cavalier 98 overheat, fan bypass and alternator burnout

ID Status Date Year Make Model Transmission Type A/C Controls Public/Private
#16705 Closed 1998 chevy cavalier public

i am have a 1998 chevy cavalier auto trans. 2.2
I have been battling the last 2 years with the temp issues that it has. When i bought it, it kept overheating, so i noticed that the fan wont turn on unless the engine temp reaches 107 C around 224f, which defies any order of physics, so according to several months of research, this car is suppose to run above boiling water temperature, but to reduce this, chevy says the users are supposed to put ONLY ac delco antifreeze or coolant with a 50/50 mixture, which i have done with no positive results. After that it was deciced to connect a temp switch controled relay on/off system bypassing the car´s wiring, but, it keeps burning the alternator components, specially the voltage regulator, which is also defying because the system works well with the ac turned on, 24/7 and the fan is turning like crazy and the temperaure actually decreases to half of normal operating tempeature. Other guys have just decided to keep the fan on with a bypass permanently, which is actually worse.

i have no coolant loss, so no head gasket issues, the fan turns 100 when it is activated, the water pump is new, the coolant reseorvoir is fine, new, cap, everything related to the cooling system is fine,, i use synth oil, 15/40, one thing though, the cluster temp gauge works fine,, the temp gauge does show the actuall temp, but the bypass swithed relay system turns on at 95c, which is the default for that generic bypass gauge, while the cluster reads below 85c, i had to change the original ac delco sensor because the connector was brittle and broke, so i used a replacement made in brazil, that actually works fine, point is the pcm reads the tempa accurately but it is still above any law of physics, and i actually tryed 3 different brands because i did not know that the car was supposed to run above a 100 dgree mark, so..

how to overcome the alternator burnout because of the external fan system, it seems to cause to much of a amp load at fan start up, can i use a condenser connected in parallel to minimize the stress during fan start, ? It is obviuos that the pcm uses some sort of controlled start when the ac is turned on cause , the car wont stall or cause an amp shortage when the system is normal, that means , the alternator is working fine and no short circuits in the system, and no wierd fan bypass. which means the fan motor is receiving a lower amp rating from factory, than the maximum that it can actually use. meaning if the original wiring will provide only 1 amp to the fan motor via the pcm control, the fan motor rating is actually higher, up to 2 amps or more.( i guess around 5 amps). SO when the bypass is on, tha fan is turning with maximum watt output , and that “relay on contact” at max watt damages the OEM 105amp alternator,,
To me, buying an aftermarket 200 or 300amp is impossible and useless, first it is wildly expensive, over 300bucks, and the catch is that ALL alternators at idle dont deliver 200amps, that only happens above 2000rpms, so no alternator will widthstand a power surge of that kind at idle.. over time it will burn too, more sooner than later. The car was simply not designed to carry high output electrical parts. i mean they barely put one damn fan for cooling and AC,really!
is there any workaround this problem to try before i put this dog to sleep? i need my car, but it seems chevy engineers really missed several spots here, the other stupid solution is just to ride with the ac on ,, 24/7, and not to talk about fuel economy.
i now that there are places that tune the pcm so it will start at least 95c with the original sensor (203f) but it seems over the top to do this, to open a 25 year old pcm and modify it,? no sir.

i wonder how these cars have actually survived the 10 year engineered programmed death, and how they actually worked when they were brand new.

or am i doing something really stupid.. i mean im just human.

does someone have any wild idea as to how to control this..?


I want you to know that I have tried to reply several times but every time I write something and read it back to myself it sounds condescending.

From my perspective as a well seasoned mechanic, your Cavalier has some very simple problems and unfortunately you are overcomplicating them.

