Worcester Highflow 3.5 boiler problem

[pauliwallnuts]

Hi,
I was looking for advice on a boiler problem.
I have a Worcester Highflow 3.5 boiler with an open flue it is around about 15 years old and has been pretty reliable apart from a couple of Thermocouples and a new diverter valve.
Serviced every year by my cousin who is a heating engineer (trouble is he is on holiday for a fourtnight) hence the question raised here.
Yesterday evening we smelt burning coming from the boiler I shut it off and let it cool down overnight. After removing the cover today I find that the internal chamber and feed pipes to the heat exchanger compartment are all covered in black soot and the hotwater pipes were still warm.
It seems that everything has overheated.
I cleaned everything off and hoovered away all debris and now the pilot light will not stay lit either. Would this be a case of a faulty boiler limit thermostat? Or is there another explanation.
I am a Electronic engineer so can carry out most electrical tests quite easily.
Any help would be greatly received.

 

[tonybhoy]

Sounds like it has sooted up-incomplete combustion-you need to get someone to look at it and leave it off because it could be dangerous.

Pilot light staying off could be because of a blocked flue or there may be a flue stat on the boiler that has tripped due to high flue temps in the primary flue ensuring that boiler gas valve has been turned off.

Either way don't turn it back on.

 

[pauliwallnuts]

Thanks for that.
Will get someone to look at it ASAP.