Ideal classic RS40 not staying on burn.

[foxinthehouse]

Hi everybody, looking for suggestions to fix my Ideal Classic RS40. OK it's 29 years old, but this is the first time it has let me down, it is a simple boiler so I feel safe leaving it in the winter when I am not here. (Well, until now)
The problem.
We got home from a trip and the central heating was would not work at all. Really dreadfull noise from pump. New pump fitted, all good and the system started working normally. Nice warm house again. All good for a couple of days. Then we noticed the boiler was starting to take longer to heat the radiators. They were getting luke warm at best and finally no heat heat at all. The boiler lights OK, but the flames do seem a bit low power than I remember, then after a few minutes it stops burning even though the thermostat is calling for heat. The radiators are barely tepid, if at all. It may cycle again after a while but it will not stay on, nor will it roar away as it used too.
The circulation pump is new and showing 1 cubic metre per hr. The bypass valve is not open (just a bit). New 3 port valve, working, although we never use the hot water on gas. Our heating engineer bled the system, including the boiler when he changed the 3 port valve. He is not sure what the problem is but suggests the gas valve, although I am wondering whether it could be the control valve thermostat as it fails to start a burn if you turn it up. There is power to the control valve.
Any suggestions gratefully received.
Thanks for reading.

 

[ianmcd]

go to the highest radiator and open the bleed screw does water come out ? if not you have a blocked cold feed , very unlikely it is the boiler, one of the best ever made

 

[foxinthehouse]

ianmcd. - Thanks for the suggestion. All radiators bled and expressing water. The pump states it is circulating at 1.1cubic mtrs. There are no cold radiators, only luke warm at the bottom. It does appear that the boiler is cutting out after getting like warm. The flow pipe immediately out of the boiler is the same temperature as the furthest radiator.

 

[Terrywookfit]

Is the Multifunction control valve energised .

 

[foxinthehouse]

Just heard back from engineer that part is obsolete, so it is a new boiler. Shame, just a few months before its 30th birthday. Anyway, it is a good opportunity to upgrade to one that has electronic ignition. It is surprising how much the gas costs now just running the pilot light.
Thanks for everyone's help.

 

[ianmcd]

Just heard back from engineer that part is obsolete

Nothing on your boiler is obsolete , very easily repaired

 

[Terrywookfit]

He is NO fookin Engineer!!!

 

[foxinthehouse]

ianmcd. According to the Plumber/servicing chappie/ who has checked with suppliers, the gas valve is available but not the control thermostat.
It may be the case that parts are available somewhere, but let's face it, the RS40 was a very reliable boiler but discontinued in 1995 and is terribly inefficient compared to a modern boiler. I was in Portugal all of December/January and the gas bill with the heating off but frost stat on was £133 Dec, £109 Jan. My neighbour, same house, new boiler, didn't spend that much and they were at home with the heating on, not 1000 miles away. It is also possible that the boiler packed up sometime in January as Feb/March bills seem to be just pilot light and standing charges. Lucky the boiler didn't freeze.
So, all in all, I am happy to have a new boiler, just over 2k fitted next Monday.

 

[ianmcd]

All Ideal Classic use the same thermostat part no 137658

 

[ianmcd]

He is NO fookin Engineer!!!

and neither are you fookwit, he asked for advice and he got it no thanks to you Fookwit

 

[Terrywookfit]

and neither are you fookwit, he asked for advice and he got it no thanks to you Fookwit

Wind your neck in Ian .....I was referring to the bloke who could not fix it !!
I have never aspired to being an "Engineer". The only letters after my name have been C..nt **** Bast.. etc.
I am a mere Plumber / Gasfitter.

 

[fixitflav]

All Ideal Classic use the same thermostat part no 137658

Perhaps I'm missing something, but I can't see anything in that link that looks like a control-stat.
Got this from the boiler manual. No idea whether it's still available (if that's the problem)

 

[foxinthehouse]

ianmcd, that is interesting, and a bit disappointing. I am changing my Plumber as I am now not too happy with the one I use. He has been fine all these years for servicing, but, I think, out of his depth when it came to this problem. I kept trying to tell him it wasn't a circulation problem, but a problem with the boiler. £200 and 3.5 hours yesterday to change the 3 port valve (it actually failed about 10 years ago, but I never bothered as I don't use gas for hot water and it was stuck on heating. I told him it wasn't that anyway), and much head scratching. Came this morning with a quote of £2,900 for a replacement boiler, make not determined on the quote. I then got a quote, very detailed, from a highly respected installer locally for £1,800, with Worcester 18kw boiler. They also do a good service contract for £7 a month, so I will move my custom to them. Plus they can fit it Monday.
So thanks again for the advice, which, as always from you, was very helpful.
I'll just ignore the fookwit!

 

[Terrywookfit]

If you have voltage at the MFV the stat is not the problem.

 

[foxinthehouse]

fixitflav. Trouble is, I'm not even sure the problem is the control stat. Could be the gas valve or anything really, but definitely in the boiler. I could end up changing everything, including the drop down front panel which dropped off years ago! The burner is also showing its age with lots of rust, as it is mounted on a single skin outside wall in the garage, so moisture gets in all the time. Bottom of the boilercase looks like it's covered in gravy granules.
As I said to ianmcd, I am happy with my decision to change it after 29 years, but I wouldn't mind placing a bet that the new one will fail well before that!