Vintage steam engine Gabriel is being taken out of service for maintenance for several weeks from July 29.
However, regular train trips - four a day on Fridays, Saturdays and Sundays - will continue with a diesel locomotive, as will any booked excursions.
Bay of Islands Vintage Railway Trust spokesman Frank Leadley said work was needed on Gabriel's bearings and water tanks, while the boiler needed a general check-over and a full boiler certificate.
That required removal of the cab, tanks and cladding from the outside of the boiler as well as a general tidy-up.
Mr Leadley said the locomotive would be back to its full glory in time for summer.
Meanwhile, work was almost complete on another diesel engine, Timmy.
Volunteers had carried out restoration work on the donated engine, which, finances permitting, would be brought into service within weeks.
The vintage railway is still looking for volunteers for restoration work as well as drivers, firemen and guards. Call operations manager Matt Peers on 021 171 2697.