In this paper we present an online algorithm that attacks the problem of placing relay nodes in regions where high localized congestion is detected. Congestion refers to the network overload caused by excess concurrent attempts of wireless devices to access the common shared channel. Our algorithm uses the Expected Transmission Delay (ETD) metric based on both current measurements and history observations over a window of time and is used by the nodes to identify the level of congestion in the local environment of the node. Our scheme uses a dissemination probing mechanism to exchange statistical local information periodically which are used to detect the congested area. Detailed simulation results illustrate the working and benefits of our approach.