81125136001 Fuel Flow Heater

Coolant-based fuel flow heater for MAN TGL, TGM, TGS, and TGX trucks (2005–2021). Mounted in the fuel supply line upstream of the main fuel filter, this unit transfers heat from the engine cooling circuit into the diesel fuel stream, preventing wax crystal formation and filter face-blocking that occurs when untreated winter diesel gels below approximately -5°C. The mechanism relies entirely on engine coolant circulation — no electrical heating element, thermostat, or control wiring is needed — which makes it simpler, more reliable, and lower-maintenance than electrically-heated alternatives. The unit becomes active automatically as soon as coolant begins circulating at start-up and provides continuous protection throughout cold-weather operation. Manufactured in Italy to MAN OEM specifications. Replace during any fuel system overhaul, when cold-start performance deteriorates despite correct fuel specification, or when external seepage from the coolant or fuel connections is detected. When fitting, replace both the inlet and outlet sealing washers and verify all connections are fully torqued before the first start. Compatible with standard diesel, low-sulphur diesel, and diesel-biodiesel blends up to B7.