Hello my friends! I have a question regarding the 2001 E320 base model-97000 milege- I own, I hear growling noise coming from the rear end especially loud when car is cold. At first I suggested it was loose muffler but after close inspection everything was fine. the idle is also rough and shaky I checked the motor mounts and they are fine. I also noticed the temperature gauge is rising quite often recently...
This car I bought from a woman in november and seemed everything ok, I'm not quite sure about service and maintanance it had in past, but seemed everything ok. tranny shifts smooth, engine oil is same level and colour. The first thing I did when I bought flush the engine and replaced an oil, filter...
I wanted to flush and replace transmission oil but dealer advised me not to, unless I'm looking for a trouble and that's about it.

My question is what are possible causes of all this? I mean it's obvious that this rough idle causes vibration, but can't find the source of this growling noise and solution of this problem.
Thanks in advance to everybody.
God bless you all.