Smell in airing cupboard

[micknificent7]

Sorry in advance as new to forum. I am having a problem with my central heating at moment as trying to balance the radiators in prep for winter.
I have a normal central heating system with Potterton boiler downstairs in the garage, hot water cylinder in my sons bedroom where the airing cupboard is situated and the usual pipework, timer and Myson water pump sitauted in the airing cupboard too. Yesterday I tried to balance the radiators but ran out of time without fully completing the task.At this point the central heating when turned on was operating normally and the radiators were all bled before hand too.
Today I resumed the task and turned the central heating on. However the heating did not come on even though the timer up stairs was turned to continous as per the day before. The radiators were all cold and when I went back upstairs after 30 minutes there was a strong metalic burning smell in the sons bedroom. I immediately turned the heating off and noted the pipes in the airing cupboard and casing of the pump was red hot. After doing various visual checks I went backdownstairs and noted the expansion cylinder dial showed that the water level was low.
Can anyone tell me what the smell is, why the pump and pipes were so hot and radiators cold and why the cylinder level was showing low. How do I rectify this?

 

[looneyfitter]

How low? Pump failed? Air in system?

 

[kevplumb]

How low? Pump failed? Air in system?

yup cooked pump

as for the pressure did you remember to top it up after bleeding etc

 

[micknificent7]

How low? Pump failed? Air in system?

The gauge was just displaying at 1ish, and when I was removing air from rad no actual air came out but water came out immediately. Could it have been because I initially had the rads near the top of the flow turned off to ensure heat was reaching furthest rads as per advice from British Gas Engineer when he serviced my boiler last week. Is using the system for hot water dangerous and what about the smell is this dangerous too. What should I do next as not fully up to speed on next move. I have turned off the whole system and hot water too.

 

[kevplumb]

View media item 17592
undo the screw marked bleed have a cloth handy and see if you can spin the shaft underneath with a narrow screwdriver

if the pump is cooked you will need to replace it