I am trying to solve a problem for my elderly father who has a ?marvellous? old Servowarm-type system (central heating only, Potterton Flamingo) with the open non-plumbed tank in the attic and 10 mm hard rubber piping. I recently put a new rad in for him (while keeping all other rads turned off to protect the MB1 already in there). The problem is that there would appear to be a large air block in the system. I have tried to approach the problem by isolating the rad nearest the boiler and opening the pump screw. I was able to get that rad hot. I then tried to go round the house in turn. All downstairs rads are full however nothing (gas or water) is coming out of the upstairs ones (yet this phenomenon occurred for a couple of them last winter despite their being red hot all the way through!). The problem remains after a whole day of trying: the boiler comes on for 3-4 min each time and then cuts out. It had a service a year ago. I allow 10-15 min each time for the system to cool down so it comes on again through the thermostat. In the early stages liquid did come out of the pump intermittently but not later on (some high pitched gurgling resulted when some of the downstairs rads were turned off). I am assuming that things get easier if the boiler is on all the time as the air will get pushed round quicker? And that cold water + air in the system is not? The pump would appear to be working OK (I used it on the highest speed). The attic tank is full and the new downstairs rad filled up in less than 20 sec so I am not sure if there is a blockage problem as there are upstairs and downstairs manifolds supplying all rads. There is a bleed point on the lowest (copper) pipe near to the boiler (which I would imagine is part of the boiler system, being copper) which lets out liquid as soon as it is opened (and is close to a microbore pipe from the tank that is attached to the copper pipe).
I am afraid that my father at the age of 88 is so set in his ways that there is no question of replacing the system so I am hoping that there might be some low-tech remedies to solve this save of bringing the plumber in.
Continually bleed the system. The under floor connections to the radiators through out the house do not facilitate air removal easily. So bleed, bleed & continue bleeding the system. Eventually you will persuade the air out & all will be OK