How to Tell If Your Vehicle's Radiator Is Leaking

How to Tell If Your Vehicle's Radiator Is Leaking

16th Oct 2019

black and white picture of classic car

Vehicle Radiator Leak

A leaking radiator is a serious problem that, when left unchecked, can lead to the death of your vehicle's engine. Consisting of dozens of narrow and vertical passages, it works in conjunction with a motorized fan to remove heat from the coolant. If your radiator springs a leak, however, coolant will escape, thereby lowering its effectiveness at controlling engine temperatures. So, how do you know if your vehicle's radiator is leaking exactly?

Look for Puddles

Conventional wisdom should lead you to believe that a leaking radiator will leave puddles of coolant underneath your vehicle. When you pull out of your driveway, look on the ground to see if there's any coolant present. Assuming your radiator is working as intended -- and isn't leaking -- there shouldn't be any coolant on the ground.

Rising Engine Temperatures

Another sign of a leaking radiator is rising engine temperatures. This doesn't necessarily mean that the temperature gauge should always be at the "cold" mark. It's completely normal for the gauge rise to about the halfway mark. With that said, for most vehicles, the temperature gauge should extend above the halfway mark. If it's at the "hot" mark -- or anywhere above the halfway mark for that matter -- it indicates your vehicle's engine is overheating, which could be the result of a leaking radiator.

Low or No Cabin Heat

You might be surprised to learn that a leaking radiator can affect your vehicle's cabin heat. To produce cabin heat, vehicles blow a fan over a miniature radiator known as a heater core. The heater core, however, is part of your vehicle's overall cooling system, so it's connected to the radiator. If your radiator is leaking, less coolant will pass through it and the heater core. And with less coolant in the heater core, you may experience low or no cabin heat during the winter.

Loss of Coolant Pressure

If your vehicle's radiator is leaking, it won't be able to hold pressure. Automotive radiators are designed to operate under pressure. As the coolant picks up heat from the engine, it expands and pressurizes. If there's a leak in the radiator, though, the coolant won't be able to pressurize. Rather, it will escape through the hole or puncture in the radiator.

You can see if your radiator is holding pressure by pressure-testing it. This involves connecting a special testing cap to the filler neck, after which you can fill it with air to the pounds per square (PSI) of pressure as specified on the radiator cap. Assuming it's not leaking, the pressure shouldn't drop.