Engine Overheating

Issue:

Overheating. I have had this problem for around 2.5 years. I'm not sure what could have caused the problem - one day while driving, I just noticed that the temp gauge was approaching the red. My driving habits hadn't changed (average around 5k/year mixed city and freeway driving), nor had anything (i.E. Damage, collisions, etc.) Happened to the car.

The car tends to overheat after about 15 minutes of city driving, but has overheated on the freeway, as well (this occurs less frequently, however, because the constant air flow when traveling seems to keep the engine cooler). When the car overheats, the cooling fans will not turn on. To cool the car down when it overheats, I will turn the heater on high. Upon doing this, the temperature gauge will drop fairly quickly; however, I must then keep the heater on to prevent the car from overheating any further.

When the car overheats (while the car is parked with the engine running), the temperature gauge will rise about 8/10 of the way up, then the fan(s?) Will kick on. The temp gauge will then fall to about the midway point. The fans will then shut off, and the temp will rise again. This cycle lasts around 3-5 minutes and will repeat itself for however long the car is running.


Repairs:

I have taken my car to several mechanics, yet NONE has been able to diagnose or reproduce the problem. Every time the car is in the shop, the fans will turn on properly. The last mechanic I took my car to even drove the car around town a few times, but never witnessed the car overheat until I drove the car directly to the shop myself after it had already overheated.

The first set of repairs I had done to address this issue were: coolant/radiator flush, new thermostat, new timing belt, new waterpump, new alt. Drive belt, new p.S. Drive belt, and new a.C. Drive belt. Also, the mechanic inspected to make sure that there were no blockages in the hoses. I’m not sure if each of these was done to address the issue, specifically, or if they were done simply as some sort of maintenance. Either way, these repairs did not solve the problem. My car would still overheat.

The second set of repairs was done 9 months later. This time I had the coolant fan switch replaced. This seemed to fix the problem. My car didn’t overheat for nearly a year. Well, a few weeks ago, it began overheating again, and so I took it to a different mechanic.

The third, and most recent, set of repairs involved replacing the entire fan motor unit, the fan switch, and the thermostat (again). These mechanics said that although they weren’t sure what the problem was or how to reproduce it, the repairs they made should fix the problem. They didn’t. The car overheated on the way back.


Other Notes:

The coolant level has always remained stable throughout this ordeal.

The radiator has never appeared to malfunction (after speaking with the mechanics about overheating, some suggested feeling if the radiator had any cold spots between the fins. Mine did not. Nor has any mechanic felt that this problem lay with my radiator or engine. Granted, they had no idea what the problem was, I just felt that I should point this out, for what it’s worth).

The oil has always remained the same color (the color of oil – not milky or grimy); however, after the car overheats, the oil level tends to drop slightly. The car is not leaking oil, however – or at least that I can tell. There have been no oil stains, residue, or drops underneath my car noticed by me or any of the mechanics I have used.

The car can produce a smell when overheating. Usually it smells sort of metallic. The mechanics I’ve used said this smell was boiling coolant.

After taking the car home from the mechanic, it overheated again. I pulled over to look at the engine. I noticed neither fan was on. I turned the heater on, then both fans switched on. I turned the heater off, then both fans switched off. I turned the air conditioner on, then the driver’s-side fan switched on. I turned the air conditioner off, then the driver’s side fan switched off. The same happened when I turned the fan on and off (the coolest setting without using the air conditioner). I then turned the heater back on, but this time only the driver’s side fan would turn on. I’m not sure if this is what happens each time my car overheats, but I did notice it today and have noticed that my fans weren’t on upon prior occurrences of engine overheating. Engine overheating