Temperature gauge

I have a 93 Chevy Cavalier and the temp gauge usually stays at about the fisrt notch, but lately it has been going to the half way notch and it concerns me. today it almost went to the halfway notch and stayed there for about 10 minutes or so before it started to go down. I had a problem like this before. It would go to the halfway mark and then down to the first notch, back to halway and then down. It wasn’t too long after that my water pump failed and I replaced it. What is causing this. I was doing city driving today, mostly go a little ways, stop, wait, go, stop, wait. Could my thermostat be getting bad? And where is that thing? Do I have to rip half the engine apart to replace it? My water pump is about 2 years old now. My e-mail address is joemahma1234@yahoo.com

@Dogface it certainly sounds like it’s time for a thermostat. The thermostat’s job is to maintain proper operating temperature, once it’s reached. You’re also wasting fuel if the thermostat is faulty.

Look for this. The thermostat’s located underneath.


While you’re at it, replace the cap and do a complete drain and refill.

I use to have a 95 Cavalier. And when the temp gauge started acting wonky, it was a head gasket.


My Corolla does this, but it’s normal on the Corolla. Driving on the freeway at a constant speed the guage will register about 1/3 of the way up, but in stop and go city driving it will go up to 1/2 of the way. The reason is that the engine cooling isn’t as good in stop and go driving, as the airflow is reduced to the radiator. It would go more than 1/2 of the way up except that the radiator fan kicks on in stop and go driving. So cross your fingers, maybe nothing is wrong. Good idea to check that your radiator fan is working though.

Thank you. I don’t know how to check the radiator fan except open the hood. If it’s not running I guess maybe it’s not needed. I guess it is working because the temperature gauge does go down. You wouldn’t happen to know where the thermostat is would you?

First step.

Have you checked the coolant level?

@Dogface follow the upper radiator hose back to the engine. It should connect to the thermostat housing.

yes, I have checked the coolant level and it is right up to the top. The place that fixed my water pump did a good job, the coolant level has always been right up to the top and the coolant in the reservoir hardly ever needs adding to. I am wondering if it is time to change the coolant in the radiator. Is there a way to check to see if is doing it’s job right? It has been in there a long time.

thank for the tip on finding the thermostat by the way.

One more thing about the temp gauge. I had a Dodge Neon and the temp gauge would just immediately go to red line and then it would go back down. It would do this every once in a while. I changed the thermostat and it still did it, I changed the thermostat thinking maybe that one was defective and still had the problem. One night driving home the engine started to buck and make all kinds of horrible sounds. I was lucky to make it home. I found out later the head gasket was blown and that was why the temperature gauge was doing what it was doing.

When the head gasket fails, all sorts of things can go wrong. Oil can leak out, coolant can leak out, and extremely hot exhaust gas can be blasted directly into the coolant. Any or all of these events could make the coolant temp go up rapidly.

Yes, the way a mechanic would do a quick check on a radiator fan is to open the hood when the car is overheating. The fan should be spinning like a banshee. On my Corolla I don’t even need to pop the hood. I can hear a roaring-like sound when the radiator fan is on. But the car has to be idling for me to hear it. I usually can’t hear the radiator fan turn on if the car is being driven down the road at the time.

I don’t think it is the head gasket because right now anyway, the temp gauge has not gone over the halfway mark. One of the commenter’s said in stop and go driving, this is normal, I suspect that is the case with my Cavalier. Is my coolant still doing it’s job? Hmmm. there is a way to check that right. They have a gadget that can test that I believe.

Yes, there is a simple test for the coolant. The one I’m thinking of is only useful for indicating the freeze protection. It’s an little inexpensive device vaguely like a turkey baster to suck up some coolant and balls floating in the coolant indicate temperature.

The more important consideration is that the chemical aspect of coolant which inhibits rust, and probably some more esoteric chemistry factors, will wear out simply from age. Generally, that’s a few years, 3, 4, or a little more depending on the type of coolant used. The shop which did your water pump repair almost certainly refilled the system with fresh coolant just because you have to drain the coolant to replace the pump. It’s possible that they replaced the thermostat at the same time, hopefully you can find the paperwork and see if you were billed for the t-stat. Many people replace all the cooling system components, thermostat, hoses, radiator cap and maybe even water pump, when they change coolant. The idea is that these parts are relatively cheap and it’s better to avoid an overheat problem than to break down, and deal with the consequences.

So if it’s been just a year or so since you had the water pump replaced, your coolant is probably fine. If it’s 5 years, maybe it’s time to replace it. For many vehicles, the job is not technical, just sort of inconvenient, but not beyond the average do it yourselfer. Before you do, check your hoses and see if you want to swap the thermostat yourself. Find the t-stat housing just as db4690 described above.

On some vehicles, the electric fan comes on automatically when the a/c is turned on. Someone else here may know if that applies to your Cavalier.

PS: you might do the very simplest thing first, replace the radiator cap. It’s dirt cheap, non technical, no tools needed. Just be sure the engine is cold before you remove the cap. There’s a small chance the cap may affect the problem you are describing - probably not, but it’s the place to start unless you know yours is less than a couple years old.

I don’t think it is your thermostat although it could be. If it is, you might find it at the end of the lower radiator hose instead of the upper hose, that where most of them are now.

You can check you fans by turning on the AC. If you have two radiator fans, both should be running even if the engine is cool.

If the fans are working, then you might have a defective thermostatic switch, this is the switch that turns on one of the radiator fans when the engine reaches a preset temperature. Some times these switches are located in the bottom of the radiator, if so you will see a pair of wires going to the bottom of the radiator. More likely it is somewhere near the front of the head.

@Dogface your Cavalier uses the regular NON long life coolant.

I would change it every 3 years.