Hi all, I've been having a problem with my cooling system. A few weeks ago I realized that my reservoir tank was empty, so I added some water to the max line. After another week or so I popped open the hood and noticed it was empty again, so I added water again. At this point I knew this shouldn't be happening. These past 2 weeks I noticed that when I pop open my hood, the water somehow leaks from the top of the reservoir tank. The reservoir cap is always wet and its surroundings are wet also.

On Tuesday I was driving and noticed some steam coming out of the passenger side of the hood. When I opened the hood the reservoir cap was wet and I'm assuming the coolant is coming out from the top. Later that day I opened the radiator and had to top it off with water, it took about 36oz or so to top it off. Plus I put more water in the reservoir. Friday, I drove around a lot and by the end of the night I noticed steam again coming out from the hood. I opened the hood and noticed the same thing, water all over the reservoir/cap and dripping down. I also noticed that the water in my reservoir was bubbling/boiling. So I turned off my car and I heard pressure being released. The water boiled for like 15 more seconds and stopped.

So my question is, what do you guys think is happening?? Why is the water/coolant so hot that it's boiling in my reservoir. I don't believe any of the main big hoses has holes in them which would cause my car to loose coolant. I'm pretty positive it's not my head gasket since it was changed about a year ago, or less. When I bought the car it had about 81k miles on it. I asked the man who sold it to me what he had done it it and told me the waterpump and timing belt were changed at about 65k. He gave me a receipt to go with it. Can it still be the waterpump?? Can the thermostat cause this??

Your help is appreciated. Thanks.