What does the hose between radiator and turbo tank do?

[undertow]

Picked up an early gen 4 GT recently and on getting it home, found that someone has fitted a non-turbo radiator and blocked off the hose from the radiator to turbo tank.

After swearing and ordering a new correct radiator, I started wondering why this hose is needed. Coolant flows from the heads, through the turbo, into the tank, then back out the bottom of the tank to the water pump suction side.

I will replace the radiator with the proper one, but is this likely to have done anything bad? The turbo is original and still in good condition and the car's pretty decent overall with no other evidence of playing around.

[bigBADbenny]

The turbo coolant tank is the highest point in the GT cooling system. Similar to a swirl pot. That return hose likely equalises pressure in the cooling system. If you google cylinder 4 cooling mod extensively, you eventually find detailed diagrams of tgd cooling system flow path. So generally I’d say that return is for redundancy?

[Ric]

I would guess it enables passive turbo cooling by convection after the engine has stopped.
Without this, you may need to carefully let the engine cool down before turning off if you have been giving it a significant squirt immediately before stopping.

[Stifull]

Do that model engine have an engine cover nomally to direct airflow from the bonnet scoop and force the cool air through the intercooler or is there a boot around the inside of the scoop on the under side of the bonnet to control air flow...

[undertow]

The turbo coolant tank is the highest point in the GT cooling system. Similar to a swirl pot. That return hose likely equalises pressure in the cooling system. If you google cylinder 4 cooling mod extensively, you eventually find detailed diagrams of tgd cooling system flow path. So generally I’d say that return is for redundancy?

Thanks for the replies - I think I worked it out after reading the workshop manual. It's an air bleed from the radiator to the turbo tank. The cap on the radiator runs a higher pressure spring than the turbo tank cap, so rad cap should never lift under normal operation, and is basically just there to plug a hole. Any air in the top of the radiator will therefore tend to get stuck there without the rad-to-turbo-tank line. In practice it worked fine, but for the sake of $120 I've dropped in the correct radiator.

Thankfully car's completely stock with no playing around otherwise - makes a fun little daily runabout