SL320 VIBRATION IN COLD IDLE & GEAR IN 'D'

[detailas]

Greetings everybody,

I am new to the forum and I would appreciate some help with a problem I have with my 1995 SL320 (abt 100,000 miles).

Last week I had the catalytic converter and the muffler changed - all was done in official MB dealer.

Since then, whenever I start the car, lock the gear in 'D' to drive away, engine idling and I am still on the brakes, I feel a vibration / buzzing, which goes away after I rev up and drive away.

The vibr / buzz is bit embarassing so after I drive away from the house and I stop at the 1st/2nd red traffic light (while engine is still cold) I prefer to shift in 'N' (no vibration then) and wait for the green light, than to feel the uncomfortable vibration. After the engine is warmed up (2-3 miles driving) - no unpleasant sounds, etc - all is normal.

Above symptoms disappear when:

-the car is either warmed up (no problem when idling in 'D' plus brakes) -or-
-when although still cold, the revs exceed abt 1200.

This happens only in 'D' position and not in 'P' or 'N', 'R' (as one would expect) - and only when the car is cold.

Any ideas please?

++

[bwheitman]

Check the tranny mount, also make sure the exhaust mounts are not stressed, what this means is that of someone tightened the exhast to the tranny mount while cold and didn't allow it to warm up and then tighten it down, while cold you could have a heat shield or pipe vibrating against something. There is a mount that comes right off the tranny to the exhaust where the cats hook in. I would get under there while it is cold, loosen them (2 bolts) then warm the engine to operating, get back under, be very careful and tighten them back up, it is hot so don't burn yourself. Your exhaust system actually can grow up to 2 inches longer when it gets hot! Also I noticed that my SL320 makes an electronic buzzing when I make u-turns too fast. It did it when I made left turns too, but that stopped when I replaced my motor mounts and tranny mount. If you have 100k on a 95 you should probably do this even if it isn't your problem, it will drive like a new car when you do it. Is the buzzing electronic or a fast paced rattle? Good luck!
Brian

[detailas]

Brian, thanks for your advice - will check it out.

Very well put - the word is ''fast paced rattle'' - not buzzing..


George

[bwheitman]

If it is a rattle, it is likely a heat shield. There is one that mounts above the idler arm below the exhaust manifold. That one is tricky because if it gets bent it will lose it's hardness, most people bend it back, but it will rattle a bit. You could start it up while cold, put the parking brake on, block the wheels, and put it in drive, open the hood and try to isolate where the noise is coming from. A word of caution, always stand to the side of the car.. not in front. Also this works more safely if you have someone in the car with their foot on the brake. My guess is the heat shield between the cats and the underbody, when cold the cats are close to it, when it heats up it moves away, this will vibrate right into the cabin. Also on that car if you always use your parking brake when you park, put it in nuetral while you are at a stop for very long, and keep your tranny fluid changed (every 35k) that transmission will last a long time. I have 140k on mine, I drive the car every day. Every time I go look at a new one I just can't rationalize spending another 80k when the car I have drives just as good as a new one. You also have to downgrade to an SLK if you want a 6 cylinder. At 100k keep an eye on your water pump, those fail around that time. It will usually give you warnings like the area below the pump will fill with coolant, and your radiator light will come on. Don't overheat it whatever you do. You will lose your head gasket. (expensive$$$) Watch that temp gauge! They are sensitive about that. Overall a wonderful automobile, you should think about doing the work yourself, you will then see not only is it a beautiful car, but it is an engineering masterpeice. They are so simple to work on because they are built to repair and fix, meant to last a lifetime. Good luck!
Brian

[detailas]

the problem was on the engine mounts, changed them - no problem, no vibes, no rattles, etc.