Coarrays have been part of the Fortran standard since Fortran 2008 and provide a syntactic extension of Fortran to support parallel programming, often called Coarray Fortran (CAF). Although MPI is the de facto standard for parallel programs running on distributed memory systems and little scientific software is written in CAF, many scientific applications could benefit from the use of CAF. We present the migration from MPI to CAF of the libraries PSBLAS and MLD2P4 for the solution of large systems of equations using iterative methods and preconditioners. In this paper, we describe some investigations for implementing the necessary communication steps in PSBLAS and MLD2P4 and provide performance results obtained on linear systems arising from discretization of 2D and 3D PDEs.