hello i have a 1989 civic si and just like the title says there is a small hole in my radiator cap. it is a very small hole, just big enough to let the tip of a pin through. its located near the very center of the cap. The cap does not leak coolant. so can i still use this cap or will it allow air into my cooling system. any help is appreciated

 

I would replace the cap ASAP. It may not leak coolant now, but it likely will. The coolant system is pressurized and vital to safe engine operating. For as cheap as a new cap is, I wouldn't risk it.

Good luck.