MRC8378 - Land Rover Seal-duct blower-heater

Land Rover Defender Air‑Duct to Heater Blower Seal - MRC8378 (Heater Intake / Blower‑Duct Foam Seal, 90/110/130)

MRC8378 is the air‑duct sealing foam used on Land Rover Defender 90, 110 and 130 models, fitted between the heater blower housing and the fresh‑air duct to prevent air loss and ensure correct airflow into the heater unit. Used across Defender production from the late 1980s through the mid‑2000s, the seal sits at the interface where the intake duct meets the heater blower or fan case, forming a compression joint that stops heat loss and keeps the system operating at its intended efficiency.

Supplied in the characteristic dense black foam used on factory assemblies, MRC8378 follows Land Rover’s original profile for the duct aperture, with a cut pattern designed to compress evenly once installed. Genuine versions arrive in Land Rover‑marked packaging and retain the factory geometry required for a proper fit against the heater casing, blower outlet and bulkhead duct, preventing gaps that otherwise lead to cold‑air bleed or reduced heater performance.

Engineered for Defenders up to 2006 with the traditional heater box and external intake ducting, the seal’s purpose is both functional and protective: maintaining positive airflow through the heater core, reducing noise and vibration transfer, and helping shield the heater assembly from dust and moisture ingress drawn from the wing‑intake area. Vehicles that spend time off‑road or in wet climates often require renewal of this component, as the original foam can harden or crumble with age.

MRC8378 is a common replacement during heater‑box refurbishments, bulkhead restorations, and when the air intake system has been disturbed for wing repairs or blower‑motor replacement. Its correct fitment ensures that the Defender’s heater system continues to operate with the airflow and thermal performance intended when new, particularly important on cold‑climate vehicles and earlier 200Tdi/300Tdi models where cabin heating relies heavily on tight duct sealing.