ok, i flushed my radiator, added some radiator cleaner and water, let it run for 3 hours like it said i was supposed to do. afterwars i drove it for a little bit (maybe 20 mins) then i pulled it in the driveway and popped the hood and my overflow tank was literally BOILING over. my friend suggested we replace the thermostat, so we went and got a low temp (160 degree) thermostat and ran it agian. it seemed to be running fine. think that the thermostat was bad and i fixed it? or do u think its something deeper? thanx for all the help

 

So....you can idle in the driveway for 3 hours but you can't drive for 20 minutes?

 

More than likely, you fixed it by changing out the thermostat.

I've never tried it personally, but I hear you can take your (possibly bad) thermostat and toss it into a pot of boiling water. If it opens, it's working. If not, it's stuck (bad).

If it runs hot on you again after replacing the thermostat, the next thing to check is your hoses. If they are getting wore out, they'll collapse on you when it gets hot. If they've been there awhile, I'd suggest new hoses.

After flushing the radiator, changing the thermostat and hoses and it's still running hot, then I'd say either the radiator is so stopped up that flushing wasn't enough to unstop it, or you got a bad water pump.

 

I'm with Nick on this. It simply does not make sense that you can idle the car in the driveway for 3 hours without it heating up, then can only run it for 20 minutes at highway speeds before it heats up.