REAR KNOCKING NOISE, 1992 400E MERCEDES. CAN'T HEAR IT WHEN THE HOOD IS RAISED ONLY FROM THE INSIDE AND WHEN THE TRUNK IS RAISED. NO VIBRATIONS, JUST LOUD KNOCKING NOISE.

Might be a bearing in one of the accessories, such as the alternator or power steering pump. Try to isolate to a specific location, especially as it gets worse.

That noise is likely due to a defective radio output amplifier, pull the radio and send it in for repair.

You may be able to unlock the trunk from the door lock pump under the back seat. Remove the rear seat bottom and the insulation from the right side. You'll see the battery and a foam box. The door lock pump (PSE) is in the foam box. You need to remove the vacuum line for the trunk latch (labeled RTR or RHR on the PSE pump) and apply some air pressure to it to unlock the trunk. You should then be able to open the trunk normally, unless the trunk lock key tumbler is in the lock position, then you need a key to get in.

If you can open the hood, there is a battery pos(+) jump post in or near fuse box. Hook up a jumper box or jumper cables to power up the vehicle systems.

Yes but you must remove the rear seat back and cushion to crawl through or power up the system from under the hood at the jumper cable hook ups.

2003 Mercedes E320 fuse box location is in the trunk and under the hood an inside driver side Dash

I hear a knocking noise in the back of my car, while driving?

It could be the compressor is going out, or the clutch itself is worn out. If the AC still gets cold, then it is the clutch.

can you go through the trunk and open trunck from inside. or open hood and try to jump power to the starter hot eire and ground to engine turn key on and use remote to open trunk.......

Looks like the trunk lock has a problem and not locking with the rest , as the rear lock ia a master lock. You need to check it and replace if necessary.