Wierd Cooling Problem

I have a 98 Cavalier 2.2L. Lately I've been having trouble with it reaching operating temp. I did the normal things; replaced thermostate, coolant temp sending unit, flushed cooling system. No dice. It would run on the highway below 150 degrees. I was starting to think that I was just getting bad thermostats, until I tried something one day.

On the highway it was doing it's normal thing. I stopped at a stop sign, and then just layed it to the floor. I got it up to 60 mph as fast as it would go, then I just kept it there. Then, all of a sudden, I saw the temp gauge rising. For a minute I thought I screwed something up, but then I saw that it went up to about 190 degrees...and it stayed there! I thought maybe there was something in the cooling system that finally let loose from me pounding on the car. It stayed like that for about 5 miles, then I noticed the gauge start to fall. It went back to running below 150 degrees. Now I'm running 60 mph, and I punched it, letting off at about 80 mph. Then I drop it back down to 60, and I noticed the gauge start coming up again. It leveled off at 190-195, and it did it again for another 5 miles. It would repeate this over and over.

It has 160,000 miles on it, and I'm wondering if the water pump is getting bad. I don't believe it's ever been changed. The coolant temp sensor isn't in the block or head, but it's in a tube that comes from the motor. My question is, is the water pump not circulating coolant like it should? I've heard of stories where either the water pump impeller started slipping on the shaft, and I've also heard of the impeller corroding away. Has anyone heard of this? I'm gonna go ahead and replace it, since they are cheap and it's easy to get to, but I'm just wondering if I should just park it until it gets done.

a faulty waterpump would cause it to overheat. due to a lack of flow in the system it wouldnt cause it to cool off. did you add straight new fluid or did you dilute it. if you run the coolant at full strenght depending on where you live and how far above sea level you are it could be "supercooling" meaning that its not getting hot enough to retain tempature. the thermostat was a good place to start, try to thin the coolant.

Anytime I've had to do anything with the cooling system (which has only been a couple times), I've used premixed antifreeze. This isn't only an occurance that happens in the winter, so I'm not thinking that it is cooling off too much. I did forget to mention that one time during the summer it seemed to get really hot. My wife came home complaining of a burnt smell, and I found out that the insulation under the hood got really damn hot and melted, and it melted only where it was close to the motor. I asked her where the temp gauge was reading, and she said it was between 1/4 and half way. According to the temp gauge, it shouldn't have been overheating, but there are signs that it got really darn hot under the hood.

That temp sensor isn't actually in the block, which is why I'm suspecting a circulation problem. Maybe it could be blocked there? I would guess that tube that runs in front of the motor where that sensor is is about 3/4 inch or even a bit bigger, so I wasn't thinking that it could have gotten plugged, especially when the antifreeze looked brand new even before I did any work to it.

Is there any other place I could put a temp gauge? I'm thinking about just getting a mechanical gauge and put it somewhere else on the motor to make sure my gauge in the car isn't messed up.

My 94 does the same thing.I have blamed the temp sensor but replacing that did not change a thing.I was thinking a thermostat that was getting a little jerky in its old age.Beyond that,I cannot imagine what it would be.I will need to hook up the OBD scanner while its being driven and see if the actual temp is fluctuating.

If your 94 uses only one sensor for the gauge and what the computer reads, it's going to give you the same result unless you have a faulty gauge. What I would like to do is hook up a mechanical temp gauge somewhere else and just see what that one reads in comparison to the original. If I put it somewhere in the block or head (if it has a spot), then I can see if it really doesn't get up to temp or if that hot coolant is just not getting to the original sensor. If I can't find a place to put that temp gauge, I'm just going to try put it in place of the original temp sensor. If that one reads about the same, then I know it's nothing to do with instrumentation.

I actually just looked at the car, and it is wet around the water pump, so, after I put a new one in, hopefully that cures everything. Gonna plan on doing it tomorrow. I'll let you know what happens.

Well, I put in my new water pump today, and it seemed to almost completely cure the problem. It takes a little while for it to come up to temp, which could probably be since it's winter, but once it got up to temp, driving down the highway seemed to be no problem as it stayed at 190. The old water pump didn't appear to have anything wrong with it. It had almost no play in the bearing. It appeared to possibly have been leaking, but I couldn't tell if it was that or something else that had leaked on it (I had changed the thermostat not too long ago, and might have gotten some coolant on it). The new one also had a cast iron impeller, instead of the thin metal one of the old one. Maybe that could have something to do with it? I'm at a loss on this one. I'm happy that it's almost fixed, but I'm just wondering why it was fixed since the water pump didn't look like it was the problem.

My '96 Cavalier has had a similar problem. I haven't bothered to fix mine because it isn't really a Problem so much as a nuisance. But, here's my theory. Our cars don't use normal antifreeze. Our cars take the orange anti-freeze instead of the green. If the two types are mixed they gell. Now, although it's supposed to take the orange stuff, my car and one other I know of had the green anti-freeze in them. Mine runs hot in the summer and cold in the winter. The car will run with either but is designed for the orange stuff. You should check and make sure it has the corect anti-freeze in it, it'll say on the overflow which kind it takes. Good luck, I can't figure out why my headlights won't stay on.

It was dexcool (orange stuff) to begin with, which is what it says it needs. After changing the thermostat, and then the water pump, I used the prestone that mixes with all makes all models. Before anything was done, the antifreeze was very much orange, so I'm pretty certain that the regular green stuff hasn't been added. But, just incase it has, maybe I should run some cleaner or flush through the system. I will be changing the radiator hoses (for my piece of mind considering the mileage), and the thermostat again because the problem seems to be slowly coming back. The first couple days it was fine, but now it's going back to the same problem.

