I finished replacing all the hoses today but as I was clamping the last one to the firewall the clamp screw popped off and went hiding somewhere in the engine bay. Since it was raining on me and I had been standing in an awkward position for two hours I stormed off furiously, so TBC tomorrow.

I have been wondering what caused the leak and overheat, and noticed a few things:

The overflow canister is constantly empty. I used to fill it up between the 'low' and 'high' mark but the coolant disappears within hours.

Regarding the overheating: Could a faulty/blocked thermostat cause excessive pressure to build up in the system and eventually lead the heater/bypass hoses to leak? Would that show up on the thermometer? AND: Could a faulty water pump lead to the same issues?

I am still unsure why my system kept leaking and overheating, and I want to believe it has something to do with the overflow canister since the pressure should have pushed some coolant into it.

EDIT: Regarding torquing up head bolts, do I need to remove the rocker cover to get to those?