I have an 84 Monte SS with a 350 in it. It keeps overheating...I already replaced the thermostat. It was running fine until a couple days ago. The other day the radiator fluid overflowed out of the reservoir tank after i cut the car off. Any ideas how to fix this problem?

 

clogged radiator or pipes possibly

 

Sounds like the water pump to me. Do you have a temp guage?

 

Couple of thoughts....

Watch the radiator hoses and have some one start the car. I believe if either of them "suck in" for a moment, you havea clogged radiator (I had that on my 305 in my Camaro years ago).

But the fact you have coolant over flowing from the over flow bottle concerns me. In my experience, either that coolant was boiling over OR you hadtoo much pressure in the cooling system. I had a similiar situation with my '94 Grand Am (which I feel is vastly different then your Monte, but same concept may apply), my cooling system would have too much pressure and on that car the over flow bottle is part of the radiator (the radiator on that car does not havea cap, the overflow bottle holds the pressure). As a result of the over pressure, coolant would poor out of my cap after I drove about 20 miles to work. The problem was failed head gaskets (1 or 2 cylinders were forcing compression into the cooling system causing too much pressure).
Other signs of a bad head gasket would include large clouds of white smoke when you start the car (had that about a week before I got the answer to my Grand Am issue), oil appears milky from the coolant mixing with it.

 

I always had to "Burp" mine - as pockets of air got trapped. I had to pull cap-off several time before it reached operating temps. Wear gloves & eye protection ! Like Maniac said above -watch the radiator hoses - if they are old or weak - the will colapse...