Abnormally high temps are the classic sign a radiator is failing. if your temperature gauge on your dashboard is touching the yellow or red portion of the dial, your vehicle is too hot. On newer cars, you’ll see a little thermost… if the temperature dial randomly moves, it’s a bad sign. the temperature dial in your vehicle rarely fails on its own, so it’s concerning if the dial moves up and down erratically. Look at it while you’re driving.