Fan problem

97 GLS Sedan manual tranny 165000 kms
I´ve had this car since 98, bought it with 25000 kms. I am very satisfied with the car, since it has been very reliable. I use it every day to go to the office, which is 45 kms from home. Nice mpg, never left me stranded.

Two days ago I was driving on the freeway and suddenly I checked the temperature indicator on the panel. It was almost reaching the white line that comes before the red section. If the letter C is 0% and the letter H is 100%, the needle was at 80%, when usually it is never higher than 50%.

I turned on the A/C to make sure the fan was on, and in ten seconds the needle was indicating normal temperature again.

When I got to the office I let the car cool down a bit. I opened the radiator cap and the coolant level was fine. So I decided to take the car to a Hyundai official service that´s close to the office.

We were able to reproduce the problem easily. All I had to do was to keep the engine idling and after a while the temperature would start going up. If I started the A/C the fan would turn on and temp was back to normal. We both concluded that there was some kind of electrical problem with the fan's circuit.

Since the mechanic was too busy that day he asked me to leave the car there and he would look at it the next morning. Unfortunately he was not able to reproduce the problem the following day. Everything was back to normal. He left the car idling for two hours connected to his computer and everything was perfect. The fan was turning on at 88ºC.

I brought the car home yesterday with the A/C off and the temperature was fine. The only difference between the two days is that the day the problem occurred the weather was hot and dry (30% humidity), and yesterday it was rainy and humid (90%).

Anybody have any ideas?

Mine had a problem where the temp would go hot, then back down to normal, but it turned out I had a leak in my radiator. You would know about that because the coolant level would go down. However, if there is a problem with your water pump or thermostat it could do the same thing. If it's a fan problem it could also do that.

There's also the possibility that your gauge is faulty, but probably not as likely.

My mechanic had problems reproducing my problem at first, but once they did it was fixed pretty quick. Good luck!

Another possibility is that the thermostat stuck partally closed. Just repalced one on grandson's 2001 Elantra as it tried to overheat and he turned the heater on full to keep temp down. New T-stat and all is well.

One more thought. I would guess (do not have wiring diagram handy) that there is one fan relay, and it works for both AC and overtemp. Having said that, there is a temperature sensor (probably on or near the thermostat) that controls the fan for over temperature and if it fails the fan will not come on as temperature rises. If I were a betting man I would first blame the thermostat.

After offering solutions, my grandson's 2001 elantra tried to overheat (he turned on heater and kept temperature below the RED level) and as he has an extended warranty he had it towed to a Hyundai dealer. Diagnosis a failed radiator so new one installed. Took car to work and it tried again to overheat (wouldn't dealer techs check out the system before releasing car). We changed out radiator hoses and thermostat and all was well for two days and this evening he went out to dinner (locally) and she tried to overheat again. I told him to turn on AC (to get fan working and see if temp came down). Tomorrow we will start her up and let her set and see if she tries to overheat at idle, also take her on road to see if she tries to overheat at speed (trouble shoot water pump). If she overheats at idle and fan does not come on, but does not overheat at idle with AC on (and fan on) I will assume fan relay is good and the collant temperature sensor is bad and therefore will not turn fan on. Any Hyundai techs out there, does this sound about right?

Bear, I gave up on this forum. There seems to be very little activity. I have moved over to hyundaiperformance.com and elantraxd.com.

Sounds like fan sensor to me. The fan is not coming on automatically that is why your car is overheating. The air conditioner forces the fan on and this is why it stays cooler when the air conditioner is turned on.

My 85 excel had this problem.

Thanks for the response, I replaced the thermostat and this stopped the overheating issue, but we still had a check engine light so I took her to Auto Zone and she coded a coolant temperature sensor, ordered that and will install this weekend.