Coolant Issues

Recently I have noticed that the temp of my car has been going up to 260-270 when idling or city driving, it will go down to 200 when on the highway. I noticed over the last month that the coolant in radiator keeps going low (which I am guessing why the temp is going up). I tried runing the car and checking underneath and pressure test but no luck. I just rebuilt the top end of the engine about 7 months ago (so new gaskets on top) but left stock cam in, put new radiator in about a year ago with new hoses and clamps, so I am guessing it is either the water pump gasket or timing cover gasket. I figured since I will be taking the pump off just going ahead and replace it. I wanting to get some opinions on some. Also if the may be a better way to test for a leak so I can save myself some time.

Thanks for the help.
 
Had a similar thing happen to me it ended up being the timing cover gasket leaking at the block. I could smell it but could not find any on the ground until it got really bad. That was a fun sat afternoon job to do. Also check your pass floor board could be the heater core, coolant runs through those all the time.

GOOD LUCK
 
Any brand of timing chain better than the other, I figure I will bit the bullet and change it. My oil pan gasket is leaking a little and it has been at least 5 years, according to the guy I bought it from, since they were changed.