coolant and temp problems.

Ive got a little problem so heres the info. When I bought my 94 c1500 (5.7L) It needed a new radiator. Before this was done though, I replaced the thermostat to see if that would help. This was three years ago. No problems untill now. My temp gauge rises sharpley to the red at random times even when the engine is not under strain (up hills). Also When I stop the coolant seems to be boiling back up into the resivoir. I can also smell it and it is very potent. I think there is even little puddles left behind. I have been putting a lot of water in it to keep the level up. Any Ideas?

If the thermostat was a cheap one it could be going bad already, take it out and suspend it in a pot of water with a thermometer and place on the stove, when the water temp reaches appropriate temerature, remove thermostat and see if it is open or not. another suggestion, drain the radiator into an open topped container by taking the lower rad hose off and observe the fluid and look into the radiator from the cap, if you see alot of corrosion, then you need a new radiator, you could have chunks being clogged at your thermostat. If thats the case remove the thermostat, put it back together and flush the hell out of your your cooling system, then do all neccesary repairs.

with your radiator a little low you can remove the cap while the engine is running and check out the flow. You should see the coolant moving pretty good in there.