For flushing you need to get yourself about 400 grms of tartaric acid (MB also sell citric acid to clean the radiator its part no. A 000 989 10 25) and need to dissolve it in about 7 litres water. Before pouring anything in, you should remove all old coolant by draining the radiator from the plastic drain screw (open with a washer or coin instead of screwdriver - screwdriver can break it) and there is another drain on the block hidden behind the exhaust manifold, Its reached from underneath the car, it has a nipple like end to fit a pipe onto it and would be 17 or 19mm spanner size.
Once done - remove the Tstat and install the empty housing back, flush the system with a weak soap solution (non sudsing is best) to clean out any oils in there (otherwise the acid treatment wont work) - fill the system with the acid mixture you prepared from the tank and start the engine - keep adding till it wont take anymore - keep the system full and engine running for 10 minutes with varying rpms between 700 and 2000. Drain the system again very quickly from both drains and this time do not close the drains, let them remain open, remove the upper radiator pipe and put a garden water pipe in it with running water, let the system flush, start engine to aid in flushing, you need to do this for 15 minutes or till the exiting water is no longer rusty or milky. MB specifies to close drains and run engine for 5 minutes then draining for flushing and repeating it 3 times. (they specify a T fitting to put between the top radiator pipe and radiator to connect your garden pipe to). Once clean, close drains, install thermostat and fill the system with freshly prepared MB coolant - fill the system from the expansion bottle till it stabilises level, fill the radiator from the top radiator pipe till you see its coming to flow out, install radiator pipe (this step ensures you dont get a stupidly large air bubble in the system). Start engine and warm it up - notice temp gauge and feel the pipes and radiator - no irregularities means no air locks and you are good to go.
BEWARE OF ONE THING IN THIS PROCEDURE. If you have heavy rust, you might remove rust that is blocking corroded holes in the system including the heater. You may just choose to drain and fill with new coolant with the above procedure. Choose your remedy wisely.
Brake bleeding is the same as any other car but if your pedal is still spongy then there is some air somewhere in the system, You might have overstroked the brake master cylinder when bleeding - this happens when the pedal is stroked to the floor of an old car during bleeding, it causes the MC pistons to reach into corroded areas of the MC and tearing of seals, causing loss of pressure (usually happens on cars whose brake fluid is not changed in years).
May I ask when was the last time you changed the rubber brake pipes near your wheel calipers and are the rest of the calipers greased etc? Old pipes cause strangely soft brakes - and you driving an MB already know that these cars do not nose dive like jap cars - as the rear suspension tries to compensate the dive hence it bites into the ground on all fours. (quite strange to explain) - hence their brakes tend to feel weak but if you notice how quick the speedo drops you'll see it stops far quicker than a Jap car.
anyway nervous ABS is usually a dirty sensor or bad sensor or even a loose plug on the wheel sensor, clean check and it would solve itself, the components are very robust if you dont hit them with a hammer.
