Is there a product my mom can buy which might plug the leak, even if it’s only a temporary fix?

My mom has a 1987 Ford Taurus, lately its been giving her a problem with overheating. The engine overheats until the heater in the car is turning on then it’ll draw off heat off the engine somewhat, but if it still stands at a light too long it’ll begin to run hot (or sit long anywhere for that matter.) Once we start riding, it’ll get cool again unless its 3/4th’s of the way up to the "H" then it’ll sort of cool off once riding, but it’ll go slowly… what is wrong with this car?

P.S. Sorry I’m having so much damn car troubles.

The car hasn’t run for 2 years now (not by our [my finace and I] choosing, my parents own it now and they don’t make good decisions). When we owned it in Flagstaff, AZ it would overheat whenever we went slower than 15 miles an hour or were stopped for an extended period of time. We would put coolant and water in the radiator and wait for it to cool. We had the thermostat changed, but the problem still occurred. We eventually determined that the fan was out, because we could drive long distances with no problem. We dealt for a while, and then gave it to my parents, in Phoenix. One day my mom was driving it and it overheated more often than usual. The last time it overheated, water came out the tail pipe. After that it never started again.

I will take it to a mechanic if it is plausible that the problem is fixable for less than the cost of the car. Any help or opinions please?

I have an 86 Oldsmobile in my yard that I want to work on. Problem is that it has a blown head gasket, no fan, rusted cylinder’s, and a busted window. My mom gave me her 1991 ford taurus, all it needs is a heater core and a new front suspension, other than that I got it running good. So should I still try and get the Oldsmobile running or stick with the taurus.

P.S. I am only 15 so I don’t have much money.