Here's the situation. About 2 weeks ago, I noticed that my temperature almost hit redline when driving home.
Did the basics, new radiator cap, flushed coolant, new thermostat (185 lower temp one).

It doesn't overheat, but what I did notice.. when idling, then temperature will continue to rise.. when it hits about 210 or 220ish (just above half) the two radiator fans will turn on and cool the engine down to the quarter mark. They will then turn off and it will heat back up again and continually do this. Before it would stay around the quarter mark and not fluctuate.

Any ideas why this would happen?


some side notes... My air conditioner hasn't worked for a few months (probably needs recharging, as it's cool for a few mins, then goes warm) and my Cat Converter has the same temperature on the pipes going in as going out. I know there should be a 100 F difference, but there isn't and I don't know if this would affect the engine doing what it does... I also heard that if you start the car, turn on the MAX a/c to full, the fans should immediately kick on.. they do NOT do this, only when the engine temp goes high enough.


Thanks for your help

 

The temperature fluctuation is normal. While your car sits there, there is no airflow through the radiator. Therefore the coolant has no heat being removed. Fans kick on which creates airflow through the radiator, cooling off the coolant. While driving, yes it should stay at the quarter mark.As for the cat... the only thing the temperature of the exhaust would affect, is the efficiency and lifespan of the catalytic converter.As for the A/C, it sounds like it needs a recharge. Fans should kick on anytime the A/C clutch is engaged. I need to look at some prints before I could tell you what might be wrong there.

 

So what are the signs that the O2 sensors need to be replaced? I never knew they also heated the exhaust...

 

Yeah, I'm a retard. Here's what I found on another site:

"Since OBD-II vehicles may have multiple oxygen sensors located some distance from the engine exhaust ports, these sensors are generally heated to speed the warm-up time period. The HO2S incorporates an internal electric heating element to bring the O2 sensor up to operating temperature quickly (under 35 seconds). Internal heating elements usually operate continuously while the engine is running to maintain an operating temperature of approximately 1292 degrees Fahrenheit to 1472 degrees Fahrenheit. Heated O2 sensors operate at a more consistent temperature and allow greater flexibility of placement locations in the exhaust system."

The heater is used to makethe sensor more accurate.



Click to read more---> http://www.asashop.org/autoinc/dec2002/mech.htm