I have a 97 Honda Civic which I just purchased used about a month ago.

The entire cooling system was changed out right before I purchased it. Radiator, Hoses, Radiator cap, Thermostat.

The issue im having is that the car will overheat when im idle. Once i start driving the car will go back to normal temp.

I have noticed that when it does this, I just need to top off the car with coolant and im good for a few more days.

I had my mechanic check it out, the fans work, and he did a pressure test on the system, and it didnt show any leaks.

Anyone have any idea/solution for this?

 

You are losing coolant. The key question that must be answered is whether you have a leak or are burning coolant in the cylinders?

 

how do I check to see if its leaking or burning the coolant?

 

Did you see white smoke coming from the tail pipe?

Refill cooling system and let engine idle while you look for coolant dripping from the radiator, hoses, or engine. Having the front end on stands may help. Also watch for white smoke in the exhaust.