Steps for replacing the heater core in a 1997 pontiac sunfire

check for the connections on the ignition switch
if it starts then when you let the key go it stops ,that indicates that the run circuit of the ignition is not complete

Replace the bad thermostat you bought.

hello! I had the same problem with my 2000 Pontiac Sunfire... there might be one of these 2 problems with it.... maybe the Heater Core is jammed and the coolant dosen't flow thru the engine to cool it off, or the water pump is defective.... does the heating works or not? if yes, the water pump is defect, if not, the heater core is jammed, try a ''radiator hose cleaner'' (sold in Napa's or Carquest..) it will act as a kind of ''decloaker''.. if works, good! 15$ solution... if not, replace Heater Core... ~150$

You need to replace the thermostat. This is what regulates the engine temperture. It should be around 180 to 200.

First of all, make sure the heater core isn't air locked. With the engine running, and your heat temperature on high, loosen one end of the heater hose and see if you can get the air out of it.

there is a steel pipe that runs across the motor there, they are prone to corroding and leaking, you might get away with cutting it and bridging with a piece of hose but the best bet is to replace it. We have been lucky a couple of times and found a car in the wreckers that had newish ones fitted.

either the heater core has sprung a leak, or the hose and its discharge is shooting inside the passenger compartment.my bet is on the heater core.you can by-pass the heater core.
remove both hose's that go to heater core and connect hoses with a piece of tubing, or make a loop with on hose to connect both water outlets .

1. drain cooling system
2. disconnect heater hoses from engine side of firewall from the heater core,
3. remove nessicary dash panels and covers to access heater box.
4. unbolr heater core and remove.
5. reverse to install.
6. fill cooling system, making sure to purge the air from the cooling system.
7. YOUR DONE

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/sean_54c3a3dc48a7773c

This is a fairly easy fix. Disconnect the heater hoses under the hood. Go to passenger side under the dash remove the lower panel from the dash to access the heater box. Unplug any and all connections on the lower half of the heater box and remove the lower half of the box should be about six screws you should see the heater core and the evaporator core. Heater core skinnier of the two should have one or two straps holding it in remove the straps and remove the core and replace.

there are 2 hoses that enter the firewall connect them together and your problem is solved just no heat for you. otherwise spend 8-10 hours ripping out the dash and spend 40 bucks on a new heater core. then 8-10 to put it back together again.