One rad at a time?

[tod4]

Last winter I thought I had a problem with my 3 way valve. For an unknown reason (to me) only one or at best two rads would got hot at a time. I've got a boiler in my kitchen. Pump upstairs. Four rads in the house, two up two down. Every thing used to fine.
I found if I forced the gear (not the lever) over in the three way valve I could get some sort of heating in two rads. So presumed it was the 3 way valve. I've now had that replaced and am waiting for an electrician to wire it up, but its been fitted. If I move the manual lever over I can get the same as I had before one or two rads get hot although one of them is only luke warm. I’ve noticed that the rad nearest to the pump gets very hot. If I turn that one off the next nearest gets hot and so on. But no matter what I do the last one which I think is the furthest pipe run won’t get much more than just off cold. The hot water (lever in the normal position) works fine. The hot water tank is about 2 feet from the pump.
I can hear the pump running. The system was drained to have the new 3 way valve fitted. I have bled every rad and they all run clear with no air.
So what’s wrong? Could it be the pump is no good, could it work but not as well as it should? I had it replaced about 15 years ago. Last time it went it made some awful noises this time is sounds fine.
Suggestions please.

 

[andytheplumber]

Since the pump is only 15 years old i cant see this as the problem.

If you take the average T.V, car, washing machine, dishwasher, toaster, play station, and so on. Are these expected to last 15 years.

You might consider powerflushing, or changining the rad valves

 

[tod4]

Van 27 years old, motor bike 43 years old, me 47 years and feeling very tired. I get your point

 

[tod4]

Still not fixed
I've got a new motorised valve, and now have had a new pump fitted. There seems to be no air in any of the rads. I bled them and its only water that comes out. There is a bleed valve at the top of the system just past the motorised valve only water comes out of that as well. There were few bubbles at first but they only lasted maybe thre seconds.
The plumber has put flushing fluid in the system to clear any sludge. He also fitted new rad valves.
Now the nearest rad to the pump upstairs gets very hot. The next nearest is luke warm but then goes cold again and then warm etc.
The downstairs rads aren't even warm and the pipe to the third nearest to the pump is getting slightly warm and then cold again. The furthest is stone cold.
My original pump was on the slowest setting, I've put the new one on the middle setting. There seems to be a lot of bubbling noises.
HELP!
What else can be wrong?

 

[namsag]

What boiler do you have.

Also do you have an air seperator fitted ,this will be on the flow pipe between boiler and the pump (looks like a little cylinder with upto 4 pipes coming and going from it). These are a bloody nuisance for blocking and only allowing a little bit of water through and gives symptons you have

 

[tod4]

I'll have to check what make of boiler I have when I get home. But I don't have an air seperator unit. Last night I ran the system for about 5 hours, the bubbling noises stopped and most of the time the new pump sounded OK. A few clicks and whirs but nothing too bad.
I turned off the rads upstairs as they got hot. The down stairs ones got luke warm. This morning I turned the system on again for about 15 mins. and the pipes to the rads started getting warm. I checked for air again and still get water.
Could the downstairs rads be so sludged up they are blocking the system? If so will the flushing addative clear them or should I spend out and get new rads?

 

[muggles]

It could be that your pipes, rather than your rads, are sludged, in which case replacing the rads will do very little. Putting system cleaner in is all very well but it's not the most effective way of clearing your system, a full powerflush would be the way to go if sludge is the problem.

 

[tod4]

Latest. I've been running the system each evening with the upstairs rads turned off (as they get hot). The downstairs one are gradually getting hotter so I guess the sludge is clearing.
The new pump works the new motorised valve doesn't see this //www.diynot.com/forums/viewtopic.php?t=149859
So now I've got to try and track down an electircal problem
I no power at the valve, none at the box where the valve wiring connects but the timer seems to work so it's that Siemens unit (what ever that is).
Ideas and suggestions as always are very welcome, and calling another plumber or electrician isn't an option as I'm skint. But as an engineer as I should be able to fix it I just need to know what I should be doing.