Is there a way to pan a track to the left or right?  When I pan hard to left I still hear sound coming from the right monitor.
 
For example, when I start panning to the left I'd like to hear less and less of the signal in the right monitor.
 
Is this doable with SONAR Platinum 2016.11?

In a stereo track, the panner works like a balance control. Try using the Channel Tools plug-in.

Adding to Scooks note.
What is it your're trying to do:
1) pan a stereo track moving the whole material more to one side,(use Channel Tools) or
2) pan a stereo track getting rid of the other side, balancing (plain panning should do), or
3) pan a mono track to position it on the stereo field (plain pan).(EDIT: Missread the title. I see it's stereo panning you talk about)
 
"For example, when I start panning to the left I'd like to hear less and less of the signal in the right monitor."
 
What is actually happening? Your description leaves it unclear whether the panning has any effect at all, or if you're talking about some "leftover" audio audible on the quiet side. 
Are any FX involved?
 

you guys just made me think of something, rather than waste resources/cpu on a plug in,
cant you simply use the interleave button to set it to mono and pan it R or L ?
Because in the past, I've done what both of you have suggested.

Yes, that'll work. However, there is a risk that folding a stereo track to mono could result in some phase cancellation, especially with synths that are using chorus-type effects to make wide-sounding patches. If that happens, it may be better to convert to split mono and simply discard one channel.
 
This may be irrelevant to the original post, though. All stereo-panning subtleties aside, if you "pan" a stereo track hard left, there should be no sound in the right channel. Something is amiss, probably with a plugin or routing.

Several months ago, I had this exact problem. Troubleshooting revealed that the pan controls in my audio interface applet were not set correctly. Check your meters in Sonar - when you pan hard left, do the meters show anything on the right channel? If not, then it could be your audio interface pan controls.
 

Check the 'offset mode' to make sure there isn't anything there that could affect the pan too.

Thanks to all of you.  I believe GuitarGuy is on to something.  I pulled up another project and it works fine.  The problematic project I believe has the issue he mentioned.
 
Again, Thanks to all of you!

If two projects behave differently, then it's probably not the interface's mixer. I'd go with SuperG's recommendation  to check for panning in Offset Mode - the button labled 'I' in this image:
 
Hmmm... linked image looked right in preview, but not after submitting. It's the button to the left of 'R!'
 
If it's panned right in Offset mode, you won't be able to pan hard left in the normal Envelope mode. Envelope mode settings 'ride on top of' Offset's so to speak.