Pump causing pipe noise??

I have a microbore open vent heating system with Ideal Elan RS50 propane boiler. The boiler has 2 thermostat settings (low 60C and high 82C). At low I have no problems. When set to high as the temperature reaches close to cut-off there is a continual banging in the pipes leading from the boiler. My pump has 3 settings, and I have found that if I set this to the fastest setting the banging stops (equally on setting 1 the banging gets louder). However, sometimes even setting 3 results in banging.

In addition the pump sounds noiser than it used to and when the heating switches off, you can occasionally hear gurgling water through the pipes near the pump. All the radiators work and there are no airlocks (only some cold spots at the bottom of 1 or 2 rads which I presume are a bit sludgy).

Any idea what I can do? Does the pump need replacing? If so, should I put a more powerful pump as I know microbore tends to wear them out more (it is a 3 year old Grundflos 15-50). Thanks for any advice

I am not a plumber or heating engineer
but as you said

helsdon said:

All the radiators work and there are no airlocks (only some cold spots at the bottom of 1 or 2 rads which I presume are a bit sludgy).

Click to expand...

I should say that your system is more than "a bit sludgy" Try flushing the whole system and adding an inhibitor.

The cold spots can't be the problem - they have been there ever since we moved in 2 years ago. The banging pipes and noisy pump have only just started. Besides, I have already flushed these rads out and the water is pretty clean. I think the cold spots are just because the water flow is slow due to the microbore.

Any other possible causes? Or should I flush the whole system?

I would suggest you flush the whole system.