LMSC Yes, I strongly suspect the pressurestat has ruptured, easy fix, just replace it. It was why I asked if it did it when the pump was running, it was the first thing I suspected. Check but I think you will find it’s leaking from the body and not the joint underneath.
Unscrew and then replace after using PTFE tape on the threads….job should take a few minutes and I think you probably have that spare.
After doing that, check the expansion valve just behind the pressurestat in the photo…screw the adjuster all the way out, count the turns…then screw it back in 1.5 to 2 turns max. Assuming it took more than 2 turns to remove it. This will ensure the pressure the valve can allow to build is kept as low as possible.
P.S. No other damage should have been caused, just make sure things are reasonably dry in there….because the electronics bay is separate, it’s all good.
Pull a shot with the lid off and check that during pump run, no water is coming from the expansion valve tube, you should be able to see in the drip tray as well. Water will come from there of course due to normal water expansion on heating from the boiler.
