Central heating problems! sludge?

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I am having problems with my central heating system which is a boiler/ hot water tank type.

1. The downstairs rads are all ice cold except for the top third and bits at the side that are warmish
2. The system gurgles and rattles.
3. The boiler cuts out (reset switch pops out) after about a minute of use
4. Before it cuts out the hot water tank and pipes rattle like mad and it feels like something's going to blow up. Theres also a loud knocking in the boiler sometimes before it cuts out.
5. Both hot water and heating cause these effects

From what I have read this sounds like rust floating about in the system clogging everything up. I have drained the rads and it was pitch black liquid. System is about 15 years old.

Is it too late to be able to clear it out with a drop of chemicals. Does it need a whole 'powerflush'?

[Lobster]

The whole thing definitely sounds like a severe case of sludge build up. You can only hope that if you get it de-sludged by whatever means, that there isn't permananent damage to the system. Presumably there was no inhibitor in the system?

Sounds like a lot of crud to get rid of by pouring in cleanser (but you have to flush that out anyway.) I've never gone in for powerflushing myself - AFAICR it's been panned on here as being very expensive, but it may be the way forward here?

If not, I'd drain down the whole system, remove the radiators one-by-one and take them outside to flush through backwards with a hosepipe. Very messy... Having shifted the bulk of it, then would probably be a good time to add a cleanser, following the instructions. And when you're all done - add a decent INHIBITOR!

David

[John Rumm]

It sounds like you have a serious sludge problem among other things.

However is also sounds like you pump has failed (probably related to the first issue), and the noise you can hear is water boiling in the boiler before it trips on its internal over temperature interlock.

You should be able to verify this by removing the small screw cover in the centre of the face of the pump (it will seep water a bit so have a cloth handy). This will expose the shaft with a screwdriver slot in it. Hence you can see if it is turning. If not you may be able to free it by manually turning the shaft with a screwdriver.

You can do it by taking off each rad and hosing it through. Google this group for advice on how - it comes up quite often.

Once the system is cleaned you need to ensure it is adequately dosed with inhibitor to prevent future repeats of this problem.

[TheScullster]

"John Rumm" wrote

Also check that water is not being pumped over via the vent back into the header tank (assuming this is an open system). This re-aerates the water and causes the sludge to return big-style.

Phil

[Martin Pentreath]

Investigate Fernox DS-40 - particularly agressive desludging chemical.

[Ed Sirett]

Thsi is going to require treating the severe symptoms, fixing the pump and/or the blockage problems and then most importantly fixing the underlying cause of the sludge. This much sludge requires a serious fault in the pipework layout.

All in all you might get the system back by diy and a lot of work but it will require a longer term solution as well.

[<me9]

And make sure there is no pumping over -- which could be the cause, or convert to a sealed system.

[John Stumbles]

Sounds like your pump's packed up and the system is attempting to work on gravity circulation alone.

All pitch black or the bit at the bottom? The latter is not abnormal though not desirable either and sounds as if the system could do with a cleanout. I'd stick a bottle of X400 or similar in when replacing the pump and let that run for a few days or weeks, then flush out and refitt with some X100.

However my bet is on the pump being the main problem.