VW Jetta TDI heater hose. These hoses pass through the firewall and cycles the coolant through both HVAC and engine cooling system. You may find you need to replace the heater hose when you remove the heater core from your Jetta or it just happened to spring a leak on you.
These VW heater core hoses connect to the heater core shown below. When you remove the hose from your car inspect the plastic connection point that passes through the firewall. You don’t want this section to be cracked and leaking to your interior. You are going to lose some coolant when you replace the heater hose. Make sure you top off your Jetta TDI Volkswagen approved German Pentosin coolant.