My current set-up is the one attached below (not mine), with 15 Heat Exchangers and 15 Stirling Engines, outputting somewhere around 600-680 EU/t and 260.000 hU/t. It is attached via Glass Fibre wires directly to my energy storage and my Molecular Transformer. Apart from one almost-meltdown, this set-up has been almost completely stable and self-healing, with it getting as much cool coolant in as hot coolant out through the Heat Exchangers and Stirling Engine combo.
However, when I redirected my wires back directly to my energy storage, I quickly found that all my coolant had turned hot and my reactor almost had a meltdown. As well as this most recent encounter and the previous one, I do not know what happened and what flaws are in the reactor.
Diagnosis, anyone? Also, any effective way of turning all the hot coolant back to cool coolant and back into the reactor? The Heat Exchangers are full to the brim with hot coolant.
I can't tell from the image, but maybe your energy storage is full? That will cause the stirling generators to stop production, the heat exchangers to stop exchanging, and the hot coolant to build up in the reactor. When the reactor's hot coolant tank is full, it will stop outputting HU and start building up core heat. If this is what happened to you, the simplest answer might be to connect some empty energy storage so the stirling generators (and heat exchangers etc.) can start outputting again.
Or funnel excess power to a mass/matter fabricator.
Reactors suck in the current version.
You should detect when something is wrong and have an auto-shutdown.
Luckily a fluid reactor generally won't explode. (It may instantly explode upon reassembly if you don't add plating, however)
I think we would need to see your coolant cycle setup?
All the reactor is supposed to do is to heat up coolant, after all.