Oil fired heating. the rads are working on ground level but stone cold upstairs were ok last week, tried on sunday and noticed problem. system 7 years old. Thermostat upstirs is showing on , but rads not heating at all.

low coolant level(rad fluid )will cause all these symptoms.make sure car is tottaly cold before checkin rad fluid!

is resurculating pump running ? cold rads maybe air loicked try bleeding off water at each rad.

Make sure the air is bled from the upstairs rads.
[air = top of rad is cold & bottom hot]

If you need to balance the rads to maintain an even flow through all then :-
Turn off all rads [one valve fully open and the other closed] Get heat going and open each rad valve, in turn, about 1 or 2 turns. Start with upstairs. The position you need to get to is when the return pipe fron each rad is a few degrees below the flow pipe. Adjust each rad valve to get this effect a few times may be necessary

IT sounds like the pump if this a wet sytem the expaisin tank could be dry

balance the rads.
upstair radiators turn all valves off,heat will then divert downstairs,open valves upstairs 4 turns on locksheilds and number 4 on trvs if u have any.
then if that does not work get a combi or powerflush.
if u cant afford then drain a little from rads,get x300 sludge remover from plumb shop and put in header tank(not hot water tank).
then fill system up and repeat balancing.

www.jollygreenplumbingmachine.co.uk

depending on the piping configuration; Series loop or mono-flow, you might need bleed the system. If its a mono-flow you would have bleeders on the radiators. Bleed them only till you you have water coming from the bleeders. If its a series loop, you need to bleed them from the area of the circulator by the boiler. There is a urge system you need to use and see if you can get the information on how to do that. I would think that somene here as written a tip on how to purge a series loop hydronic system. Also check to see that you have somewhere in the 12-15 PSI on your system pressure.

This is a flow problem within the system and you have ruled out the two major problems already.
asuming the pump has been fitted in the correct way round and the pump isolation valves are open fully. have you tried closing down the radiator valves upstairs and forcing the flow around the downstairs circuit? also is there any zone valves on the circuit not opening.
Is it a conventional type system with a header tank ?

first check the pilot is alight, it sounds like it is cause you can hear the boiler click. that click is the gas vale solenoid trying to open, if there is 240-230volts at gas valve when you here the click and pilot is alight the gas valve is broken. if you test for voltage look on the gas valve and see if its 240 or 24v obviously if it 24 v check for 24 volts, let me know

One of two things, it is either leaking out somewhere, which you should be able to see puddles on the ground or while its running open the hood to see if its leaking out on your motor, hopefully its only a radiator hope or something, this is the cheapest fix. 2. It's burning out internally in your engine, if this is the case you should notice white smoke out of your tailpipe, bad news is if this is the case, its going to get pricey fast because that would indicate a bad head gasket or cracked head.

Since you have done a good job bleeding the system, I will suggest that the impeller on the pump is bad. Many times these will simply deteriorate in the volute causing the symptoms that you describe.

This looks like it is in the wrong forum. Try reposting this in the heating section of the FixYa web site to get more responses.