Can Overheating Be Linked To Overflow Res

[scruffboy]

My overflow reservoir has a leak. I attempted to fix it on the weekend but it started to rain and I realized there was more than one bolt holding it on like I thought, so I figured it could wait till this weekend. I usually had to add coolant every two days but I ran out and for the past two days have been running with the overflow dry. Toyota wants 105 US dollars for this stupid little item and I'll be damned if I pay that for what amounts to a plastic soda bottle. Anyways, today I overheated after a short run (maybe two miles). I let it cool down and drove it back home slowly with the hood popped and the heater blowing. So I got home and sure enough I was low on coolant in the radiator (which has never happend before) but I saw no leaks. I filled the radiator and the res and ran the car a little and everything seemed to work fine and still I saw no leaks under the car. Can this little reservoir cause such a headache? I left the car in the driveway and took the bus, but I plan on taking it off and using some kind of epoxy on it. What I'd like to know is, should I be looking some where else for leaks, or can the reservoir be the totality of my problem? I love this car and it usually runs like new but I'm having some little thing drive me nuts every other week lately.

Thanks

James in NJ