Running Hot

There is no pressure in the system when it is hot. I used a Gates thermostat and rad cap that I suppose could be defective. There are no leaks.I say it runs hot because the gauge climbs above 3/4 mark and will over flow out the hose on the side of the neck. I am not using an over flow tank. I am going to borrow a laser thermal gun ( I think thats what you call it ) and check it to see exactly how hot it runs. Thanks to everyone. Bobby