I have a 2001 saturn sc2 and have had an on going issue for the past few years off and on. If I let my car idle for too long say at a drive through or stopped by a train, steam will start to rise from the passenger side of my hood and as soon as I kill the engine I can hear as see the entirety of the content of my coolant resevoir dumping onto the ground. Upon inspection the cap of the resevoir has blown off and the tank is empty. This has happened multiple times and I have replaces the thermostat temp sensor, and a couple of hoses which stopped the problem for about a year or so. Recently however my car has had a couple of instances where I will start the car and it sputters, almost dieing, and it idles rough, and now it is dumping all of my coolant again't and popping off the resevoir cap. Huge headache ! Anyou help would be very much appreciated!!

 

1) Is the aux cooling fan under the hood kicking on when the temp guage is reaching a bit below 3/4 -- or at all for that matter?

2)To test, with the hood up, turn on the AC (this test will only work with a functioning AC system). The fan should immediately kick in and stay running the entire time the AC is engaged.

If it does not, either the fan relay is defective (swap with the identical one next to it to test), the fan motor is dead (test via straight wire to battery), the fan motor circuit is open (wiring issue) or your ECTS (coolant temp sensor or its connector or the circuit wiring is defective

As a secondary test, with the AC off, remove the squeeze connector from the ECTS and check for corrosion. Remove any found, then put a paperclip across the connector terminals. This simulates a VERY HOT engine temperature reading and should immediately kick on the aux fan. If fan works, suspect ECTS.

3) If the ECTS was not sourced from GM, its resistance vs temp properties are who knows what and are likely indicating to the PCM the coolant is not warm enough to turn on the fan, so it doesn't and voila -- mega overheating. The rough running is a trademark of ECTS failure. When they fail, they almost always indicate to the PCM that the coolant is -40 deg -- ALL THE TIME. The air/fuel mix is super rich and stays that way, causing starting issues, driveability problems, and a host of other fun things like overheating.

4) Do NOT start throwing parts and $$ at it. Do the tests outlined above FIRST, then post the results here, and we will go from there. You will save $$

 

moved to S coupe section