Brakes First Test Drive Did Not Go So Well, Having Some Issues.

Got the rear caliper on, bled the system and did all the other last min things that needed to be done. Took it out for a drive but the brakes are still messed up. The pedal is very stiff and when I press down on it it barley wants to stop. Also the temp went up to about 230. It never usually gets hot at all. I did not take it out of first gear I just took it out on the dirt road I live on but in the short distance I went the temp shot right up. I got it back home and put it in the garage until I can figure out what's causing these issues. The thermostat is new and there is plenty of coolant in it. I do know that some of these thermostats are bad out of the package but what other issues could be causing it and what about the brakes being stiff and not wanting to stop all that well?

I forget to burp the cooling system so I know thats why its over heating. I'll do it tonight when I get home. Was in such a hurry to drive it I forgot all about it.

I did not check the VAC to the booster, how do I do that?

Oh and to add insult to injury I did not need a rear caliper. There is small washer/fitting that goes with the banjo bolt. Thats why it was leaking. Well anyway it has new rebuilt caliper on the rear passenger side.

ok I'll check that tonight as well while Im burping the cooling system.