Signs of a Bad Radiator Cap & How to Replace It | Nissan Parts
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Blog - Signs of a Bad Radiator Cap


April 8, 2021

5 Signs of a Bad Radiator Cap & How to Replace Yours

It can be easy to neglect a simple car part like a car radiator cap, but doing so could lead to some pretty serious issues over the long haul! Between a potentially compromised radiator hose and an overheated engine, it's important to pay attention to the condition of your Nissan's radiator cap. Learn how to tell whether your radiator cap is bad and how to replace it.


Symptoms of a Bad Radiator Cap

Several symptoms can point to a bad radiator cap. Here's how to tell if a radiator cap is bad.

1. Coolant Leak

If you notice the coolant is leaking, it may signal that your radiator cap needs to be replaced. A coolant leak can happen around the radiator or radiator cap if the cap isn't adequately releasing pressure from the radiator. If you see that your radiator cap is damaged or worn out, it's probably time to get a new one.

2. White Streaks on Radiator

White streaks on the radiator could spell trouble with the radiator cap. The streaks indicate coolant has leaked out of the radiator. The leak may be the result of the cap failing to keep radiator pressure from escaping.

3. Overflowing Coolant Reservoir

If the coolant reservoir is overflowing, a bad radiator cap may be the culprit. When the cap is faulty, coolant can flow to the reservoir without releasing excess pressure, leading to a lack of necessary pressure in the radiator. This lack of pressure can cause the coolant tank to overflow.

4. Radiator Hose Problems

A bad radiator cap may trigger ups and downs in radiator pressure. This uneven pressure can cause radiator hoses to burst or tear.

5. Engine Overheating

A radiator cap that's not correctly maintaining pressure can lead to an overheated engine. Additionally, a bad radiator cap — one with a poor seal — can create air pockets within the cooling system, which may cause the engine to overheat.

How to Check If a Radiator Cap Is Bad

Before you check if a radiator cap is bad, be sure the cap and the engine have cooled off. It can be dangerous to remove a hot radiator cap, as the pressurized radiator coolant can reach temperatures of 245ºF to 265ºF and come spraying out when you remove the radiator cap.

A study published in 2016 found that 66% of injuries in the U.S. related to car radiators resulted from removing the cap on an overheated radiator. Fortunately, radiator caps' safety features on modern cars have reduced the number of serious injuries connected to radiators.

Once you're sure the radiator cap has cooled off, you can remove the cap and check for damage. Inspect the seals on the cap for damage, cracking, or any other signs of wear — is the seal hard or brittle, for instance.

Additionally, check inside the radiator cap to ensure other components like the valve, plunger, and spring aren't damaged or worn out. These pieces should be relatively easy to move while still having some resistance.

How to Replace Your Radiator Cap

Replacing your Nissan's radiator cap is one of the easiest and most affordable DIY projects you can do! Once you've determined that you need a new cap, get a replacement radiator cap with the same pressure rating as your old cap. To replace the cap, unscrew the old one and screw on the new one. It's that simple!

Replacing your Nissan radiator cap is a relatively simple repair that you can do from the comfort of your own driveway. If you need help, we recommend visiting an authorized Nissan service center near you. And when it comes to genuine replacement parts, Nissan Parts has everything you need — from replacement radiator caps to custom-fitted parts and accessories.


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