E320 Issues.
 

I have a 2002 E320 that I have owned since new. A wonderfull car all around but now at about 77k later I have encountered my first issues.
1.) Hissing sound from the A/C as stated in my post before.
2.) Sterring wheel shaking at 60mph or highter. I think it is the rotors because the car does not break smooth.
3.) The molding piece on the roof has a broke plastic holder and it keeps poping up. I am not a "cob jober" or a "McGyver" and I dont want to superglue it down.

Any help would be great. Thanks.

I think that it when it just run out of Freeon and I will just add more and hissing will go away?

Do not go to Wally World or Auto Zoo to buy one of their "refill kits." They are junk. And whatever you do, NEVER put anything called a sealer into the system. NOTHING but pure 134a (and PAG-46, if the FSM calls for it under your conditions).

Guessing the refrigerant level is a good way to harm your system, particularly the compressor. Using a proper gauge set and comparing to the charts in the FSM will get you close. But as I said before, you cannot ever be sure of the quantity of refrigerant without a recovery and refill by weight.

The steering wheel shake may be the front lower control arm bushings.

Can you replace the broken mount for the trim?

I can replace the broen mount for the trip. I must get it first. Like I said I dont believe in super glue and all that crap. Its beautifull Mercedes. Not Honda Civic. I wont go to autozone and use the refrigerant things like you said. The rest(Sterrig wheel shake and AC will have to go into the shop for.)

Be sure to find a shop that is equipped to charge by weight and not pressure alone. Most American cars use a CCOT system (cycling compressor with fixed orifice tube) and the pressures are a good indication for charge level on these. Our cars use a TXV system (thermal expansion valve) and the pressure readings are not nearly as reliable for this.

Some shops charge by weight, but not all of them.

You should be able to get the replacement mounting piece from the dealer. It would be a lot cheaper to order online if you can find the part number for it, but finding that number is not easy even with the parts catalog (which you can access for free, BTW). Getting one at the dealer is probably a good idea, but keep the package in case you need another in the future - but you probably won't.