Elderly central heating system - cold radiators

[SussexMan]

Hi, would appreciate some advice.

1960s 3 bed bungalow, Boiler is a Thorn Marathon 50C (1980s?). 9 radiators in the house plus 2 towel rails. Only the hall radiator (nearest the boiler) gets particularly hot, others get warm but have cold spots most notably towards the bottom of the radiator, sounds like classic sludge build up to me. We've been here 14 years and no flushing has taken place in this time, radiators are all possibly installed at the same time as the boiler, but I can't be sure of that. The two towel rails were fitted at the time we moved in.

So the question is, would there be value in replacing the radiators (full of sludge) which are possibly getting on for 40 years old? I appreciate there may be sludge in the rest of the system, but presumably new radiators are more efficient these days which may counteract some of the extra cost? The boiler itself seems to go on and on and I'm reluctant to change that being so simple and having a cast iron heat exchanger. Have a British Gas maintenance contract but I know they charge an arm and a leg for any other work.

Would welcome any advice! Thanks in advance.

 

[ShaunCorbs]

I would pull a rad off at a time and flush / connection a hose pipe to one end and flush it out for upto 5 mins and then swap the hose to the other connection

If it still looks bad you can tap the radiator when your flushing with a rubber mallet

 

[SussexMan]

Thanks for the reply Shaun, that sounds like a sound idea, but I can only image I'll make a mess taking the radiator off and drip gunge all over the carpets as I can't see that any of them are fitted with isolation valves. Much though the DIY route appeals to my wallet, I've not done much more plumbing wise than change over a few taps, change washers and a few other minor things.

 

[ShaunCorbs]

Best to get a heating engineer in then

 

[SussexMan]

Yep, will do. Was just hoping I might get some pointers first on whether the old radiators are worth keeping or if I may as well change them at the same time.

 

[ShaunCorbs]

That's upto you tbh

If there not leaking and look ok eg not painted black they should be fine

The only good point in regards to new ones is they will give slightly more heat out

 

[SussexMan]

The old ones are looking a little tired and one is quite rusty at the bottom and will definitely need replacing. Thanks for the advice.

 

[Frog67]

It does sound like a build up of sludge in the system. Cold spots and luke warm rads is a sign of its presence. Other things to consider are the controls in the system ie the pump and any zone valves. These are likely to be affected with sludge build up as well and would effect the efficiency.
I would consider cleaning the system before changing the rads as there will be sludge still present in other parts of the system such as the boiler, pump, pipework ect.

 

[SussexMan]

Thanks Frog67, that does sound logical.
Sounds like I'll be going for a flush then! Thanks.