Rattling noise at startup: Audio File Attch'd
 

I for the life of me can't find the source of this rattling noise. I was holding the recorder near the front jack point on the driver's side. As you'll note from the file, the sound almost completely disappears when even the tiniest amount of throttle is applied. But comes back with avengence when at idle.
The noise is loudest on either side of the car near the front jackpoints. It is substantially quieter when you are standing by the front bumper.

http://home.comcast.net/~grindmarc/merc_rattle.MP3

Thanks in advance everyone that replies.
I rebuilt the steering pump over the weekend, so I'm ready to tackle this one!

Holy cow :eek: :D Sounds like maybe the muffler pipe or something along there rattling against the car or a metal shield or something. Sounds like a rather thin piece of metal is doing the vibrating. Others with SDL's will probably know better what it could be....

That engine sounds sweet though! :D Makes me want one.....(only in addition to the SD/617 though)

Grinding and rattle
 

Dear Grind, I would want to rule out a problem with the timing chain first...may I suggest putting a 2 foot by 3/4 inch wooden dowel to the front case of the engine and see if the noise is coming from there. Once you rule out that critical potential problem then you could look to see if it may be a loose exhaust conection somewhere. Good luck.

Antonino

Hmmmm, I wonder if it is a bad motor mount making the vibration and sound worse?

Motor mounts are good! You should have heard it BEFORE I replaced the mounts! LOL You would have heard my teeth chattering on the sound clip!

I will look over the exhaust system very carefully tomorrow.

Antonio, I don't quite understand the dowel suggestion. Can you please provide more detail? Do I hold it against the case? Then what?

you should also check the air filter mounts. but I'll bet you it's exhaust related

Place one end of the dowel against the part you want to listen to and put your ear against the other end so that it seals the ear shut. Then you hear the sound conducted by the wood, not through the air. Kind of like a stethoscope. You can also use a long screwdriver or the like. You'll know which end to put against your ear after one or two tries !! Steve

I do believe the 603's did away with that annoying little problem by putting the air filter off to the side instead of perched on top of the engine.

Check to see if maybe a heat shield has shaken a bolt loose. The shield on my '84 that protects the starter from the turbo/exhaust has lost one bolt and it'll vibrate around 1200 rpm as I'm accelerating or decelerating.

Man, am I embarassed.

It was a u-bolt on the exhaust just before the cat. It needed about 3/4 of a turn for the rattling to stop. I cannot get over how much noise that single bolt created.

And now the sweet, sweet purr of a rattle-free 300SDL.
http://home.comcast.net/~grindmarc/merc_fixed.MP3

Thanks for the help everyone! I think I spent about 4x more time posting this thread than it took me to fix the problem! :silly: