cold lower rads, scolding hot water

[diymunkee]

Hello there. We had a leak on the weekend, fairly major. One of the return valves off a radiator went kaput, water everywhere. Anyway, got new 'out' valve for it, sorted. Filled the rad back up and now the heating is up the spout. A couple of rads upstairs are working, and, after several hours, one of the lower rads gets slightly warmer ... but then the upper ones go cool again, like the hot water is taking turns in each radiator. The hot water, now, is absolutely boiling, like its never been before. Its a fairly old system, with baxi (Bermuda??) in the living room, whereby the boiler is behind a groovy gas fire. When this gets going, about every 20 minutes, you can hear the water boiling away, it goes for about 2 minutes, starts to calm down, and then there is a bubbling sound similar to that of a kettle coming to the boil. The pump still hums away, so that isnt cream crackered. We've drained the system, bled all the rads etc, and the pump, and the pipe where in the airing cupboard where the tank sits. Any ideas? Or is it time to call in an engineer?

 

[kevplumb]

check the feed tank in the loft

check the pump is running

 

[diymunkee]

Cheers kevplumb. Did that, ball float thing is fine, tank is 3/4 full (Below overflow pipe!). And it refilled after we drained, and filled up, the system.

 

[kevplumb]

pump

 

[diymunkee]

Well, the pump is running, and making the same noises as it was before the leak, but it does seem to be a little quieter ..... except for this morning, when we woke up it was hellish loud, so I went and turned it off, kicking the airing cupboard door behind me.

 

[kevplumb]

try bleeding it

 

[diymunkee]

Did that. When I bled it the first time, after refilling, bubbles came out, I let it bleed till no more. Have tried it a couple of times since only to get a trickle of dark/murky water.

 

[ChrisR]

Look for a bleed point near where the boiler pipes go into the HW cylinder.

 

[diymunkee]

kevplumb, you're a star. I got home last night, sledgehammer in hand, ready to unleash my fury on whatever I came into contact with first, and then a ray of light hit me. "Bleed the pump, Bleed the pump ....". Now, although I had already bled the pump, like I said, the day before, to no avail, but thought theres no harm in trying again. Sure enough, when I opened up the valve, more bubbles and murky water, mopped that up, let it run a bit more, then more bubbles .... I did this for about half an hour, got through half a roll of loo-roll mopping up (Its the only thing I had to hand!!), the bubbles eventually stopped, water turned clear, radiators blasting out the heat, sorted. Was so pleased. I guess I'll keep bleeding it for the next week or so, just to make sure. Anyway, thanks very much for your advice, much appreciated.