Car dies when driving at normal temp and all gages are normal wont start or have any power to anything and fan is running until engine cools (when key is on) slk 230 kompressor

Did you check for applicable trouble codes? Anything? Some of the national brand auto stores will check codes for free.
Check the coolant temp sensor, if you haven't already? Some makes and models if you turn on the ac, the fan/s will run. If you unplug the coolant temp sensor, the fan may run.
I might want to use non--contact infrared temp gun just to double-check temp gage.
Have you ever checked thermostat or coolant flow through the radiator. I understand it only heats at idle.

the usual suspects are:
stuck shut thermostat
clogged raiator
dead water pump
low coolant level
it's sunday, rovers don't work on sunday.
Then again, maybe its wednesday, rovers take half a day then.

the one thing in your statment is the knockes/knocking this what is known as the big ends and indicates the engine is under pressure and needs a lot of repair.If when you start the engine when cold if you stand at the back of the car and if the smoke coming out of the exhaust has a blue tint/ie like a old ladys hair tint ,as im sure you will see.[bottom line] the engine needs replaced.adrian,,,,

You probably need to bleed the cooling system properly.

Open the cooling system bleeder screws.

Slowly fill the cooling system with a 50/50 coolant mixture until coolant runs freely out of bleeder screws.
Close the cooling system bleeder screws
Install the coolant pressure cap
Start the engine.
Run the engine at 2,000 - 2,500 RPM until the engine reaches normal operating temperature. (midway on gauge)
Allow the engine to idle for 3 minutes.
Shut the engine off.
Allow the engine to completely cool.
Top off the coolant as necessary.
Run engine again at 2000 - 2500 RPM until the engine reaches normal operating temperature.
Allow engine to idle until cooling fans come on. It should come on with the gauge about 3/4 of the way to red. - if it gets to where is touches the red, shut down immediately.
When the fan comes on, put your hand behind the fan and observe the temperature of the air coming from the fan. It should feel hot. If it is blowing cold air, the coolant is not circulating through the radiator like it should. This could be caused by lots of things including an improper/defective thermostat, corroded water pump impeller, or a blown head gasket.

A lot of cars have the fans running after the fact, they just cool down the temp a little, have you checked your coolant lately? Keep an eye on the temp gage on the dash, make sure it doesn't go very far, It should be very constant when running.

Check out clarks-garage.com he has a complete troubleshooting guide for your cooling system along with a schematic. In short, check the low speed resistor on the firewall. Should be around one ohm.

if i disconect temp sensor fans come on cool engine but then no temp gauge

That's what I'd expect after unplugging.
This is sounding like a bad coolant temp sensor. Test it or replace it before you do anything else. Read this post on how to test an engine coolant temperature sensor

Test engine coolant temperature sensor Ricks Free Auto Repair Advice

replace the fuel filter

why does the cooling fan start working as soon as i start the car and doesn't shut off until i turn off the car?

The next time you start your car wait until the temp gage starts to go up past the normal level and turn your heat on full blast. if the temp starts to go down and stayes there while driving than you need to get a thermaostat that opens well before the one you have. also check to make sure you have filled you raditor and overflow tank but please remember that you can only fill your over flow tank to a certain spot when the engine is cold(before you start it) and when it is hot (when it has been running).
If this does not fix the problem please let me know and i will assist you in another direction.