Buzzing from petrol tank on C209 CLK320 - Help!!

[Foghorn62]

I purchased a 2002 CLK320 Petrol (71K miles) (VIN=WDB2093652F034126) in May this year and have noticed an increasingly annoying loud buzzing/hum coming from the petrol tank that can only be stopped by turning the engine off.

Whilst on holiday last week, I stopped at the Harrogate MB dealer and asked an engineer to take a quick look. He listened to it and thought the in-tank fuel pump was on its way out, pointing me to their parts department who quoted me £231 for just the motor. I ended up buying the whole assembly from EuroCarParts, paying £118 for the Bosch unit.

I fitted it on Sunday and took the car for a run. The noise only starts when I have been driving 20+ miles or I give the car some "welly", needless to say that within 3 miles the noise was back. I took it to my local village garage on Monday with the noise present and after getting under the car, he confirmed the noise is definitely coming from the petrol tank area, so I decided to check the Sender Unit on the passenger side of the tank and on inspection couldn't see anything wrong with that either. Disconnecting the wiring harness plug from the Sender Unit stops the noise immediately, so I know the noise is related to the fuel system.

Still left with the loud buzzing, I am left with only two things - Either the relay is playing up or, more likely (if I have one fitted) the fuel filter needs replacing and this is affecting the fuel rate that the pump is trying to send to the engine when fuel demand is high.

Which is where I could do with your help.

• Firstly, has anybody come across such symptoms before?
• Secondly, given my VIN No. above, can anybody confirm if I have an external fuel filter that might need replacing and if so, what the part number is and where is the filter located?
• Thirdly, is changing the filter a simple task, or should I be looking at getting the dealer to replace it?

Any help would be greatly appreciated.

Thanks,

Mike.

 

[dozypillock]

Not had this problem, and wish I could help as probably have identical car. Mine is on 90k now, and having spent fortune on gearbox, now drives beautifully. I frequent these forums to learn of potential problems to come.
I would suggest asking for advise to a local MB expert, as they can be very useful, and most will offer advice free. Just advise what you have already done/investigated etc as most will just say it needs to go on a STAR to diagnose. It sounds like you are on the right track anyway, and I wish I could help you with a fuel filter location.
When you find it, please update the thread, to help others.

Neil

 

[Foghorn62]

I found the following article on an American site, which explains where the fuel filter is located and how to replace it :-
Pelican Mercedes-Benz Tech Article - Replacing Your Fuel Filter - C230 / E320 / S320 / ML320 / CLK320 / SLK320

Even though filed in the W203 folder, it does state that is still applicable to the W209.

I've ordered a Bosch fuel filter and four hose clips from EuroCarParts and we'll see if this clears the buzzing noise. I'll post my results here when fitted in a couple of weeks

 

[pcthrillrider]

blocked fuel filter?

 

[Alps]

will be the fuel pump

 

[PobodY]

will be the fuel pump

This, absolutely. - I suspect the problem was solved about 2 years ago, probably with a new pump.

The filter would need to be near-completely clogged to be the root cause, and it's never taken me more than about 5 minutes to swap one out in the past (although I haven't looked at the CLK).