My advise would be to either invest some money and time into properly educating yourself or turning it over to a local qualified shop/mechanic.

my advise to you would be not to be on this web site if people like me are not gonna get any help.. its barely ignorant to asume that the car is not sitting in a car shop right now,, you see most mechanics really dont care about the problem they are facing, specially if the car is old and has electrial problems, and to land in a web site and get a shallow answer like this one is the kind of feedback that we get from most mechanics , and gets car owners into problems so we end up with a lemon car, thanks for the heads up, (and yes i made some mistakes about the fan amps its normally around 20 to 30) i am not a mechanic but i do hold a college degree and do not assume im a child,,either),, it doesnt take to much to understand basic electrical and thermodinamic principals to know that some cars are sh,, built, and assuming that engineers get it right all the time ,would mean that cars would last forever, most cars are designed in lobbys not in machine shops, they are budgeted to conform the least expensive materials and systems, but thanks for the heads up.. i suppose ill have to get back to solving this car problems on my own,, since most mechanics just dont give a damn because its not a tesla. You can google it in wikipedia,, cavaliers were shit built,, but i didnt know that until i got it. maybe ill just buy a myself an ford gt and problem solved… if you can figure out why a car is designed to open a fan after a 100 degrees, then you can be condescending. (please dont tell youserlf that the engine block alloys are suppose to be overheated always), right now i am being condescending.


Well, it would be kind of hard for me to not be on this site since it belongs to me.

It would be irrelevant if it were in a shop or not as you are the one asking for help and not a shop.

As for assuming that mechanics or myself do not care, I spent between 5 and 10 hours reading and re reading your questions and providing accurate feedback on another Q&A session you had with me about 7 to 8 months ago. I never asked for anything in return except for accurate replies to my questions about your car. Very few were given. If your were to go back and revisit that discussion you might see what I mean.

A little information before I go. Your engine and most modern engines are designed to operate at about 195F. This is due to Federal CAFE Standards and not because the engineers or manufacturers want your car to fail.

Your engine can operate well between 195F and up to 240F. When it goes up higher, there is a concern and going above 250F to 260F is not desirable. Above 240F is generally when the gauge needle moves into the red or hot zone or the coolant temperature light comes on.

Your coolant fan system is designed to turn on at 223F according to GM service information. There are several reasons for this. The first is the aforementioned CAFE Standard, that the vehicle manufactures have to comply with.  Second is that it would be a waste of energy to turn it on earlier. A lot of electricity, horsepower and therefore gasoline is consumed when that fan comes on. Once the car is back moving over about 45mph the engine will cool back down on it’s own without the help of the fan. In most cases the engine will not come close to hitting 223F while moving less than 45mph. Even at a full stop with an outside temperature above 90F it takes several minutes to reach that temperature in a properly functioning vehicle.

So, you are driving your vehicle and it is at 195F as you come to a stop. You sit at the stoplight for 1 to 2 minutes and the temperature creeps up to 218F before the light turns green. You take off again and in just a minute or two the engine temperature is back  down to 195F and no excess energy was expelled to do it.

Now, the engineers realize that you may be stuck in traffic and not moving for 10 to 30 minutes. Even longer possibly. The fan comes on at 223F and within a few minutes it cycles off because the engine temperature drops below about 200F. This cycling repeats itself until the vehicle is moving again. A turn on temperature of 223F gives the cooling fan plenty of cushion to keep the temperature under control and from hitting that dreaded 250F to 260F range. Waiting until the temperature got to 240F+ would limit the systems ability to keep the coolant from boiling out.

Now, this is where our discussions get interesting and why I hesitated to reply at all. Several months ago and in your very first entry on this discussion you mentioned in a round about way that the temperature is reasonably accurate. You also mentioned that the factory system turns the fan on at around 224F and that your “bypass” turns it on between 185F and 195F ( I did the conversions). Then you state that either once the vehicle is driven for a while or the fan is forced on with the a/c, the gauge reading will drop to about half of normal. That would put the engine temperature down below 100Fand not likely an accurate reading. Most gauges don’t read well in the low range.  So let’s assume for the sake of argument that it really only drops down to around 140F. As mentioned 7 to 8  months ago in my replies to you and right now. That is a classic sign of a missing or stuck open thermostat.  If the thermostat is installed and working properly the temperature gauge will never drop below about 180F to 185F unless the ambient temperature drops below 30F. In extreme cold it could go down to about 160F.

One other tidbit. If the thermostat is missing or stuck open the coolant can flow so quickly through the radiator it cannot cool down properly and the engine can run hot as a result . Not so much in older vehicles (pre 1970s) but absolutely in 1980 to present. The newer, the more susceptible they are which is one of the reasons the code P0128 exists.

I have to assume you must already know this though with your college degree and more than basic understanding of electrical and thermodynamic principles. Sorry, but I just had to put the condescending dig in.

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