Cooling system re-visit

After the GBS runout I had some overheating problems. My current thinking is it was primarily down to the cooling system finding a hot shortcut through the heater matrix rather than the radiator. I ran the whole weekend with the heater valve wide open, and once closed (and refilled with coolant) the car was behaving pretty much like it ever did.

Coolant checked with a CO2 detector kit and nothing showed up - so touch wood I have avoided a re-build and head gasket issue - but time will tell.

Today was just checking the coolant circuit for leaks by pressurising the system & refilling. 

My patent leak finder kit consisting an off-cut of pipe with self amalgamating tape to make a seal and a foot pump to add pressure:

The pressure cap opens around 20psi, so pressurised the system to the same point and listened/looked for leaks: (cap was on when testing)

Two leaks found - a couple of weeps from the heater take off points, needing a tweak with a spanner, and a major one from the filler cap seal. Taking care to avoid ingress of dirt with some masking tape: I sanded the top of the filler casting flat with a wood block wrapped in sandpaper, just enough to give a completely flat surface. Adjusted the cap by giving its tabs a little pinch with the pliers and cleaned up the rubber seals:

Progressed from barely holding any pressure to now stably holding 20psi which seems promising; admittedly its a cold test & only checks the external cap seal not the internal pressure spring, so there might be some more issues lurking and/or when everything is hot.

Double checked the overflow was connected correctly to the syphon by sucking on the free end and got a taste of rusty/slightly antifreeze water - so thats fine.

Maintenance

Refilled the car with at 50% antifreeze to water mix, ran it to temp and now waiting for it to completely cool down overnight before topping up again & hopefully getting rid of air locks. Best advice from Simon @ GBS is the coolant should sit level with the inside/pressure seal on the cap. time will tell if I can achieve that.

Then - realised I forgot to install the restriction valve in the heater lines - bother - I'll worry about that later.