clk 320 "chirping"
 

I'm trying to figure out where this sound is coming from. Chirping, just like a bird, occurs during driving, over bumps, over smooth surfaces and even can be heard when I close the front doors on both sides of the car. Thought it might be the serpentine belt, but it seems tight and in good shape. Recently replaced front & rear shocks, rear springs (left one cracked) and ball joints; tie rods are leaking & will be replaced next week. Thanks for your thoughts.

can you hear the noise with the car stationary? and with the HVAC (a/c heater) off ?

Yes, sometimes the noise can be heard when the car is stationary, motor running & hvac off.

it could be anything from a damaged engine mount to bearing on an alternator.

one thing, do a search on this forum for accessory belt tensioner or BELT TENSIONER.

If you have a stethoscope and are extremely careful you can listen to alternator, belt tensoner, water pump.


When you mention closing the front doors and hearing it I think windshield mounting or door straps even hood latch or inside rear view mirror.

Hopefully I mentioned some items you can eliminate.

Lots of times a helper who can listen to the car from the outside as you drive by can clue you in.

belt churp
 

dump water on the belts while running and see if the noise stops, if so it is belt noise

My indie heard the noise last weekend and said I need the emergency brake repair kit (12442008720). Shouldn't this be checked when rear rotors are replaced, or could something have gotten loose when he replaced those rear rotors?

often to take off the rear rotors, you need to loosen the parking brake by turning an adjuster nut accessed through a lug nut whole.

I know there have been times when I'd get the rear parking brake chirp when it was engaged and I dropped into the car seat.

I know that sometimes the parking brake release handle vibrates when my car is idling - but I have over 100k miles - and it is just a wear thing.

Cat breaking up?
 

Well, now I've been told that its the catalytic converter innards, probably the honeycomb material loosening. The indie heard the noise when he gunned the engine, causing greater exhaust gas pressure through the system. Of course. the MB warranty expired a while ago. Taking it to the dealer to see how much holiday spirit they have.

when you get some time do a google search for STAR TECH MAGAZINE, go to the archives and research catalytic converters, also view your Mercedes Warranty booklet for your car and look up federal emission warranty items.

some emission parts are warrantied for as long as eight years, I think.

Vehicle was purchased 2/99, so 8 yr emissions warranty technically has expired. This morning I arranged a MB dealer inspection, scheduled for this friday, and I will discuss the matter then & keep you posted. Thanks.

also read that article in STAR TECH MAGAZINE which is a Mercedes Benz Company publication.
The jist of the article was- many time there is an associated issue which cause catalytic converter breakage.
I always like to have as much information when I go into the dealer, so I can make a complete nuisance of myself at the service department.

I know this sounds crazy, but I had the exact same chirping noise in my E430.

One day I put the rear seat headrests (all three) in the up position, and noticed that the chirping disappeared completely.

Upon examination, when the headrests are in the down position, they bounce up and down over bumps, and make a squeaking noise.

I don't like keeping headrests in the up position because it blocks my rear view, so I found that when I angle the head rest when in the down position, it stops them from bouncing.

I would spray some water on the belts with a plant sprayer just to make sure it is not the belts.

This may sound strange, but it’s worth a try.
My wife’s 1993 300E had a strange chirping, almost cricket like sound coming from it regularly. It was hard to tell where it was coming from and it puzzled me for a long time until I slammed the trunk one day. The noise was actually created by the trunk closing mechanism, a spring as I remember. It was loud and weird. It sounds like your noise is coming from under the hood but I thought it was worth passing on the information.
Good Luck