Removed radiator - now boiler will not fire

[SavageW]

From where your cold feed enters to the garage,then pump and boiler is this a long horizontal run of pipe work to the boiler? Any air vents/thumb vents if so on this run? Definately just sounds like an airlock which can be stubborn as f@£k sometimes.Try running the system an slightly cracking one of the pump valve unions to the pump with a bucket or rubble sack to see if you can clear air from the pump/pipe work this way
Also remove the pump head (pump valves isolated) an check the impellers, if half full of sludge use pin or pair tweezers to rod through every impeller to make sure it’s clear an the pump is actually circulating

 

[mache]

You might just have a system that is a pig to bleed, mine is and takes a while to shift airlocks. To get mine moving I need to fire in short busts, sometimes literally seconds and can hear a slug of water move in the pipe. Switch off, let it settle and hear the next lot of air bubble through, then same again. It does work and once done is fine and just bleed in the normal way.
Might be worth you trying something similar

 

[Rodders]

Hi all, just a quick update.

Replaced pump - the old one was full of sludge and red rusty water. Initially the boiler fired but then as before the pipe feeding the boiler got hot and the boiler shut down. I then fired up the central heating system and it gave out a massive gurgle followed by the sound of rushing water. The rads stayed on all evening and all got very hot.

Only problem was when I turned off and tried the HW on its own, boiler lasts 5 minutes and shuts down again. I assume I have a blocked exit pipe between the boiler and the tank? Otherwise I cant understand why the water wouldn't be pushing trough the boiler.

Thank you all for all your help...definitely getting warmer!!

 

[JCplumb]

Sounds like it.
If you can get a strong magnet on the pipework where the cold water from the loft tank is teed into the main heating pipes, you'll probably find that the magnet is attracted to the pipe.
It's an indication of ferrous deposits in the pipework and a likely blockage.
Also check the pipe that will tee off near your zone valve and then goes into the cylinder, that's probably blocked up.
Best fix is to cut out and repipe imo.
On the bright side, you're on the way to sorting this out. 🙂

 

[Rodders]

Just to add a little more to the puzzle...

When fired up together, we do get hot water, albeit heating up very slowly - would this mean that there is no blockage? The pipe leaving the boiler and entering the cylinder (mid level) goes through a gate valve and a 2 port valve (set to auto). These all get red hot when the CH is on, as does the pipe that tees off before the 2 port valve and appears to rejoin the pipe that leaves the cylinder on its way to the boiler.

Is it possible to have air in the cylinder that would prevent the hot water entering the cylinder (after the 2 port valve)? Only weird thing is that we are able to draw cold water out of the cylinder, which suggests its full!!

I know I'm going to get a plumber out and he fixes it in 2 mins and charges me £200!!

 

[Ric2013]

Sorry for lack of detail and inability to think, as very tired. But...

Cylinder almost certainly indirect (google 'indirect cylinder diagram') so the fact that you are drawing water does not prove there isn't air in the coil.

And I don't think a plumber will fix it in 10 minutes if it is a blockage.

 

[Rodders]

So the 'hot return from the boiler' is red hot, so I'm happy the boiler is working. This pipe is hot right up to the point of entering the cylinder.

Is it possible that air in the coil will prevent hot water entering the cylinder (and therefore returning to the boiler), and the hot water is backing up and running down the bypass valve which goes back to the boiler. So all the boiler is doing is circulating the same piping hot water (and eventually shutting off).

So final question; how the heck do you get air out of the coil? Was thinking of unscrewing the hot water feed into the cylinder, to hopefully let out air and no doubt a little bit of water?

 

[Rodders]

So I just fired up the HW. The hot return from boiler got piping hot instantly, right up to entering the cylinder. The bypass going back to the boiler got instantly hot, suggesting hot water was going back to the boiler and the pipe exiting the cylinder (going back to the boiler) got pretty hot pretty quick.

Surely that must mean HW is flowing through the coil?

 

[Ric2013]

Assuming the hot water going to the coil is pumped uphill, there could be some air in the coil which would tend to settle to the top, but because the system is pumped, water could still be entering the coil and going down by gravity, fighting the air running back up on the way. Loosening the nut at the entry to the coil as you have suggested might just work. I'd be surprised if the coil itself were blocked.

Sometimes there is a 'balance' gate valve on the pipework to or from the coil that may be mostly shut, but could now be blocked with gunk that shifted during the draindown? If so, may be worth opening fully and letting some flow through before putting back to how it was.