Wireless sensor network (WSN) technology presents significant advantages in the Internet of Things (IoT). WSNs are designed to operate in unattended, harsh, and complex environments. However, WSNs are resource-constrained. Due to the operating environment settings, there exist great challenges in the privacy and reliability of WSN communications. To achieve secure and reliable WSN communications, it is necessary to design reliable routing protocols and provide a method to evaluate the performance of the protocols. To guarantee location privacy of source nodes, numerous source location privacy (SLP) routing protocols have been presented in the literature. However, the SLP reliability of the protocols has not been evaluated. In this article, we achieve three main objectives. First, a new relay ring routing (ReRR) protocol is proposed to address some limitations of two fake packet-based SLP routing protocols. The routing algorithm of ReRR is specifically designed to provide long-term SLP protection. Second, unlike previous articles that focus solely on measuring the magnitude of the SLP protection using performance metrics such as safety period, capture ratio, attack success rate, and capture probability, this article proposes a novel approach to measure the SLP reliability of the protocols. In the third objective, we conduct a series of experiments to analyze the performance of ReRR and the fake packet-based protocols. Using the proposed approach, the SLP reliability of the protocols is evaluated. Experiment results reveal that the proposed ReRR protocol exhibits conducive performance features. It is observed that the fake packet-based routing protocols achieve strong SLP protection by integrating multiple routing techniques such as packet flooding and random distribution of fake packet traffic. However, the achieved SLP protection is short-term and less reliable. On the other hand, the proposed ReRR protocol employs an energy-efficient routing algorithm to guarantee reliability and long-term SLP protection. In addition, it is shown that the ReRR protocol guarantees improved network lifetime.