I am wondering something about the flush that I should use. What kind can I use where I don't have to run straight water? I know a lot of them you need ot drain all the antifreeze out.

Straight water is what you're supposed to use to flush the coolant system. And, as far as I was able to tell, you have to disconnect at least the bottom hose to drain the radiator. The car should run with either anti-freeze in it, as long as the two types aren't mixed. A local auto parts store should have a kit for flushing the coolant system, they aren't too expensive.

It also occurs to me that cooling problems often have causes unrelated to the coolant system itself. Bad thermostat, or bad temp sending unit, excess carbon build up, fuel mix problems, the little electric fan on the radiator, anything that adds work to the engine will affect the temp. Could be a problem with the OBC. Could even be as simple as a bad fuse, a short in the wiring, or even a worn belt. That's why I say take it to a mechanic. I've spent years chasing down car problems using the hit and miss method. In the end, you usually won't solve the problem that way. My mustang is a great example. I spent almost a year trying to fix an electrical problem, the car wouldn't hold a charge. In the end, six hundred dollars later, I had to take it to a shop. There, I found out that the problem wasn't in the electrical system itself, it was the electrical load I was trying to make it push. For some reason it kept frying my alternator. 50 dollar repair job that I blew $650 trying to fix. My suggestion is to find an HONEST mechanic, and ask him to figure it out and report back to you before repairing anything. We aren't all Mr. Goodwrench, in fact most mechanics don't quite make that grade. But an honest mechanic won't do a job he isn't qualified to do, and can tell you who can. Further, as a newbie to car ownership, I can give you one good piece of advice, when you do find an honest mechanic, stick with him. It'll save you money and headaches later. Again, hard learned experience from years of beating my cars to death. My mustang had an overheating problem, truthfully it still does. So far I've replaced the radiator with a larger radiator made for a GT350, replaced the factory fan with a six blade, shortened the fan spacer to increase the amount of air being drawn through the radiator, I'm meticulous about the coolant mix I use, cut the lower air dam to increase upward airflow into the engine compartment, replaced the thermostat, temp sending unit, thermostat housing, heater core, and I've tuned it to run cooler. The only thing left for me to do to it is try to find a fan shroud that will fit my radiator/fan/spacer combo. If that doesn't work, the engine needs a thorough tune up and maybe a valve job. Look at what I've done to stop the car from overheating, all to no avail. Well, it does better, but it still dumps coolant if it's run hard at all. Hell, I even rebuilt the tranny and removed the grill work to increase air flow. I know it can be cost prohibitive to use a mechanic, I live in that economic class myself. But, I've found that in the long run, if you aren't a mechanic yourself, it's cheaper, faster and you get better after performance if a professional does the work. Again my mustang is the proof. We have a specialty shop locally that does nothing but Mustang. I never used them because I figured they'd be expensive. I was wrong, but I lost a few thousand dollars without actually getting anything really fixed bouncing from one shop to another looking for someone who would actually FIX the damn car. Eventually I had to try the specialty shop, they ended up being cheaper and much much faster, plus the work they've done has been done perfectly to factory specs.

What was the problem that your mustang actually had?

I don't completely disagree with what you are saying with the mechanic idea, but finding out what your problem is and how you went about fixing it at least taught you a few things. All mechanics go through the same stuff. I'm sure most mechanics have spent hours on some vehicle trying to figure out something that, if you knew what you were looking for, would take you 10 minutes to fix. Trial and error isn't all bad...you learn more from mistakes that you do doing everything right (maybe that's because people make more mistakes than anything).

a faulty waterpump would cause it to overheat. due to a lack of flow in the system it wouldnt cause it to cool off. did you add straight new fluid or did you dilute it. if you run the coolant at full strenght depending on where you live and how far above sea level you are it could be "supercooling" meaning that its not getting hot enough to retain tempature. the thermostat was a good place to start, try to thin the coolant.


i can under stand his problem i have a 98 with the same problem, i had waterpump changed and all the sensors and the thermostat and no beans i dont get it runs well below normal, i mean i dont have numbers just C,normal,and HOT and i run just a little over C not much though, i have a 50/50 mix of coolant and water and still no change but im used to it and it doesnt seem to hurt the car so until someone tells me that it is real bad for that im leavin it cause runnin cooler is better

Remember...cooler is better...up to a point. Cars are designed to run at a certain temperature to run efficiently. I'm not sure exactly what temp most are supposed to run at, and I know it's a little different depending on the motor and how it's put together, but a motor running at a little over 100 degrees is not good. Oil also has to be in a certain temperature range to efficiently work the way it's supposed to work. That's why it's always good to let a motor warm up some before you start driving it. Cars that are just started up and are running for less than 5 seconds before you start your normal driving tend to not last very long in comparison to vehicles that have a chance to warm up before you drive them. The components in the engine have certain clearances between each other. The clearances are different between a warm and a cold motor.

My point is that if a car is designed to have, say, a 195 thermostat (which is where it starts opening, not how hot the car is supposed to run), then it probably is supposed to run at around 200 or 205 degrees. If that same car is running at 100 degrees, there is something wrong. not only will you probably see less life out of the motor, but you will probably see a lot less gas mileage in a car with electronic fuel injection, since the computer still thinks it's warming up and feeds it more gas.