition will be flexible under finger pressure and will not be squishy, or have a spongy feeling. Aging hoses will be hard and brittle.
Both hoses should have the same diameter and not have any bulges or cracks you can see. Any squishiness, brittleness, bulging or cracking are signs for immediate replacement.
Old hoses that show signs of age previously noted can rupture on their own. If you are examining a hot engine, even after it is turned off, and the hose fails, you risk severe burns and/or the possibility of blindness from the spraying coolant.
Should both Radiator Hoses be Hot?
After driving just five miles the upper hose will be quite hot. Since it is carrying coolant directly from the engine, it should be hot. If the radiator is doing its job, the bottom hose should be only warm to the touch and supplying cooler fluid back to the engine.
If the bottom hose is cold to the touch after the engine has warmed up, you probably have a problem.
Can a Collapsed Radiator Hose Cause Overheating?
Yes, a collapsed hose can cause overheating. If you are driving along the road and a hose flattens, it may restrict or even eliminate flow to your engine. Your instrument panel can give you elevated temperature reading and/or an overheating warning light.
You have to pull over to the side of the road, and shut off the engine as quickly as possible. Continuing to drive under an overheat condition can cause severe damage to your engine.
It is important to note that engine overheat problems can arise from several other causes instead of a collapsed hose.
What is the Function of the Radiator Cap?
The radiator cap closes your cooling system but allows the coolant to flow to and from the expansion tank (radiator coolant overflow tank).
Radiator Hose Replacement Cost
The cost for replacing both upper and lower radiator hoses at your auto repair shop can vary from $80 to over $500, depending on the make and model of your car. Costs to replace your hoses at your dealer can be somewhat more costly.