Answer
Aug 04, 2025 - 04:11 PM
On the 2015 ML350, the heater core hoses are routed to the coolant circulation pump, which is mounted behind the front left fender liner. You’ll need to loosen and partially remove the front section of the liner to access the hose connections.
The two heater hoses run to the circulation pump (located near the firewall, driver's side), and they’re usually clamped in place. If you’ve already replaced the radiator, water pump, and thermostat but still aren’t getting heat, it's possible that:
- The heater core is airlocked and needs bleeding
- One or both of the hoses are kinked, blocked, or not properly connected
- The circulation pump itself isn’t functioning, or there's an electrical issue
Start by checking those hoses and fittings under the fender and verify coolant flow through the heater circuit. That’ll usually get you on the right track.
If you want the full procedure with illustrations, torque specs, and troubleshooting, it’s all covered in the OEM manual here 👉 2015 Mercedes-Benz ML350 (W166) Service & Repair Manual Software
