radiators not heating completly

[tinkerbell]

I have a modena 102 combi Boiler...heating is set to be on at night but the Radiators are not heating properly. Seem to only be heating a little in the middle or at the top...bottoms are cold. Also the pressure Gauge on the boiler is below 1 and when the boiler kicks in every so often..it rises slightly to above 1 then stays on for approx 1 min and drops again. i have tried the only thing i can see ( lttle black tap style thing) underneath the boiler to try and get the pressure up but nothing is happening.
An help would be greatly appreciated. Its freezing in Manchester tonight!
thanks

 

[Plumber Will]

If there is a silver braided pipe anywhere on the pipes to the boiler there will be a "tap thing" at one end turn it until the pressure rises to 1.5 bar. If the pressure drops you have a leak somewhere and need it fixed.

 

[breezer]

looks just like this

 

[tinkerbell]

Thanks for that...tried it and have upped the pressure but the radiators are still cool at the bottom and warm at the top...not even very hot...
again the pump seems to come on for approx 10/15 secs then off again...about a minute later the same...
Any more ideas??

 

[Plumber Will]

The radiators will need bled but it sounds like you have other problems possibly a thermistor is needed..........best get a heating engineer to see to it.