overheating problem

[papa karl]

Ok!! Got the thing running again with 135 PSI on #2 cylinder, but the rest were 150 (don't care now cuz it's COLD). Ran with water and without the thermostat for a day or so, but the temp sensor went out after a couple of hours (coolant ---F on the display), and MAF came up for a while. After clearing the codes, now I just got the temp sensor problem.

The car runs great now with a little heat, and no gurgling/bubbling/weird noises from the heater core, and first and foremost, no bubbles in the radiator tank.

So thanks for all the input!! Gotta go replace the chain tensioner, fix the temp sensor, fix the front left speaker, and look at the tire pressure thingie on one of the tires.

Thanks again

 

[YelloEye]

Temp sensor is probably just unplugged, though they do fail. Glad you got her running.

 

[papa karl]

Check this out guys!!!!

Changed the 'stat and temp sensor but still have the "--- F" reading. The ODB 11 reader shows ETC temp as 88 (when its 55 outside) when the car was cold. If I unplugged the sensor, the reader shows -40.

My volt meter shows 5V on the unplugged cable. Both sensors show about a 3K resistance in the cold, and goes to about 2.6K if I hold the sensor in my hand to give it some heat. I guess the resistance goes down when the engine is running.

I disconnected/reconnected the battery and VOILA!!, the computer now shows 88. Started the car, and noticed the radiator fan quit running, and the check engine light went out (after about an hour). OK!!, life is good!!, but not for long!!

Seems I have a loose wire, hopefully at the temp sensor connector. Some guy on another forum said the computer really doesn't like big changes in temp readings. I imagine the computer is reading, say 180, then quickly goes to -40 (open circuit) then goes back to 180. Well, the computer figures out this aint right, and shows --- until we reset the computer (or ???).

Hopefully this helps the bunches of people out there with this problem, apparently there are lots.

Does anyone know if the temp sensor connector comes apart?

Thanks

---------- Post added at 10:54 PM ---------- Previous post was at 09:14 PM ----------

I forgot to say in the last post that while measuring the 5 volts with the volt meter, I noticed the voltage was jumping around a bit, so there's something wrong with the connector, I hope.

Thanks

 

[YelloEye]

Dang, that's odd. Glad you got it fixed though.

 

[D.MORRIS]

so what is the normal temp for a 2007 cobalt to run? mine has been running about 240 and it blew two fuses for the ac unit. any body else experience this or no what may be wrong.

 

[YelloEye]

~210 the rad fans kick on, anything above 230 is worrisome.