How to Tell When the Rad Cap Is Leaking: 6 Symptoms

Leaks are normal occurrences in any vehicle, but that doesn’t mean they’re inconsequential. A leaking radiator cap, for example, could lead to internal damage and a heftier price to repair. To prevent that, you must keep an eye out for the symptoms of a faulty radiator cap.

Symptoms of a Leaking Radiator Cap

Be on the lookout for these telltale signs that the radiator cap is leaking:

Leaking Coolant

Coolant leaks are the most common sign of a leaking radiator cap. The cap controls the coolant’s pressure in the radiator.

Leaks could occur when the cap holds more pressure than it’s designed for or if it fails to allow excess pressure into the reservoir when the system reaches the target pressure.

The leak doesn’t always happen at the radiator cap. The coolant could escape from the gaskets, hoses, water pump, or even the radiator itself, depending on the pressure.

Overflowing Coolant

Overflowing coolant occurs when the coolant goes to the reservoir without the excess pressure, causing the fluid to overflow into the tank or release prematurely. It may occur when there’s a weak spring in the radiator cap.

Low Coolant Level

Leaking and overflowing coolant often result in low coolant levels, which could cause engine overheating or a blown head gasket. Both problems could lead to irreversible damage to the car.

If the coolant level is getting too low, you can mix distilled water into the fluid as a temporary fix. However, you shouldn’t rely on a coolant and water mix for long periods. As much as possible, always replenish the reservoir with coolant.

Overheating Engine

A leaking radiator cap often results in an overheating engine, as low coolant levels mean the fluid won’t be efficient in reducing temperatures. If left unresolved, an overheating engine could lead to engine failure, which in turn leads to bigger problems.

Steam from the Engine

The heat from an overheating engine could boil the coolant, causing it to evaporate and turn into steam. The gas could escape through a bad seal or a damaged radiator cap.

Common Causes of a Leaking Radiator Cap

The best way to prevent radiator cap leaks is to stop or prevent the factors that cause them. Here are the common culprits:

Lack of Maintenance

Poor maintenance affects the radiator cap like other components of your vehicle. It could damage the cap or aggravate any issues the part might have.

Is a busy schedule or a tight budget preventing you from taking your ride to an auto repair shop for proper maintenance? Why not do it yourself? Include a radiator cap inspection in your maintenance routine or have it replaced if you have doubts. Check for leaks or overflowing coolant as well.

However, it’s still better to let a licensed mechanic do the maintenance. Doing so prolongs the lifespan of your vehicle and could even save you money in the long run.

Wear and Tear

Wear and tear on the radiator cap is unavoidable as your ride racks up mileage. So just keep an eye out for the symptoms of an aged cap, like rust, a loose fit, and cracks.

As mentioned above, it’s best to check your vehicle at least once a year to prevent wear and tear. Generally, the radiator cap should last as long as the vehicle’s lifespan.

When you pull the radiator cap off, you should see a spring sticking down. On some vehicles, the cap fails and the spring falls out.

Damaged Radiator Hose

Internal pressure that warps or tears the radiator hoses result in a vacuum effect that leads to a damaged or leaking radiator cap.

Similarly, the situation also occurs vice versa. Meaning, an already damaged radiator hose tends to rupture the hoses.

How Do I Stop My Radiator Cap From Leaking?

Leaks from the radiator are often due to damaged or loose caps. In this case, you can stop the leak by replacing the cap.

Can I Drive With a Leaking Radiator Cap?

It’s not advisable to drive with a leaking radiator cap, even when your vehicle still runs. Sooner or later, you’re bound to run out of coolant, resulting in a blown head gasket, irreparable engine damage, or overheating.

You should take your vehicle to a nearby auto shop if you notice the first sign of a damaged or leaking rad cap.

How Much Does It Cost to Fix the Radiator Cap?

Fixing the radiator cap can set you back $10 to $35. The price could vary, depending on the auto shop’s labor fee and how much the replacement piece costs.

How Often Should You Replace the Radiator Cap?

You don’t have to replace the radiator cap often. Experts recommend replacing it every five years to prevent issues from popping up.

Some mechanics also advise replacing it every 100,000 miles, as it’s accumulated damage from wear and tear by then.

How Long Will a Leaking Radiator Last?

While it’s tempting to drive a leaking radiator to save money, it’s best to replace it immediately at the first sign of leaks. Continuing to drive with a leaking radiator can damage your engine.

While it’s tempting to drive a leaking radiator to save money, it’s best to replace it immediately at the first sign of leaks.

–Anthony Harlin, ASE Certified Master Automobile Technician

How Tight Should a Radiator Cap Be?

The radiator cap should be hand-tight. Anything more could result in damage, and anything less would be too loose, resulting in leaks.

How to Get Your Hands on a New Radiator Cap

Coolant leaks due to a bad radiator cap can cause the engine to overheat and become vulnerable to irreparable damage. On the bright side, finding a replacement is easy with the help of CarParts.com.

All our radiator caps come with a lifetime replacement and low-price guarantee, so you never have to worry about going over budget for your repair needs. On top of that, we only offer parts that pass the highest quality control standards.

Find the perfect replacement by entering your ride’s specifications into our vehicle selector to narrow the catalog to compatible caps. Then, use our search filter to filter the results based on your preferred brand, price, material, color, and more.

Expect fast and reliable shipping, thanks to our strategically located warehouses. If you have any questions, don’t hesitate to contact our round-the-clock customer service team via our toll-free hotline.

Don’t put up with the hassles caused by a bad radiator cap. Shop for a replacement radiator cap today!