Andy having read your comments, and considering my situation, I have
decided that I will do a full system drain, flush everything I can,
take the opportunity to me a radiator and then fill her back up.

ONE MORE QUESTION though...

I can seem to find any draincock lower than the ground floor rad
valves. Do modern houses *always* have one fitted at the lowest level
of the system??? Usually outside or on the patio? If there is no
other draincock how do I get the water out of the bottom of the
system? I am wondering because when I try and move a ground floor
radiator (pipes in screed) I am looking at it all draining out
there...arrrghhhhh

thanks

Tim


They do run a little warm when active, simply because the motor is
powered in a stalled condition to hold the valve open.

I thought this might be the case...still I will check and see if it
turns easily

I just looked through the earlier thread now, and I think it would be
worth doing a check as to whether the heat exchanger has a build up of
assorted sludge. This tends to create local boiling in the exchanger
and hence the noise. Is it a cast iron type of exchanger or low
water content (i.e. tubes)? I think that I would work out a way to
flush it through. I'd also take a look at a radiator to get an
idea of whether there is significant sludging in the system in
general. If you are thinking of adding TRVs, then it makes sense
to do a thorough clean out at the same time.

Looks like I will do a full system drain down then. Ideal time to
have a good look at the boiler and heat exchanger.

While you have the system drained down, you could fit drain cocks and
lever ball valves to either side of the boiler to be able to isolate
it and also to be able to hook up hoses to flush it through. If you
do this, I would add two further things. First of all a pressure
release safety valve on the boiler side of any valves, and secondly a
strainer on the return side to catch any circulating grot.

Good advice - it was soo simple changing the pump because someone did
the job properly and fitted gate valves either side

Also, I think you need to consider the age of the boiler. It is
getting towards the end of its useful life and if you end up having to
do power flushes or heat exchanger replacements then the costs are
going to add up quite rapidly to the point where it really is throwing
good money after bad. I wouldn't spend any more than £100-200 on
fixing this.

Fair point too

Personally, unless you can achieve an easy fix, I would dump the
boiler and concentrate on cleaning up the rest of the system and
fitting the TRVs.