1. If the pump is hotter than the pipes going into or out of it, it means the pump is not spinning, as JohnD states above.
2. This is usually down to:
2a. The pump is jammed with sediment. OR
2b. The capacitor which gets the motor to start has failed.
3. For a jammed pump, you need to try spinning the rotor by hand. I can't remember if its the same on the pump you have, but on most:
3a. Put a tray under the pump to catch the water which will come out.
3b. Remove the black hexagon (plastic?) nut from the centre of the pump. Undo it partially, to make sure you can deal with the volume of water coming out. If there is too much, re-tighten nut and abandon attempt.
3c. With a screwdriver poked in the centre, try turning the rotor. You can't see it, you should be able to feel it.
3d. If it starts to turn, spin it a couple of times, black nut back on and hope it works properly.
3e. If it won't turn, replace the pump.
4. For a failed capacitor:
4a. If you have a multimeter with a capacitance range, test it - after isolating mains power to the extent of switching off the main consumer unit switch and cutting all power to the property.
4b. Generally in the 4 to 8 micro farad range. If outside range, replace with a 5 or 7 micro farad MOTOR rated capacitor.
5. If you have to abandon checks, you will need to call in a heating engineer, unless you feel competent to drain down the system and replace the pump yourself.
