noisy air flow sensor ?

[mk11]

HI all, thanks for letting me join - my first forum so please bear with me.
I have E200 kompressor estate 2004. Always had mercs but this one is my first petrol motor for quite a while. Have noticed when the blowers are on with the air con I get a low dronning noise coming from the engine on tick-over. Does any one know what this could be ?

 

[lynall]

Welcome i think we need more info pretty good forum this one.

Ie blowers = in car fan ?

Lights on, at a standstill or driving, revs constant etc.

Engine ticking over air con off steady rpm, then switch a/c on what happens then?



Lynall

 

[mk11]

HI
Have investigate with engine running as advised, the noise is steady whatever the engine is doing so I think it might be the sensor - have taken the filter out and if you
cover the filter grill - where hand is - the noise gets less - although in the cabin there is no loss of noise.
Could it be the motor to the sensor needs replacing ?

 

[alexander patie]

??err, i am stumped here. the sensor does not and will not make a noise. it has no motor in it, no moving parts at all.

the droning noise, it could be a poly belt noise. are you saying it only does it with the aircon (refrigeration) on? have a look at the drive belt on the front of the engine, does it seem to be vibrating?

other thoughts, if you ONLY hear the noise with the blower on, it could be the blower itself. might have a badly fitted cabin filter letting leaves into the blades causing vibration. but put the air filter back, please.

 

[lynall]

As Alex says that is the maf sensor housing and cannot and does not make a noise, all it does is measure the amount of air being sucked into the engine.

Have you tried with the engine running (watching out for rotating parts) moving the airbox and anything that could make a noise, ie give everything a good wiggle and see if the noise/note changes.

If nothing may be worth having a pro look over it just in case, a stitch in time etc.

Try it with all the plastic engine covers removed, had this years ago on a landrover and was sound deadening plastic jobby making the noise due to a broken fitting.


Lynall

 

[alexander patie]

MKII, you are very close to our company (near needham market), call by for a free check. PM me for details if you wish to do this.

 

[mk11]

Hi Alexander - many thanks - would love to take you up on offer - cant pm as dont have enough posts - could you call 07860 254036 - maurice. Very much appreciated.

 

[Rory]

HI all, thanks for letting me join - my first forum so please bear with me.
I have E200 kompressor estate 2004. Always had mercs but this one is my first petrol motor for quite a while. Have noticed when the blowers are on with the air con I get a low dronning noise coming from the engine on tick-over. Does any one know what this could be ?

Sorry if if I'm missing something here, but isn't the noise the radiator cooling fan? On most cars they run all the time when the a/c is on.

 

[mk11]

Hi
goodness knows what it is - but it's quite a drone and have never had a merc making this noise - i cant beleive it is "normal" use noise .My recent past mercs have been diesels and they didnt make anything like it- and they were 10 yrs older !

 

[lynall]

Ref the ac fan, most modern cars, only come on when the outside air temp is high enough for them to be needed, never heard mine running (W210), my old disco was also the same only ran when outside temp stonking hot.

Older cars used to come on at same time as compressor.



Lynall

 

[alexander patie]

well mk11 came to see us today and we found his noises. the one under the bonnet was a red herring, just the supercharger intake noise and not overly loud.

the noise that was driving himreally wild was from the aircon pump, transmitted through the pipework into the cars climate system. the noise at the pump was minimal and this proved a little tricky to pin down, especially as pressing the 'ac off' button made no difference, but pressin the '0' (climate control of) button immediately stopped it.

with star i found that the pump is actually pumping at 30%, even with the 'ac off'!! a quick change of the coding made this drop to 0% with the 'ac off', which is what i expected it to do!! now he can use the climate with ac off and no noise, rather than having to turn the whole lot off. the full cure would be a new ac pump but mk11 is thinking about it.. a very nice chap and an interesting problem.

 

[Rory]

.... especially as pressing the 'ac off' button made no difference, but pressin the '0' (climate control of) button immediately stopped it.

with star i found that the pump is actually pumping at 30%, even with the 'ac off'!! a quick change of the coding made this drop to 0% with the 'ac off', which is what i expected it to do!!

That's interesting - I have a facelift (late 2004) W203 and I'm of the school that only uses the a/c when necessary.

I've noticed in my car (my first Mercedes) that I can turn the a/c off and it still appears to be on. Then some time later (a few mins, but seems a variable amount of time) the car will suddenly mist up as, I guess, the a/c at last decides to turn itself off. It's obviously on some sort of cycle, and it occurs to me that perhaps the 30% you mention is designed-in to stop the sudden misting when the a/c goes off?

 

[lynall]

Well at least its fixed albeit temporarily



Lynall

 

[alexander patie]

interesting thought rory, there will be a reason and i think you may be on the money there.

 

[mk11]

many many thanks to Alexander for sorting out the noise - as he said was driving me mad - and to have a mercedes you would expect better.Am still thinking about a change of estate car so will leave as is for now. Excellent start to my forum membership - very impressed with assistance and help.