This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Wow, you sure left out a LOT of important details!
1. How many requests are serviced before the system runs out of memory? One, dozens, hundreds, thousands?
2. What resources does the service use? ie: databases, external program calls? graphics contexts?
If this was my problem I would be using the tomcat Management application to monitor memory and Thread use change with time. The cause might just jump out at you from those statistics.