aycy

how to know if there is air bubble in the coolant??

hi all LOC member, my car also got those annoying sound near dashboard there. the sound is like VVVvvvVVvv something like air sound, it will only appear when the weather is cold especial night time, when the sound come out i try to switch off the aircond but also the same. the sound will become louder when i throttle my engine and only got sound when the car is moving. any idea what is the problem? any member here facing this problem before? thanks......