Coolant hoses are sealed with a rubber o-ring inside the connector. Any time the hose is removed or disconnected the o-ring should be replaced. The o-ring can shrink with heat and time or become damaged. It's common to have leaks when re-using the hose and o-ring.
Instead of replacing the entire hose we offer the correct size replacement o-ring for the upper radiator hose on E46 323i, 325i, 328i, and 330i. This is the small 22x16 o-ring for the small connector from the hose to the expansion tank. Remember to also order the large o-ring (see Related Items below).
These are made of Buna-N (Nitrile) rubber and are compatible with coolant, water, grease, hydraulic oil, and engine oil (not brake fluid). They are rated for temperatures of -40°F to 250°F.
BMW Fitments:
3 Series
E46 (99-05) > 323Ci
E46 (99-05) > 323i
E46 (99-05) > 325Ci
E46 (99-05) > 325i
E46 (99-05) > 325xi
E46 (99-05) > 328Ci
E46 (99-05) > 328i
E46 (99-05) > 330Ci
E46 (99-05) > 330i
E46 (99-05) > 330xi