98 Saturn SL overheating

Change the thermostat for the heating problems. As for the hard to start when hot, check your air filter. Change your fuel filter and check the fuel pressure. Check your engine ground connection. Check the connections in your ignition system. Change your idle control sensor. Could be any one or combination of the above.

I know this is late....but in order to help others...
Most likely problem is the coolant temp sensor.
Easy fix too.
This sends info to the PCM to control many systems.
I had this happen 2x with our Saturns, and both times it was immediately fixed.
Problem could be the sensor itself or a corroded cap that attaches to its end.

Hope this helps someone.

Dean.

I know this is an old post but for the benifit of others looking things up I post an additional note.

If you have been overheating it can be because of 1 of 4 things
Low coolant
Blockage either solid or air pocket
Stuck thermostat
Failed pump either belt slippage loose or failed barring or impeller damage

Rough or hard start especially when hot may be due to a failed temp sensor located on the upper driver side of engine. The computer thinks it cold and dumps too much fule in the system and floods it. Runs rough and smokes a bit. The excess fule can wash the oils from cylinder walls causing premature wear .This is the 2 wire sensor that you can get from most auto parts stores for 6 to 10 dollars and is easy to change out.

Temp sensor just below thermo housing. I have seen this prob before.