My coolant res always leaks while driving under high heat conditions I replaced the cap but it has not solved the problem

 

I had some coolant spray around the engine bay which turned out to be a cracked radiator just below the cap. It was not easy to see the crack without looking very closely. I drove it like that for 4 or 5 months but the coolant level went down very little over that time - just a spotted engine bay every time I drove it. Bought a Koyorad from Moddiction with an upgraded fan switch and was able to replace it myself - I'm not much of a mechanic. The OEM cap didn't fit the Koyorad so if you go that route, make sure to get a new cap with the radiator.