Ticking C Class

[Taxing Ken]

I have had my 'C' Class Coupe 220 Cdi (54 plate) now for 12 trouble free months. It is a relaxing car to drive and I am very happy with it.

My only issue is with a 'gentle' ticking noise which seems to be coming from behind the dashboard (a bit like the noise the old mechanical speedo cables sometimes made - I assume MB speedos are now electronic even though with an analog dial).

It can only be heard a low speeds say 35mph or below when tyre / wind noise does not cover it. Also it doesn't appear to change with rises / falls in speed.

Anyone got any ideas??

Taxing Ken

 

[Myros]

could be

the temperature sensor mini fan up in the light fitting, or the duovalve resonating through the pipework for the heater.
What's the approx frequency?

 

[C220GJS]

I agree with Myros re. the heater duovalve , lift the bonnet and in front of the brake master cylinder you will see a twin solenoid valve which should be clicking every second or so , the frequency will vary depending on how the heater control is set.
Geo.

 

[OmniCognateNeutronRangler]

My C240 makes a slight ticking noise too, sounds almost like tappett rattle, but only very slight. I read somewhere else on this forum that there is a valve of some kind that can often be heard opening and closing that gives this affect. Sorry, not very technical I'm afriad.

 

[C220GJS]

The duovalve !!! .http://mbclub.co.uk/forums/showthread.php?t=26888. Just to show where it is .

 

[OmniCognateNeutronRangler]

ah, yes. I suppose I should have paid attention to what I was reading. My bad.

Can you explain more abou tthe heater settings thing. i.e. can I make it stop ticking by adjusting the heater settings?

 

[C220GJS]

The default setting on these valves is fully open ,so if you are prepared to keep the heating on full all the time the ticking should stop, but that's a bit extreme don't you think. That is if the noise is coming from the duovalve.
Geo.

 

[Taxing Ken]

Thanks for the suggestions.

The frequency of the ticking noise I have is about 3 -4 per second. I'm not sure this equates to the Duovalve. Incidentally on my car (W203 220cdi) it is not situated in front of the brake master cylinder - while I know what I'm looking for I've been unable to locate it. Anyone have any ideas.

Taxing Ken

 

[Myros]

3-4hz doesn't sound like the duovalve

more likely related to the camshaft or fuel system. I'm not familiar with your model engine, so I'll shut up now and leave it to those who are.

 

[OmniCognateNeutronRangler]

different to my problem too (not that mine is really much of a problem). Mine is a very faint constant tapping sound. I'll leave you to the original thread....

 

[ELGRINGO]

Hi could be the actuators on the heator box a known problem on c class cars .

 

[Taxing Ken]

Thanks everybody for their suggestions. The heater box actuators seems the best bet. As everything works fine (heater, aircon, engine etc.) I'll just leave it alone on the basis of 'if it aint broke don't mend it' principle.

Ken

 

[merc888]

Ticking Noise

Ive had a ticking noise on my C240 for 3 years old and Merc dealers cant seem to figure out what the problem is.

The ticking starts when the car is warm and in motion, the noise goes faster and louder the faster i drive.

Any Ideas???