Can You Drive Without A Radiator Cap?

A vehicle’s radiator cap is designed to seal the radiator filler neck securely. This prevents contaminants from accessing the cooling system; it helps the system to build pressure, which raises the boiling point; it also ensures that coolant goes to the expansion recovery tank once coolant boils and expands as the pressure increases.

Additionally, the radiator cap ensures that coolant returns to the engine from the expansion tank once the system cools down.

Considering the vital roles the radiator cap plays, you may be worried if the component mistakenly gets missing. So, here’s the BIG question: Can you drive without a radiator cap? Let’s find out in this article.

Can You Drive Without A Radiator Cap?

Can You Drive Without A Radiator Cap?

Yes. It is possible to drive without a radiator cap, depending on the sort of driving. Under normal circumstances, the coolant will usually stay below its unpressurized boiling point. However, driving without the radiator cap in place isn’t advisable.

Sometimes, your coolant reservoir cap can fall off for various reasons; in case you were wondering, “Can the coolant cap come off by itself?” The component can fall off if it isn’t properly closed after a coolant refill.

The radiator cap can also fall off due to a blown head gasket. The blown head gasket can cause the cooling system to build internal pressure that suddenly blows off the rad cap.

You may be able to drive on city roads without the radiator cap and not experience any significant challenges. However, once you start climbing a hill without a radiator cap, there may be a little problem. As the vehicle’s position changes, the fluid could spill out of the radiator, resulting in loss of coolant.

Whatever the case may be, try as much as possible to avoid driving without a radiator cap. However, if you’re in a situation where it’s necessary that you drive, that’s fine. But ensure that the next possible solution is found.

What Happens If You Drive With Radiator Cap Off?

What happens if you drive with the radiator cap off? Driving with the radiator cap off will result in coolant pushing out of the radiator once it reaches boiling point. When this occurs, coolant loss can result in overheating, warped heads, and head gasket damage.

Remember, one of the radiator cap’s functions is to ensure that coolant goes to the expansion tank once it starts boiling. In other words, as the cooling system builds pressure, the coolant expands and travels into the expansion tank.

So, without the radiator cap, the boiling coolant will spill out from the radiator instead of entering the expansion tank. This can cause severe engine damage, as I’ve observed above.

The damages caused by the escape of boiling coolant from the radiator can be very costly to fix. Therefore, it’s important to avoid driving with your radiator cap off. Instead, I’d advise you to get a temporary radiator cap before buying a new replacement rad cap.

How Long Can You Drive Without A Radiator Cap?

How long can you drive without a coolant reservoir cap? You can drive your car with the radiator cap off without experiencing any significant issues until after 2 to 3 weeks. The coolant would have been exhausted within this period due to evaporation and spillage.

Once your vehicle’s coolant level drops or becomes exhausted, you’ll experience the following symptoms:

Some parts that are susceptible to damage due to overheating caused by low/no coolant include; the head gasket, cylinder head, water pump, cylinder and piston timing, etc. You may also experience crankshaft sensor failure, as well as connector rod warpage.

What Can I Use As A Temporary Radiator Cap?

Did you just misplace your vehicle’s radiator cap? Are you contemplating, “What can I use as a temporary radiator cap?

Do not worry; you can use a blanking cap or a washcloth/clean rag and elastic band as a temporary cap. To do this, first of all, turn off your car’s engine so it can cool down.

After that, clean the radiator filler neck and apply thread seal tape. Then, fix the blanking cap on. Make sure the blanking cap is securely installed, but do not over-tighten it. If you’re using a washcloth/clean rag, ensure it is placed properly on the radiator filler neck. Then, apply the elastic band to hold the cloth in place.

Nevertheless, remember that this is a “temporary cap.” In other words, this is a quick fix and shouldn’t be used continuously. So, once you have this on, drive straight to a nearby auto parts shop to get a new radiator cap. 

How Much Is A New Radiator Cap?

A new radiator cap costs around $10 to $30. However, the price depends on the type of radiator cap, its PSI, and the chosen brand. If you’re asking, “Are coolant caps universal?” The answer is no. You can find information about your car’s specific type of radiator cap and the pressure rating in the owner’s manual.

The information is also available on the radiator cap. But if you’ve misplaced your radiator cap and can’t find the information in your car’s manual, ask an expert auto technician or search it online.

Once you’re sure of the exact specifications for your vehicle, get a new radiator cap immediately. If you’re asking, “Where can I buy a coolant cap?” You can check out the auto parts shop near you.

How To Install A Radiator Cap On A Car

Coolant cap replacement is pretty straightforward. Once you have the recommended radiator cap for your vehicle’s radiator, simply follow this procedure.

can you drive without a radiator cap or coolant

Step 1: Turn off your engine

Firstly, always turn off your car’s engine and allow it to cool down before performing any task around that area. Installing a new radiator is also not an exception. 

Step 2: Open the hood/identify the radiator filler neck

Once you’re sure your car’s engine is cool enough to touch parts around that area, open the hood. Next, locate the radiator within the engine compartment. You’ll find the radiator directly behind your car’s grille. It has a filler neck with an opening like a bottle.

If the radiator is low on coolant, top it off with the required quantity of the correct coolant. Then, you can proceed to the next step.

Step 3: Screw on the new radiator cap

If you have a temporary cap on it, kindly take it off and install the new cap on the radiator. The same thing applies if you’re replacing your old radiator cap. First, unscrew the old radiator cap so you can install the new one. 

Once you’ve done that, screw on the new radiator cap carefully until it sits properly. However, do not over-tighten the cap on the radiator.

Step 4: Close the car’s hood

Once you’re sure everything is done, go ahead and close the car’s hood. Then, you can start your vehicle’s engine.

Final Words

The importance of the radiator cap in a vehicle cannot be overemphasized. It’s not a component you can do away with indefinitely. Instead of asking, “Can you drive without a radiator cap?” simply find out how long you have to replace the missing cap.

You may not experience any significant issues when driving without the radiator cap at first. However, the after-effects of doing so indefinitely can be extremely costly to remedy.

Apart from running low on coolant, you stand a risk of experiencing overheating. Meanwhile, overheating has been diagnosed to be one of the major causes of engine failure.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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