Hot Rads downstairs Cold Upstairs

[matts_notaplumber]

Hi guys, having read several threads here I have a similar problem with cold rads upsatirs hot downstairs.
It only started 2 days ago, nothing has changed with my system.
I haven't done anything to any of the settings. I have followed a few of the threads, bled the rads water comes through and no air at comes out.
I have checked the feeder/expansion tank in loft plenty of water in there.
I have done a quick test as suggested.ie turning stat valves down on working rads, and voila that works, hot rads upstairs.
Does that mean its a balancing issue
If so do I have to mess about with the LSV aswell as turnin Rad Stats down
And why as this only just happened now, we have lived in the house for 2 years and its never happened before
Could it mean a more serious underlying problem?
PS the boiler was brand new when we moved in 2 years ago. Not a Combi. There is no air at all coming through system, I did a lot of work to the house last year, so lots of rads were changed/replaced/removed for a while etc, I did have a problem with a new towel rad in the bathroom for a while filling with air constatly but kept bleeding it and it now never fills with air.
Any ideas Forgive me If i have forgotten to mention anything as I am new to this amazing forum, some fantastic help advice.

 

[ChrisR]

Certainly the lockshields do need to be about right, even when using trv's. Try them just half a turn open.
Look at the pump speed for experiments. It could be that it has just slowed down or got some sludge in its vanes.

 

[matts_notaplumber]

Thanks for your response

can i check the pump by just undoing the big screw in the middle of the pump?
Is there any reason why its just suddenly happened?

The other problem is the some of the LSV's leak when not fully opened or not fully closed!!! ERrrr not too keen on changing them til summer and I can take my time draining system etc..

 

[matts_notaplumber]

Thanks for your response

can i check the pump by just undoing the big screw in the middle of the pump?
Is there any reason why its just suddenly happened?

The other problem is the some of the LSV's leak when not fully opened or not fully closed!!! ERrrr not too keen on changing them til summer and I can take my time draining system etc..

 

[ChrisR]

No!

Capacitors dry up and the pump slows.
Gunge can get caught in the impeller.
Isolate pump if the valves work and remove the head - allen screws usually. Start pump and see if you can stop it with less than a lot of effort. If so it's knackd.
Use a thin screwdriver to probe between the discs of the impeller.

If there's a nut round the spindle of the lsv's tightening it should slow the leak. If not they're cheap junk. (Or expensive junk like some current Peglers)

 

[matts_notaplumber]

so thats no, don't unscrew the big brass screw???
good tip about lsv nut, i will try that.
but do i have remove pump comp[letey???

 

[kevplumb]

Isolate pump if the valves work and remove the head - allen screws usually

 

[ChrisR]

so thats no, don't unscrew the big brass screw???

Correct. It allows you to check/turn the shaft, and let air out, that's all.

but do i have remove pump comp[letey???

NO,

Isolate pump if the valves work and remove the head - allen screws usually

I usually tap a penknife into the join in the casting with the screws loose but still in, in case the iso valves haven't shut properly.

 

[matts_notaplumber]

Thanks again, i will try this approach tomorrow.
however after adjusting the Thermostat valves on a couple of downstairs rads all seems hunky dorey!