Make sure the lid is vented on the black canister.
Otherwise it is as if you put a 1000lb cap on your radiator.
Pull the small hose off the radiator and apply some air pressure (20 lbs) to the hose going into the black overflow canister.
If you can not presurise the canister your good
If you can presurise the canister you need a hole in the cap of the canister.
The way this works...
Fluid in your radiator expands when it gets hot. If your radiator is 100% full the expanding fluid starts to pressurize the cooling system. Once the pressure is over the rad cap rating (16 lbs?) the fluid starts going out the small hose to the recovery canister.
There is air in the recovery canister and if it is vented properly the air goes into the atmosphere as the fluid enters the canister.
IF the canister is not vented then as the fluid enters, the air inside gets compressed and builds pressure in the ENTIRE cooling system. Basically you plugged up that small hose at the rad cap.
The coolant will continue to expand and build pressure till something gives, like the radiator tubes or tanks, or hoses, or the canister, or freeze plugs, or gaskets. What ever is the weakest link in your cooling system.
The small hose entering at the bottom suggests that it is a cooling system recovery system rather than just a catch can should you overflow at the track
