Hi all. Last year I purchased a NOS plastic radiator that was sitting in the box for 30 years. It worked well at first but then developed a small leak. It looks as if the leak is coming from the useless cap on top of the drivers side. Can this cap be removed at all? Maybe a bead of silicone or a new gasket under the cap need to be replaced. It doesn't leak much and only noticed a small drip when the car is parked for a while after a run. Any info on this would be helpful.