I'm curious, is yours scraped up too?

Depending on how badly it's scraped, you may not be getting full seal on the radiator. Since the stock cap is too wide, it's trying to seal metal to metal. The inner spring pushes the inner seal against that lip, and that's what gives it 1.3bar (or 1.1 or whatever stock cap is) pressurization in your coolant system. It's probably not that big a deal as long as it provides some seal, else it's just always going to release pressure to the expansion tank.

At worst, you may have tiny little metal particles floating around in your cooling system.

 

I haven't looked inside to see if it's all scraped up. I just put in the koyo threw my old stock cap on and started driving.

 

I stopped by the local Pep Boys and asked them for a radiator cap that fits the Evo. Stant 10333 fits and has a skinny center metal valve. I installed it and will take the car out for a drive tomorrow to see if that fixes the coolant smell, hopefully it works.

 

any update here.? I'm having a similar issue.

 

Sorry for the long delay, I don't browse these forums that often.

The new cap is working pretty well, it fits properly and seals well, no more coolant smell around the radiator cap.