New Metros pulled again over air-con leaks
BBCMetro bosses are still trying to correct a fault that is causing water to pour into the carriages of the network's new trains.
Tyne and Wear Metro's Stadler-built fleet had to be pulled from use during June's heatwave when it emerged their air-conditioning units were leaking.
The problem has reared its head once again as temperatures climbed over recent days, with three trains taken out of use.
Operator Nexus and Stadler said that condensation from the trains' heating, ventilation and air-conditioning (HVAC) system was draining too slowly during long hours of running on hot days - causing it to then leak through the air vents.
Transport officials are still "testing solutions" to solve the issue for good, while contingencies including extra cleaning have been put in place in a bid to minimise disruption, according to the Local Democracy Reporting Service.
The promise of cool, comfortable journeys during hot weather has been touted as one of the main advantages of the new £362m fleet, compared to the outdated Metro trains which have been running since 1980.
It is the latest blow to the rollout, which saw new trains being removed from the Metro timetable for more than a week after one of their doors opened on the wrong side.
Half of the Stadler-built fleet is due to be in service by the end of this year, with all 46 trains due by the end of 2026.
In a joint statement, Nexus managing director Cathy Massarella and Stadler Switzerland CEO Lucius Gerig said they were working "as quickly as possible" to get the HVAC units fixed.
"The introduction of the new Metro fleet is the biggest and most complex project in the history of the Tyne and Wear Metro and the current phase is the most challenging of any fleet transition project," they said.
"This is why we are taking a careful and phased approach to fleet introduction to promptly address any arising issues."