Rein CHE0573 (17127618510 equivalent) coolant crossover hose.
Rein CHE0573 (17127618510 equivalent) crossover coolant hose for E8x 1 series and E9x 3 series models with N52 or N52K engines.
Runs from expansion tank to top radiator hose.
Replacement every 4-5 years is recommended to avoid breakdown requiring tow. Top radiator hose replacement recommended in conjunction as the barbed fitting for this hose is known to rot internally, breaking upon removal of old hose. If the top radiator hose plastic fittings are maroon/brown, failure is imminent.