Ok so my 1990 jeep cherokee 4x4 I6 is over heating i drive like 10 miles and it gets to the red so what do i do the heater doesn't work so i know the heater core is bad. then the second fan that is supposed to turn on when i stop driving does not turn on at all and also when i turn the car on the temperature goes all the way past red for a second and then drops all the way does that mean that the thermostat is bad even though the guy i bought it from just got i new one? please help i have to go to work tomorrow and i cant drive it

 

is it blowing water or steam out of your coolant resevor? other thing it could be is that you have a air pocket in your motor. its comin in these jeeps.

 

Sounds like something wrong with the fan. My cousins was doing this and he had a bad thermostat AND fan. He bought his, a 94 I think, used and didnt know much about it. Guy said it had a new thermo but still overheated. So, he changed it out and it helped a little, but his fan was burned out and he had to put a new one it. Other than that, 245K on it for $400 bucks and hardly any rust except a little surface stuff, not a bad deal. Id start smallest, cheapest, easiest first and go from there.

 

T-stat is just 1 of the 5 major cooling system components:

Radiator
Water Pump
Fan Clutch
T-stat
Coolant

How old is the rest of the cooling system?