Noisy Central Heating- Things to check before lifting floor

Turn the heating on for the first time to find that its running noisily.

There is a pipe that vibrates that i can stop by holding it so i obviously need to put a clip on that pipe, but there also seems to be a thruming noise coming from the whole system.

The thrumming noise is loudest in the bathroom where the central heating pump is, but when the boiler and pump is running to just heat the hot water and not the radiators, the noise isn't there.

To get to the pipes under the bathroom floor i'd have to lift a load of stuck down vinyl tiles which i don't want to do unless its absolutely necessary.

Is there anything else i can do or check to reduce the noise? Turning the pump speed down works, but obviously the radiators don't get as hot and the boiler has to be turned down or you can hear water boiling in the heat exchanger.

Thanks in advance.

sounds like you have air in the heating side

let it run for a while see if it cures then try bleed the rads again.

I have done that already because the system was drained down over the summer.

Closed all the rads off to drain the system. System was drained for about 3 weeks and then refilled. All the radiator valves are now open again and i've gone round and bled all the rads. There is still a small amount of air in the system that you can hear bubbling round the system from time to time but it normally takes a couple of weeks of use before the air makes its way to a rad and can be bleed out.

I'll have another go. Need to balance the rads as well.

Rebled all the radiators and checked for air in the pump. A very small amount of air came out of some of the rads, but that was it.

The thrumming sound is still there.

The heating seems to run quite happily and quietly for a while, and then the thrumming will gradually build up to a crescendo and then calm down again.

Any more suggestions?

anyone?