On/Off hum sound from the engine???

[zishan03]

When driving my car I can here a hum sound for maybe 5 seconds which is on a loop. So it hums for 5 seconds, stops, hums for 5 seconds, stops, and so on. The sound is similar to the sound you here when you turn the key two clicks in order to check the oil in the engine using the computer.

The car is 2002 CL203 with the Sequentronic gearbox.

Anyone have any ideas what it might be?


Thanks in advance

Zishan

 

[rajinder_1]

the sound maybe the secondary air injector, but that shouldnt turn on and off like that????
are you sure its not the fan?

 

[Dieselman]

Sounds liek it's either the fuel pump pressurising or the charcoal cannister purge valve.