No Heating/Noisy Pipes

[Chrisboy]

I have oil fired central heating and during the Christmas/ New Year period when I was away from home, set the heating to come on for a couple of hours a day in an attempt to stop the pipes freezing.

When I returned home I realised that the oil had run out. I've since bought more oil but the heating won't come on. The boiler fires up as it always has and the oil tank doesn't need bleeding. The pump seems to work fine. When the thermostat on the boiler is set at a low to medium temperature no heat at all gets to the radiators although the pipe leading from the boiler gets hot. When I turn the thermostat up more (at around 140 or higher) after a couple of minutes the pipes start banging violently and I have to turn the system off in fear of causing damage to the system.

The first two radiators (upstairs) get very hot very quickly when the pipes are banging but no other radiators in the house heat at all.

I've tried everything I can think of. I've bled the radiators, bled the pump, checked all the radiators are on and checked the water level in the header tank.

I suspect there might be an airlock in the pipe somewhere after the second radiator but have no idea how to cure this or why the pipes make such a racket when the thermostat is up high and why nothing at all happens when the thermostat is lower.

Does anyone have any suggestions?
.

 

[REDSAW]

turn of the two that work, leave open the nearest rad to these two and turn of the rest.
has this rad now got hot?.
if so do this procedure to all the rads then ballance.

 

[Chrisboy]

Thanks for your suggestion. I'll try this when I get home. Should I worry about the noise the pipes make? Will this stop once water gets further around the system?

 

[REDSAW]

its possible a pipe has frozen or more likely a pipe is blocked, but shifting the heat sourse around the circuit could thaw or shift blockage.
as to dammage?. who knows without evaluating it.
but this method could sort it within an hour.
dont leave the heat in the 'hot' rad too long, just enough for it to get cosey then shut of and move to the next.