<p>I have a homemade 3D printer running on ramps 1.4
When i start a new print and the hotend reaches melting point of PLA, the PLA start coming out of the hotend.<br>
This goes on for as long as the temperature is kept above melting point, without moving the extrusion gear.   </p>

<p>The extruder is a bowden type.<br>
Hotend is a J-head.<br>
I am currently using simplify if that makes any difference regarding configuration.</p>

<p>Any ideas what to do to prevent this from happening?</p>

Does it really go on for more than a minute or so?  You can't get filament from nowhere, so if the feed gear isn't moving, sooner or later all the material in the reservoir inside the nozzle & hotend will be melted and gone.  Leakage like this is normal, and probably a lot more noticeable if you have a larger diameter nozzle.
I would recommend checking to see if your gcode includes a large retraction at the end of the print.  That would reduce the pressure and the amount of material left inside the hotend.