Why does my Car makes a loud humming sound under bonnet it kicks in when im at about 70kmhr and stays round i go faster not get louder softer as accelerate decellerate 92 Ford Laser?

Wheel bearing: A faulty or worn-out wheel bearing can produce a humming or growling sound that increases with speed. Have your wheel bearings checked by a qualified mechanic.

Transmission: If the transmission is low on fluid or has worn out gears, it can produce a humming or whining noise. Check the transmission fluid level and have the transmission inspected by a qualified mechanic if necessary.

Differential: The differential is responsible for transmitting power from the transmission to the wheels and can also produce a humming sound if it is worn out. Have the differential checked by a qualified mechanic if necessary.

Driveshaft: The driveshaft transmits power from the transmission to the differential. A damaged or unbalanced driveshaft can also produce a humming sound. Check the driveshaft for damage and have it balanced if necessary.

Vacuum Leak: A vacuum leak can cause a humming sound, especially at higher speeds. Check for any loose or disconnected vacuum hoses and replace them as needed.