95 jeep yj heat problem

[Joe-d Baxter]

Hi I got a 95 yj that we did a 4.0 swap instead of the 2.5 and it runs great except when I take it down the interstate and if I drive like a hour or so when I go and stop it won't start back up if you let it cool it will start and go. What could be the problem? It's got a new thermostat and the gauge is reading normal like it's not registered like overheating.

 

[IGOTAJEEP]

[MENTION=806]Joe-d Baxter[/MENTION] did you replace the temp sending unit yet?

 

[Joe-d Baxter]

No where is that at and what's it do?