Like BigE said - this is a very easy problem to remedy before it even becomes a problem. The Roe kit is simple and cheap. Do not drive it that way - it only takes a few drops to ignite your engine bay. Call Scharf or JonB - im sure they probably have one laying around they can sell cheap, if not they are 100x better than a stealership on inventory and price. They may even know of a good alternative if not. Also - "cranking it" tight is also a very bad idea. You risk cracking the plastic on both the reservoir and the cap AND it will eventually break loose again from heat cycling. The cap and reservoir are made from two different plastics and nothing you can to will prevent them from expanding at different speeds.