MongoDB 3.6 - Journal files are not getting cleaned up and they keep building everyday and use up a lot of disk space
This is a known issue recently discovered in the MongoDB 3.6.3 release when using WiredTiger on Windows: SERVER-33982: Unbounded growth of pre-allocated log files.

This issue will be corrected in the 3.6.4 production release, so upgrading to MongoDB 3.6.4 (or newer) when available should resolve the issue.

In the interim, possible workarounds are:


Disable WiredTiger preallocation in 3.6.3


In your MongoDB config file:

storage:
  wiredTiger:
    engineConfig:
      configString: log=(prealloc=false)

Or, via command-line parameter:

--wiredTigerEngineConfigString=log=(prealloc=false)


Downgrade to MongoDB 3.6.2
Restart your mongod to free up the preallocated space