Elring 278.386 Engine Coolant Bypass Line Seal Ring

Engine Coolant Bypass Line Seal Ring

Elring 278.386 is an engine coolant bypass line seal ring built as an FPM O-ring for precise sealing in cooling-system connections. With a 22 mm inner diameter, 26 mm outer diameter, and 2 mm thickness, it is sized for select BMW applications that require a reliable coolant seal.

Use this Elring 278.386 seal ring when servicing coolant bypass lines on BMW M3, M5, M6, X3, X5, Z3, and Z4 applications listed below.

Key Features

• Part number: 278.386
• FPM (fluoride rubber) construction for sealing performance in coolant-system environments
• O-ring shape with 22 mm inner diameter, 26 mm outer diameter, and 2 mm thickness
• Engine coolant bypass line seal ring for select BMW cooling-system service
• Cross-reference example: BMW 11 41 1 304 178

Detailed Description

This Elring coolant bypass line seal ring is a direct-fit sealing component for applications that call for a 22 x 26 x 2 mm O-ring profile. The FPM material is selected for use in engine cooling circuits where stable sealing around coolant passages is required. For BMW owners and technicians, 278.386 is a practical replacement for service work on models including BMW M3, BMW M5, BMW M6, BMW X3, BMW X5, BMW Z3, and BMW Z4, depending on the exact engine and connection point.

Part number 278.386 is also referenced in OE-style interchange listings, making it easier to match the correct seal during cooling-system repairs. If you are searching for an engine coolant bypass line seal ring for BMW M3 or BMW X5 service, verify the dimensions and application notes against the original part before installation.

Common Repair Uses

• Coolant seepage at a bypass line connection
• Sealing wear from heat cycling and age
• Leak repair after cooling-system service
• Replacement of a flattened, hardened, or damaged O-ring
• Restoring a proper seal at the coolant passage

Installation Notes and Tips

Confirm the inner diameter, outer diameter, and thickness before installation to ensure the seal ring matches the original component. Clean the sealing surfaces thoroughly, inspect the groove or mating surface for damage, and install the O-ring without twisting or nicking it. Use the vehicle service information for the exact coolant bypass line location on the applicable BMW M3, M5, M6, X3, X5, Z3, or Z4 model.

Quality Assurance

Elring is a recognized sealing-system brand, and this part is manufactured to support accurate fitment and dependable sealing in automotive cooling applications. Part number 278.386 is specified with clear dimensional data to help confirm the correct replacement before service.