My 2005 CLK 500 will rarely make a very (VERY) loud noise a second or two after ignition, continuing until the ignition is turned off. It only happens once every three months or so, and sounds like a jackhammer on a metal pan. When the ignition is turned off, and then restarted, the noise usually doesn't recur, and the car runs without further problems. The dealer has checked it out repeatedly, and can find nothing wrong. Any suggestions?? Anyone had a similar problem??

 

Very unusual!!
All depends on.....
very (VERY) loud noise a second or two after ignition, continuing until the ignition is turned off.
After turning on the ignition or starting the car? i.e. Engine running.
Try to be a bit more specific.
Jackhammer suggests heavy rythmic. Correct?
In gear or out of gear or both.

Any common factors when it occurs.
After standing X days?
Cold?
etc.

Whatever the cause the car shouldn't be making a noise to alarm you. Presumably the dealer can't help because presumably he hasn't experienced the sound. We likewise.

Since the car is under warranty what happens if you try to move the car when its making the noise?

I assume that there is oil in the engine?

Stuart

 

Thanks for your reply to my problem. The engine is running while the noise is going on, though I admit that the noise has been so alarming, my immediate response has been to turn it off. It is, indeed, rhythmic. The car is always started in "park", and the noise does not seem to be related to the length of time since the car was last driven, time of day, weather, etc. It's occurred after having been driven an hour earlier, and it's occurred when being started for the first time in the morning. The car has had its recommended maintenance, including oil changes, at the dealership. It's been doing this, occasionally, for over a year.

Any other questions or suggestions?

smc

 

Its all down to the noise! ....Although if it has been doing it for a year I suspect that it must be something external rather than internal. Has a mechanic left a screwdriver loose in the engine bay or similar?? Can you recall what event happened immediately prior to the first occurrence?

To state the obvious: If the noise is sufficiently LOUD to cause you to turn the engine OFF immediately there is something obviously very wrong.

Stuart

 

Just a thaught - If teh noise is comming from the rear of the car, it may be the muffler tapping against the car.