W203 C200 cdi Electronic knocking just before engine start and just after stopping.

[Dichtung]

Hello Guys, W203, 200 diesel. Car drives as normal, but switching key to position 2 starts an electronic knocking sound coming from the bulkhead area which lasts for about 20 secs, whether engine is started or not.
Similarly, knocking (about every second) starts and lasts for about 30 secs on engine switch off.
Pulling fuse Nr. 30 stops the knocking, but then engine main cooling fan runs continuously.
Can anybody throw a few pointers for this problem?

 

[Petrol Pete]

By 'knocking' do you mean a clicking sound from behind the radio/HAVC area ? If it's the clicking thing that stops after a shirt while its the motors in the vent system trying to home but cant manage it because the link arm(s) have snapped . Common on older 203's.

And depending on which one has broken a complete Ba$tard to repair. Hope it's not this.

Bit like this.

How To Fix Mercedes-Benz Ticking Sound in the Dashboard Problem – MB Medic

www.mercedesmedic.com

 

[Dichtung]

By 'knocking' do you mean a clicking sound from behind the radio/HAVC area ? If it's the clicking thing that stops after a shirt while its the motors in the vent system trying to home but cant manage it because the link arm(s) have snapped . Common on older 203's.

And depending on which one has broken a complete Ba$tard to repair. Hope it's not this.

Bit like this.

How To Fix Mercedes-Benz Ticking Sound in the Dashboard Problem – MB Medic

www.mercedesmedic.com

Thanks for the reply PP, I`ve heard that `clicking ` sound on a relative`s Merc when the vent control cogs stripped; and I don`t think this noise is the same. In the radio area,- yes, but more like somebody hitting the other side of the bulkhead with a screwdriver head.
The car is off the road from today, - a few jobs to do and I`ll investigate further. I`ll keep you posted on that one.