Corrosion in Coolant reservoir

[mgcorreia]

I have a 97 Toyota 4runner 4cyl with 212k miles on it. I have only owned the car for about 7k miles. The first time I changed the oil, I noticed the corrosion in the coolant reservoir and did a good flush of the system and cleaned out the reservoir. I just changed the oil today again and noticed all the crud back in the coolant reservoir, a bunch of orange gunk. The reservoir is always nearly empty too. No matter how much coolant I pour in there it always goes nearly empty for some reason. I don't notice any leaks and my car runs fine, no overheating, and no codes. So I pretty much forgot about the issue after I did the first radiator flush. But I figure its probably time to look into this before it gets worse. I want to get it running tip top so I can drive it down to Baja mexico for surf trips. Any advice? thanks