BMW 540I 1999 — technical service bulletin
Bulletin B170100 · NHTSA communication 10244236 · issued Oct 16, 2023
Technical service bulletin
communication type
Engine and Engine Cooling
component
1999
model years
2
vehicle entries
Official summary
The lower radiator coolant return hose may come in contact with the secondary air system check valve flange gasket when the engine coolant is at operating temperature due to coolant system pressure and expansion of the hose.
Vehicles covered
What a TSB means. Technical service bulletins are repair guidance manufacturers send to dealers — they are not recalls, and repairs are not automatically free (warranty extensions are an exception worth checking). The full document is available via NHTSA’s vehicle lookup.