Hadn't used the dishwasher for many months. When I did there was a burning type smell and then brown water which eventually became clear leaked from underneath unit. Any ideas

If it's been sitting that long, the seals are probably dry and the impeller was not turning. Unless it's a fairly new DW, time for a new one I'm afraid.

I have to agree with ma0641. Time to give your old washer a nice send off and replace it. You could have the old washer repaired but it would be costly and you would still be left with the old washer. If the motor simply hummed the it was the motor windings burning up that you smelled. Replace the washer! Good luck, Tom