radiator problems

[wayfarer]

We live in a bungalow which was re-plumbed around 7 years ago, with new h/w cylinder, pipework to all rads,c/w tank, TRV valves and pump.The boiler and rads are 16 years old. All the rads are connected to pipes running through the loft and down the walls to them.
All has been fine until now. Firstly one of the lounge rads remains cold although the pipe to the lockshield valve is hot and eventually this bottom corner and top of the rad gets slightly warm. It seems to me that the hot water can get into the rad but not flow through as the TRV on the other side remains cold.I bled this rad but it stayed the same. I then removed it and flushed it through and a little black water came out but no sludge.
I checked tne TRV pin and this has movement up and down, so my first question is although the pin is free could the TRV still be faulty?
Now the bathroom rad doesn't get as hot as it has always done, and the other lounge rad seems to be playing up, sometimes hot, sometimes only warm.
My second question is could this be a pump/circulation problem? The pump feels like it is spinning and there are no odd noises coming from it, but it is as hot as the pipes it's connected to. The pump is a Wilo.
Any advice gratefully received.

 

[Simon F]

welcome along.

the pump could be on the way out.??
try giving the trv a few good taps it could still be stuck.??
there could be issues with balancing or blockages??
are there any bleed points in the loft?

 

[townfanjon]

As simon above says, pump is a definite posibility. Especially if nothing has been done recently .

 

[wayfarer]

I've tapped the TRV hard. Even though the pin is up could there still be a problem with it? As for the pump, it feels like it's spinning and is quiet, but could it be faulty and not working properly and should I just replace it anyway?

 

[townfanjon]

There is a way we "sort off " test pumps lol lol , I wouldnt want to tell you how to do it incase somthing happened , but no doubt sombody else on here will tell you how to do it.
Generaly on the TRV they are stiff to push down and then should pop back up smoothly but quickly , in my experience they are pretty damm reliable , far more reliable than pumps lol

 

[wayfarer]

Thanks for the replies so far, I will probably just change the pump and TRV unless someone has a eureka moment and recognises the problem!

 

[Frog67]

Has the system been drained recently?
Sounds like the system could be air locked.
You could go up into the loft and see if there are any air vents you could bleed.
Turn off any hot rads and see if that will push the heat into the cooler ones.
Its possible that the Cold feed is blocked and air is being pulled down the vent pipe.

 

[Last Plumber]

As above. Air lock sounds favourite. Especially as its a drop system

 

[SimonG]

Not tapped the trv hard enough. Change any cold rads trv's first before you fettle the pump.

 

[wayfarer]

Thanks all, I'll start with a look in the loft tomorrow then on to the trv's.

 

[BobbityBob]

I've had a similar problem with a radiator, TRV looked like it operated, pin worked under spring tension. Smacked it, swore at it, but it was blocked. If your considering changing the pump as well definitely a good time to drain down and replace.

 

[wayfarer]

I've had a similar problem with a radiator, TRV looked like it operated, pin worked under spring tension. Smacked it, swore at it, but it was blocked. If your considering changing the pump as well definitely a good time to drain down and replace.

Well I bled the rads again, bled the pump (no air released from either), checked the expansion tank ball cock and still had the problem.Then I increased the pump speed from 1 to 2 and there was a slight improvment although the corner of the rad near the TRV was still cool.
I have just changed the TRV and the problem is solved, all parts of the radiator are hot!
When I checked the old TRV, pushing the pin in and out was opening and closing the valve so there must be another problem with it. As said above, a properly operating pin does not necessarily mean the TRV is ok.
Thanks again for all the advice on this.

 

[wayfarer]

All was well for a few days but now the bathroom rad is playing up! With the other rads on it only gets hot around the inlet but if I turn the others off it will heat up.
All the rads are hotter since I increased the pump speed to 2 and I can feel the pump running if I hold it, and it is silent, but could it still be faulty?
As said before I live in a bungalow.
Thanks for your help.

 

[Last Plumber]

As I said earlier. It sounds like an air lock. You need to pull it through.
Hose on rad shut one side and run to drain until open valve is hot then swap valves and run other until hot. Start on farthest rad. It may sort all. If not you'll have to do them independently