this may be a goofy question BUT do you mean flushed the radiator not the heater core. Heater core is on the firewall.
Check the hoses going into the heater core to be sure they are both hot after the car has reached running temp. This will let you know if you have a blocked heater core not radiator.
Check voltage circuits. The ten amp fuses are for low beam. Turn on the headlamps, lo beam setting, use a test lite to check voltage on those two fuses. If no voltage may be problem with dimmer switch?
Repair the passenger door such that the warning light goes out. Either adjust the switch outward or adjust the door latch inward. If you cannot get the light go o out that way, you can disable the switch by disconnecting tbe cable, taping the connector, and tucking the wire back into tbe body.
When it won't start testing the electrical systems is the proper way to find a fix . Using a DVOM - digital volt ohm meter and power flow diagrams . Using voltage drop testing ! How to voltage drop test starter motor circuit How to test starter engine doesn crank GM 3800 engine Electric Testing Techniques You Need to Know
Do you know what a wiring diagram is ? Free wiring diagrams here http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model an engine size . Click on engine under system then under subsystem click on starting .Then click on the search button , then on the blue link . This is a wiring diagram of the starter electrical circuit. Do you know what ignition switch is ? the electrical part. , how about the starter relay , transmission range sensor ! There is one thing you can try , move gear selector to neutral an see if it starts then . If that does nothing ,check for B+ voltage going at the starter relay . Jumping pins 30 & 87 at the relay socket , where the relay plugs into . will cause the starter to engage an spin the engine . If you look on the bottom of the relay you will see four sets of numbers 30 & 87 - 30 should have B+ voltage , 87 goes to the S terminal on the starter solenoid . An 85 & 86 are the control side .86 at the relay socket comes from ignition switch through the trans range sensor to the starter relay coil ( electro magnet ) . Watch these videos too . VEHICLE RELAYS Testing from the relay base
whichever pulley it is sliding off of is not straight. check the alignment of ALL the pulleys and make sure there is no play in them. They should all be solid with no wobble. My guess would be a bearing is bad allowing play in the pulley which lets the belt "walk" to the edge.
Where is the knocking coming from?
If it is from the engine or motor, it should be a connecting rod or a main bearing failure.
To tell, get under the car with the motor running, and listen to the bottom of the engine pan.
If this is the problem, it ( the motor) should fail completely within a few miles or minutes, requiring a complete engine overhaul.