Soon as I poor water in to the overflow canister it runs out at the back of the engine near the firewall.
Where can I find a diagram showing the coolant lines on the back of the engine? on 1999 Volvo V70 XC
You have two hoses that attach to the firewall, these go to your heater, and it's likely where the leak is coming from. Best to have a VOlov tech address these, the hoses and especially the connectors are real finicky and if not replaced properly, will continue to leak.