2000 hundyai elantra

its getting to hot try a tinfoil or something to keep it from getting so hot you need this Engine Control Unit

MOST TIME CHECK ENGINE LIGHT COMES ON WITH NO CODES,POSSIBLE CAUSE PCM GETTING POOR GROUND LOOSE GROUND OR CORRODED WIRES.

Hello Guest and thank you for asking your question, on Fixya.

Here is a simple process that will walk you through a few steps that will pinpoint the overheating problem on your 2000 Hyundai Elantra, without even using any tools. It has helped millions of people, and I am certain that it will help you, because I wrote it for people in your exact situation.
How to diagnose your overheating 2000 Hyundai Elantra

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Thanks for the vote, and good luck!

compression test, coil issue,

Did you scan for any trouble codes? Whenever the 'CHECK ENGINE' (Service Engine Soon) light comes on, the ECU (Engine Control Unit) sets a Diagnostic Trouble Code (DTC). These codes identify the particular engine management system which caused the light to come on. You'll need to use/find an OBDII (On-Board Diagnostic) Scanner to retrieve any code which have been stored in the ECU computer. Afterward, we might be able to help you DIAGNOSE the problem and perhaps fix the problem.

Whenever the 'CHECK ENGINE' (Service Engine Soon) light comes on, the ECU (Engine Control Unit) sets a Diagnostic Trouble Code (DTC). These codes identify the particular engine management system which caused the light to come on.
You'll need to use/find an OBDII (On-Board Diagnostic) Scanner to retrieve any code which have been stored in the ECU computer. Afterward, we might be able to help you DIAGNOSE the problem and perhaps eventually fix the problem.

Almost every car(including yours) has a flow through ventilation system which means even with the air turned off air will still come through the vents. Its hot because of outside temp and engine temp. 
Basically just push the recirculation button and it will stop.

If it has a 1.8l engine it should be 4.5 quarts.

The check engine light comes on because of an error detected by the car's computer. You need to have the specific error code read with a code reader/computer.

if it has a check engine light the simplest thing to do would probably go to auto zone or advance and ask them to do a code check,its free and will probably tell you the problem and take allot of the guess work out of it.