The car is injected and I changed spark plugs about a year ago but I already had the overheating before that. Likewise, the injectors were cleaned when the sparkplugs were changed. Did an exhaust gas test a couple of months ago and everything seemed to be OK. The radiator was fixed and unclogged a couple of months ago as well.
This is what happens. the car is small engined (1.1L) so you have to force it a bit, particularly when going uphill. About a month ago I was traveling on an uphill road (somewhat steep) with a full passenger load. When I was doing between 65-75 kmph in third gird with high revs and full throttle nothing happened. But as soon as I drove into traffic and had to slow down to 45-50Kmph (second gear, full throttle and high revs again) the overheating light would come on within a couple of minutes. This happened about 3 times during the 1 hour uphill drive. The first time I pulled over and turned off the car. I heard the cooling fan at full speed and it stayed that way for about 5 minutes or so before shutting down or going into low speed. However, the second time it happened I pulled over, turned off the car but as soon as I turned it off I noticed that there was no noise coming from the fan (BTW, my car is one of those in which the fan works independently of the ignition switch). As soon as I got down I heard it starting. That was certainly not normal as the car was supposed to be overheating. The last time it overheated I could hear the fan (or so I reckoned) but it stayed on for quite a while. As a matter of fact, I could touch the radiator, feel that it was cool (cooler than under normal operation) but the fan was still going at full speed.
So my conclusion was: the fan switch is damaged. Instead of going into second speed as it should it's shutting down completely. This made sense as I had no overheating problems when I was doing relatively high speeds, and therefore had more air flow to the radiator than when I was doing slower speeds with the same load. But we ran several tests on the switch with my mechanic and it seemed to be working fine. Which brings me to possible cause #2.
Some months back (before replacing the battery) I had a number of electrical problems. The main problem was that I couldn't turn on the car when "medium/high power" electrical devices (lights and cooling fan in particular) were on. I would turn the key and nothing would happen. The car wouldn't even try to start (as it usually does with a dying battery). I couldn't even hear the starter motor doing anything. Replaced the battery (as the old one was over 5 years old anyway) and the problem apparently stopped. I could turn on the car even if the lights were on just as it should. However, during one of these overheating stops I tried to turn on the car while the fan was running at full speed and I got the problem again. I had to remove the cover from the stereo, turn off the lights and even remove my foot from the brake pedal to avoid turning on the brake lights in order to get it started (as the fan was still going at full speed).
So possible cause #2 could be that there's some kind of electrical problem. Namely, when there is already some kind of load on the electrical system (car running, lights on, etc), a high load condition (fan at full speed or starting the car) cannot be met so, for example, the car won't start or the fan won't go into full speed. Only removing the initial load (turning off the lights, the car, the stereo) would allow for this "high load" demand to be met.
But the strangest thing is that this overheating only happens when I'm on uphill roads at relatively low speeds. It NEVER happens with urban traffic. No matter how hot the day is or how bad the traffic jam is. It is only under constant high load conditions that this happens.
What could it be? I'm really frustrated.
BTW, the cooling fan only has 2 speeds. The highest, which is the one I mentioned, is never used under normal urban traffic. With regular use it just uses the lowest.
BTW, sorry for the long post but I wanted to describe the problem as accurately as possible. Any advise would be greatly appreciated
