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04 optima 4 cylinder automatic.
New Thermostat. New Radiator. New Sending Unit. Will sometimes drift into the red and then back down to normal. I put an analog gauge and saw that the real temp is sometimes rising to 200F. If I turn on the heater it will go back to normal area. Any ideas?
And now, update your profile, please, and then - if did not find explanation on the forum (try search other cars too - overheating is universal problem) - provide much more details.
Such as when does it happen? A/C is working? Is the system pressurized? and so on...
The car (temp gauge) seems to drift high when the AC is on and in idle - but it will also drift high (into and close to the red) going down the road. First we had the sending unit replaced - but it still happened. Then we put in a new thermostat - it still happened. Then we replaced the radiator. It still happened. Today I put in an after market sensor and gauge so that I can see how high it is really getting. It first settled in at 185F when the AC was on and in idle it drifted to 200F. (Is that an okay operational temp?). I turned on the heat and hot air comes out and the temp settled back to 185F. I replaced the original sending unit and now I can't get the problem to reoccur.
have you ever noticed that before?
Well, this temperature (185F is 85C) is normal, low normal operating temperature.
200F (93C) is not too high though. Water boils at 212F (100C), but coolant has higher boiling point (230F, 110C) in pressurized system.
So, it is not overheating yet. If you do not go over 95C, 203F, you should be fine.
You see, the thing is that in the front of coolant radiator is A/C radiator. If A/C radiator is hot then air cooling A/C radiator first will be already hot when reaches coolant radiator. This makes coolant hotter and forces fans to stay on.
Here is the trick. A/C has to be fully charged (not OVERCHARGED nor UNDERCHARGED) so that A/C radiator does not have to cool A/C fluid all the time.
Overheating will take place when A/C is not fully charged. A/C compressor will be constantly on or with very short breaks. A/C radiator will become hot, much hotter than it should be - and rest you know...
Have A/C checked by someone who is able to check BOTH - high and low pressure.
But as of now I would say it works fine.
BTW. My 2007 Rondo gets around 82-85 while driving, idle (on hot) may get to 93. When A/C is on while driving not less than 85, normally around 87, idle up to 95. And it is a new car (well, 1 year old). All temp in C.
Conclusion - It was the connector to the temperature sending unit. Bad connection was causing problems. Now that the connector is in another position no problems. I plan to get a connector from a salvage yard and solder in a new one.
need to pick my fellow Optima owner's brains a little more on this issue
I need help also...I also have a KIA, 2004 Optima 4 cyl AT (same as the poster of the original question of this thread), and I'm having very similar issues with my car overheating-however what's different with my car (that even after researching on this site I really haven't seen a thread which someone has had or addressed this scenario) is that it will NOT overheat if I turn/keep the AC ON, either while driving or at idle...specifically once the car is warmed up, on warmer days (70+ deg F) the temp gauge will rise from normal operating temps (the same as what's been previously mentioned in this thread) to pegging in the red (at least on the times that I let it or didn't catch it until then on accident), especially under idle...now if I turn on the AC while the car is overheating, the needle eventually stops rising and lowers back down to normal operating temps...car has 45,000 miles on it and is only driven (mostly city) up to 15 miles a day, and what I've tried so far to correct the issue is: radiator coolant flush and fill (and it's full), new coolant temp sensor, new thermostat, and new radiator cap...car has no leaks, hoses are in good shape (and do not collapse when engine is hot and running), and car runs smooth otherwise...also this whole time the CEL has never lit up...I'm not really sure that what was suggested previously above could apply torward my car also...otherwise could it also/either be a bad gauge, bad ground, bad water pump or something else I haven't thought of? Thanks in advance everyone
Do one test. Warm up the car, or after you drove back home, when car is still hot, turn off the A/C and observe (carefully) both temp gauge and listen to radiator fan.
Another thing you may do. In city driving let it ALMOST overheat and when it gets to this above normal point, drive it on HWY or at least for 3 minutes with speed no less than 40 MPH.
From this what you say I can conclude the radiator fan does not turn on when engine gets hot. BUT it will start working when A/C sends impulse that A/C radiator has to be cooled down.
So, I am not sure but maybe the relay is faulty (does it have separate relays? I doubt...)
I need to check, or you do that on the car, if radiator has a temperature sensor. Some cars (older ones) had sensor in radiator that activates the radiator fan. It could be faulty.
And one more thing. Does it overheat? You see above, the car actually did not overheat, but the gauge was misleading.
Wow thank's for the quick response and tips PLP...Yeah I was thinking that it also may be a possibility that it's actually not overheating but only acting like it is...unfortunatley I don't have the tools or knowledge to figure out how to figure out if the car is acutally running hot (without actually relying on the gauge itself)...in the meantime I'll try out your other suggestions and post what I find out...Thanks again
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04 Optima Overheating
Rondo PLP
Linear Mode
