Iarnród Éireann said 67 new train carriages costing €117m have to be repaired to meet their quality specification.
The carriages were purchased from CAF, a Spanish rail equipment manufacturer.
Some repair work was carried out in 2006 but the problem still exists.
An Iarnród Éireann spokesman said the trains are of a very high quality and are not dangerous for customer travel, but they want the trains to meet specific quality standards.
He also said the problem was only on the Dublin to Cork line.
He would not disclose how much the repairs are expected to cost.
Tender invitations looking for companies to fix the carriages have been issued.
Iarnród Éireann insists CAF will pay the bill.
