No reason to suspect the head, bypass the core as noted , watch oil and coolant levels to see if they change.

No reason to suspect the head, bypass the core as noted , watch oil and coolant levels to see if they change. ^^ seconded. It's a pressured coolant system so when the core does fail (and it always does) it's usually spectacular! I used that exact same heater hose jumper method on my car when it ble...

Volvo water pumps (like all water pumps I know) are centrifugal pumps. The faster they turn the more flow they make. With normal restrictions in the system, they will make more pressure at higher speed. Sooner or later, the weak point will leak at full engine speed.
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