Mercedes Benz heater going?

mercedes-benz
c-class

#1

I have been hearing a loud noise coming from heater when I first turn on the car in the am and it is cold. I live in the Northeast so that’s just about every am. It is loud blowing noise and I’m wondering if my heating system is going. Anyone else experienced this with 2005 C240 Benz.

On another note, the brakes also seem to be making a noise when I have to use them-- when the car is cold and then it goes away once the car is warmed up. Any idea what this could be attributed to and is it something I need to address right away?
Thanks for reading,


#2

Depends on what the noise is exactly. GM used to be famous for blower noise in the morning until the blower motor itself got warmed up a little. It was just the lube on the bearings and didn’t really affect the longevity, just made a racket for a minute or two in the morning when cold.


#3

My Ford truck’s heater blower makes a racket when it gets really cold too. Either the motor or cage bearings are going dry, or thermal shrinkage is causing some kind of interference. A mechanic should remove the motor and blower cage for a look-see.


#4

Thank you for the replies:) if it is lube on the bearings or motor, do you think this is an expensive fix? I just bought the car and hoping not to have to pay for expensive repairs right away.


#5

@SherryMerc: Unfortunately these cars aren’t really known for being trouble-free. I don’t know what a blower motor runs for your car or how hard it is to change. When temps are very cold though, a lot of machinery complains at start up. Can you describe what kind of noise you’re getting?

Also, re. your brakes, if you drive in snow and salt (or even rain) and then park the car overnight, a coating of rust can form on the surface of your brake rotors and cause a noise and grinding feel for the first couple of stops. This is normal and harmless. If your brakes are continually grinding though, making other noises, pulling to one side, or you’re noticing that they’re less effective or you need to press harder than normal to stop the car, it would be best to get them checked out asap.


#6

Oblivion- thanks for the reply! The noise coming from heater is just a blowing noise (the same as any car if you turn heater on high) this one is …just a louder than “typical” blowing sound. It like it is ampted up several decibels. Like I mentioned, it does go away and the days it has been in 40ies it goes away quickly. But days in the 30’s or 20’s - it takes longer to go Away. I usually turn the heater off until car is a bit warmer rather than listen to the loud sound or turn up my radio:)
Thanks for the info on rust from snow, salt, etc. it sounds like that very likely could be the case. I recall a mechanic I used years ago with my previous car had scraped or /buffed the rust off. Does that make sense?


#7

@SherryMerc: You wouldn’t normally have to buff the rust off your rotors unless the car sat for a long time and the rotors were really badly rusted or pitted. Just driving and using the brakes will eliminate the small amount of rust that naturally develops after driving on a damp day.

Re. the heater, I wonder if you have a blend door that’s sticking or sluggish when it’s cold, so it takes some time for it to move and properly direct the air. If you have automatic climate control, it may be intentionally diverting the air when it senses the car is ice cold to avoid discomfort or icing up the windows and the result is the blower seems louder. This could be normal if the system is programmed this way and you’re using the automatic setting.


#8

I would not assume that it’s the heating system. Start by opening the hood and listening when the noise is occurring to see if you can tell from where it’s coming. Only by trying will you be able to determine the sound’s source. Sounds coming from under the hood often sound like they’re coming from under the dash.

Or take it to a Merc shop and ask them to do a diagnosis only. They can tell you exactly where it’s coming from and give you a repair estimate. It might cost you perhaps $150 or so, but at least you’ll know.


#9

Several decibels? 3 db is twice as loud. Interesting comment.


#10

I don’t know the details of Benz’s climate control system, but in cars that expensive, they often have automatic systems. In such you simply set the desired temp and the system does the rest. In those cases the fan speed is automatically regulated based on how far it needs to go to get to your preset temp.
On a cold morning, and this has been an unusually cold winter, it will need to blow a lot of air to bring cabin temp up to your warm preset. Could it be that that is what you are hearing?
As for the brakes, I agree with someone above. Sounds like surface rust being ground off by the first few brake applications of the morning. Check your service records. How many miles ago was the last brake service?


#11

And a 3 dB increase produces twice the VOLUME of sound, but it is not perceived by our ears to twice as loud. Most audio engineers agree that it takes a 10dB increase for us to perceive a doubling of noise level.


#12

@Oblivion - I brought the car to mechanic around the corner. He listened to the sound and said he also thought it was the blend door that’s the problem, so I made an appointment to bring to a mechanic that services Merc’s. (He did not!). I should know something tomorrow after I drop it off for diagnosis. BTW, I do not have automatic climate control.
The mechanic would do a brake check on the merc for $49.95 and if it needs brakes, the $$ goes toward the brake job cost. I thought that sounded reasonable. The rear brake pads and rotors were done 2 years ago 5/2012) but the put in after market parts and the previous driver was hard on the brakes …did I mention I bought the car from my mother in law???
Thanks for your help.


#13

@SherryMerc

You’re wrong about the automatic climate control

I used to work on those cars, and the US spec C240s all had a control panel with an auto button

Do you have a gray market . . . or Canadian . . . car?

The glovebox is in the passenger footwell. Drop it and see if there’s a bunch of leaves in there

I recall that there were numerous technical service bulletins pertaining to the blower motor for your car. There were updated blower motors and blower control modules. I’m going to guess you don’t have the latest and greatest

Another heads up . . . your car was well known for having problems with the ac “stepper motors” and linkages seizing up and breaking. In some cases, when they would act up, the case would crack. Have you been hearing clicking noises from behind the dash?

If the guy messes around with the ac stepper motors, make absolutely sure he knows how to normalize them after the repair. Otherwise, they won’t work correctly. It’s not like an American car. They will NOT figure out their home position on their own.

As for the brakes, I highly recommend sticking with genuine Mercedes-Benz parts, or at least German parts. Make sure the guy drives the car on the freeway. He won’t feel a warped rotor applying the brakes at 30mph.