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Autopapyrus · Renault Trafic III 2.0 dCi M9R (2020)
https://autopapyrus.com/guides/renault/trafic/replacing-the-inline-pre-start-coolant-heater/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Renault Trafic III 2.0 dCi M9R (2020): Replacing the Inline Pre-Start Coolant Heater

On the Trafic III with the M9R, the heater is usually installed in one of the coolant hoses (most often the supply or return hose of the small circuit, closer to the engine block or the heater core) and is powered from a mains outlet (220 V). Replacement involves draining some of the coolant, reinstalling the unit with new clamps, connecting power, and thoroughly bleeding the air from the system. The exact layout depends on how and by whom the heater was installed, so trace its position and the hose routing before starting work.

Difficulty: Medium Time: 1-2 hours Steps: 15 Tools: Socket and wrench set 8-13 mm, hose clamp screwdriver, spring clamp pliers, drain pan for coolant (at least 5-6 L (5.3-6.3 qt)), funnel, rags, multimeter, tweezers or cutters for zip ties, quick-release fitting disconnect tool if needed

Part

  • 🔩 Inline electric coolant heater (typically 1-2 kW, 220 V supply) with a mounting kit: hose connectors or adapters for the hose diameter, new clamps, and a new power cable with plug if needed. Coolant of the same type already in the system, for topping off. If the heater was installed as an aftermarket accessory, get a model with the same power rating and the same connection diameters
There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Haynes and 2 more. See manuals →

Step by step

15 steps
  1. Let the engine cool completely (at least 2-3 hours). Disconnect the heater's power cable from the outlet and from the vehicle. Disconnect the negative battery terminal.
  2. Locate the heater: it looks like a metal or plastic cylinder with two hose connections and an electrical connector, usually secured with a bracket or zip ties near the engine block or in the area of the headlights/radiator. If necessary, remove the lower engine splash shield and the decorative engine cover.
  3. Photograph the position of the unit, the flow direction arrow (if there is one on the housing), the hose routing, and the wiring layout. This will help you reassemble everything in the same order.
  4. Open the coolant reservoir cap (cold engine only) and place a drain pan under the lowest point of the radiator or the drain plug. Drain enough coolant so the level drops below the heater's mounting location. A full drain is usually not needed.
  5. Disconnect the electrical connector from the heater. If there is a built-in thermal fuse or temperature sensor, note how it is connected.
  6. Loosen the clamps on both hoses and pull the hoses off the unit, twisting them to break them free from the connections. Drain the remaining coolant from the unit and hoses into the pan.
  7. Remove the bracket or zip ties and take out the old heater. Inspect the hoses: if they are cracked, swollen, or hardened, replace those sections. Replace any extra clamps with new ones as well.
  8. Secure the new heater in the same location. Observe the flow direction (arrow on the housing) and the position of the connections: the unit must be oriented so air does not collect inside (outlet higher than the inlet, or mounted horizontally with the outlet facing up).
  9. Push the hoses onto the connections all the way and tighten the new clamps evenly, without overtightening. The tightening torque for plastic and thin-walled connections is low; the goal is a leak-free seal without deforming the part. The hoses must not be twisted and must not touch the exhaust manifold, the belt, or moving parts.
  10. Connect the electrical connector and the power cable so they do not touch hot components, and secure them with zip ties. Reconnect the negative battery terminal.
  11. Top off the coolant to the MAX level through the reservoir. Start the engine and let it idle for 2-3 minutes with the reservoir cap open, periodically raising the revs to 2000-2500 rpm. Turn the cabin heater to maximum to circulate coolant through the system.
  12. Gently squeeze the upper radiator hose several times and lightly squeeze the hoses near the heater to release air. Keep adding coolant until the level stops dropping, then close the cap.
  13. Warm the engine up until the thermostat opens. Make sure both radiator hoses are hot, the cabin heater blows hot air, and the connections near the heater are dry.
  14. After the engine cools, check the coolant level and top off if necessary. After 1-2 days of driving, inspect the clamp areas again for leaks.
  15. Test the heater: with the engine cold, plug in the power cable. After 10-15 minutes, the hoses near the unit should feel noticeably warm. If the unit does not heat, check the outlet, the fuse or circuit breaker in the line, the thermostat, and the connector. When testing 220 V with a multimeter, follow electrical safety rules.

Common mistakes and warnings

  • Work only on a cold engine: pressurized coolant causes burns. The heater runs on 220 V: disconnect the cable from the mains before any work, and when switching it on, check that the insulation and grounding are intact. Run the heater only when the system is completely filled, otherwise the heating element will overheat and fail. Air pockets in the M9R cooling system risk overheating the engine, so bleed the system thoroughly. If you have no experience connecting mains-powered equipment, leave the electrical part to an auto electrician.
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