Excess pressure can blow up hoses, the cap itself, and any other weak points in the system. Second, while some pressure is good, too much is detrimental. Without a pressurized system, the coolant will start to boil, and your engine won’t be able to cool down effectively. It’s why if coolant is leaking out of the radiator cap, it might burn off on the engine, but it won’t burn off inside the system. This pressure raises the boiling point of the coolant. Directs coolant to the radiator through a vacuum valveįor starters, your radiator cap pressurizes the system.Relives excess pressure to the reservoir.There are four functions of the radiator cap, and if any one of them isn’t working correctly, you’ll run into problems.

The radiator cap might be the most overlooked component in your vehicle’s cooling system, but it might be the most impressive. The result will be a lot of steam coming from your engine or your radiator cap as the coolant boils out of the system. But if you have a faulty radiator cap, the coolant won’t reach the right temperature, and it can start to boil. When everything is working correctly, the radiator cap does a great job at pressuring the system to raise the coolant’s boiling point. While we’ll get more into how it works later in the article, just know that a bad radiator cap can lead to an overheating engine! 6. Your radiator cap does a few different things to keep your engine at the correct temperature. How a Radiator Coolant Overflow Tank WorksĦ Causes of Oil in Coolant Reservoir & What to do 5. But if the radiator cap isn’t working correctly, it can send too much fluid back to the reservoir, sending coolant out of the overflow hose. Once the coolant reaches a specific temperature, it generates enough pressure to open up the radiator cap pressure valve, which sends the coolant back to the reservoir. It’s going somewhere! If you consistently have low coolant take a look at your radiator cap to see if that’s where it’s escaping from. If you find that you keep adding coolant, that means your engine is either burning or leaking coolant. Your vehicle has a sealed cooling system, so if you had enough coolant one day, you should have enough the next. If that happens, there will be white streaks left on the radiator where the coolant burned off. The radiator cap is at the radiator’s top, and if the leak isn’t bad enough, the coolant might burn off the radiator before it starts to drip off the bottom.

Just because coolant is leaking from your radiator cap doesn’t mean it’s making it to the ground. If your vehicle has a coolant leak, you need to investigate further, and the problem might come down to your radiator cap. Your vehicle’s cooling system is a sealed system, which means everything that goes in is supposed to stay in. The most obvious sign that something bad is going on is coolant pooling underneath your vehicle. Radiator Cap Replacement Cost Bad Radiator Cap Symptoms 1.

Coolant reservoir cap