Pilot light was going out every month or so, so the immediate assumption was the TC. However before changing this, I had a look at the spark electrode. After 30 years of it sitting in the pilot light a lot of it had corroded. It should loop over and present itself about 5mm from TC but mine didn't. Fitted a new electrode, which sits in the pilot, glows red hot and I guess that some of the IR radiated from it helps to heat the TC. So before rushing to change TC, check electrode. If you need to check TC, its output in gentle heat should be 15-20mV. Voltage to hold pilot valve open about 8-12mV, so lots of headroom.
Also, minor water leaks can be self sealing. about 12 years ago it started to weep along output manifold joint, but within a couple of months it must have rusted up, sealed itself and it has been bone dry since then. Isn't cast iron wonderful ?
Also, minor water leaks can be self sealing. about 12 years ago it started to weep along output manifold joint, but within a couple of months it must have rusted up, sealed itself and it has been bone dry since then. Isn't cast iron wonderful ?