Unusual noise upon start up

[cobra7]

A very weird humming noise has developed upon start up. Car ticks over fine - the noise appears to be coming from the rear but is not that noticable from outside. Disappears after a minute or two but is still a concern.

My car was in last week for some work - new Air Mass Sensor, fuel filter, lambda sensors - has been driving better than ever but now this damn noise has started. Has anyone experienced the same? Should i be concerned??

 

[BlackC55]

What kind of noise is it?

A hummmm?

If it is it could be the fuel pump

 

[p3tchy]

I'd say fuel pump too.

 

[cobra7]

Thanks for your reply chap

Can only describe it as sounding like a quiet vacuum cleaner, has a very slight hum to it - very odd! Comes from the rear, louder inside, barely noticeable outside.

You mention fuel pump - could that be as a result of having the fuel filter replaced last week??

 

[BlackC55]

Yes. They can make a noise after. Quite often the hum when they are going to fail.

 

[cobra7]

And failing would be a bad thing?

So need to get back in pronto in your opinion??

 

[BlackC55]

Yes

 

[cobra7]

Sh1t - more expense then!! Expensive fix??

 

[BlackC55]

Of course. Its a Mercedes-Benz

 

[cobra7]

lol - cheers chap, appreciate your input here

 

[p3tchy]

You'll hear it inside as the access panel is sometimes under the back seats, not so much outside as the sound of the engine/exhaust drown it out.

If the fuel filter was really clogged up then the pump would have been working harder to deliver the correct pressure now it can spin more freely it's showing signs of wear. That's only a possibilty though.

 

[martyz]

Are you sure it's not the central locking pump?,mine sometimes runs on for a while
when the mood takes it.

 

[cobra7]

Wouldn't have a clue Martyz, I'm unfortunately lacking in the mechanical sense i must be a mechanics dream!!

 

[martyz]

Sit in your car without starting the engine, lock and unlock the car and listen
to see if it's the noise you have been hearing.(don't move about inside when locked,the alarm might go off).

 

[smurgewurfler]

Or it might be the air pump.