[hunterprice22]

I have a 2001 Chevrolet Cavalier. When I'm driving the temp gauge goes all the way to hot. Mostly when I have my heat on and going uphill. Nothing happens to it. No smoke and the car doesn't act up. I recently bought the car and I've talked to the previous owner about it. They said it did the same thing to them. They got it checked and there was nothing wrong with the car? So I'm wondering whether this could be something major or the gauge is just messed up or something.

[odinn7]

It could be a thermostat. It could be the fans not coming on, It could be low on coolant, It could be a head gasket. It could be a bad waterpump.

What it probably is NOT is "nothing wrong" as the previous owner told you. This is most likely the reason that they sold the car.

You first need to check the coolant level and see if it's full then go from there.

[hunterprice22]

Okay thank you! Im leaning toward the engine coolant because I tried to get the cap off and it broke so I've went and bought a new one so I'm going to try to see if that's the problem. Everyone I have asked said it was most likely the thermostat. Thank you so much!

[odinn7]

If it is low on coolant then there is a leak somewhere and you will need to find that. Coolant is basically a closed system and is only low when there is a problem.

Anyway, check the level first and then come back and let us know.

[Mcsap9213]

Typically turning the heat on will lower it a little bit. Does the temp go down at all say when going down a long hill or when the outside temps are cool ?

[odinn7]

Turning the heat on only masks whatever issue is already there, it does not solve the problem. If the gauge is pegging in hot, there is something wrong and if it's not a head or head gasket yet, it will be if it isn't taken care of.

[TxGreaseMonkey]

Keep in mind that it can only take overheating an aluminum head engine once to warp the head, damage the valves, and blow the head gasket. Repairs can easily exceed $3,000. It's important to solve the problem, before driving the car anymore.

[odinn7]

Keep in mind that it can only take overheating an aluminum head engine once to warp the head, damage the valves, and blow the head gasket. Repairs can easily exceed $3,000. It's important to solve the problem, before driving the car anymore.

Great point. Sometimes in my effort to answer a question, I overlook the obvious and most important piece of advice. I know not to drive the car but I forget that others may not realize this as well.

Thanks for bringing that up.

[hunterprice22]

It will go back down at random times but I have to have my heat off to return to normal temperature.

[hunterprice22]

Also, the previous owner drove this car for many, many years with this problem too. Still not too sure what it could be but the car runs perfectly fine.

[TxGreaseMonkey]

It's a pretty strange situation, in that the engine's temperature should drop when the heater is on--it acts like another radiator to remove heat.

The solution may be that the temperature sending unit is bad. They have a thermistor inside that may be failing. It's easy and inexpensive to replace.

[hunterprice22]

It's a pretty strange situation, in that the engine's temperature should drop when the heater is on--it acts like another radiator to remove heat.

it is really strange. That's why in the first place I just thought my gauge was messed up and flipping out. Because it honestly makes no sense.

[TxGreaseMonkey]

First, I would remove and clean the connector going to the temperature sending unit. Second, it would spray the connector with WD-40 and reconnect it. Third, I would replace the temperature sending unit, if the problem persists.

[TxGreaseMonkey]

Temperature Gauge Problems

Background:

A temperature gauge is basically a voltage meter, controlled by the Engine Coolant Temperature (ECT) Gauge Sending Unit. The ECT Gauge Sending Unit contains a thermistor (temperature sensitive resistor), which regulates the amount of voltage to the temperature gauge. Since resistance decreases with increasing temperature, it is a negative temperature coefficient (NTC) thermistor. It will vary between zero volts (Cold) and 12 volts (Hot), depending upon the temperature of the engine. For identification purposes, the ECT Gauge Sending Unit has a one-wire connector going to it, while the ECT Sensor, which goes to the ECM, has a two-wire connector.

Troubleshooting:

1. Check all under dash and under hood fuses with a test light or multi-meter:

2. Remove the ECT Gauge Sending Unit connector, clean terminal and connector with abrasive cloth, and turn the ignition switch to ON. The temperature gauge should bottom at Cold (0 volts). Next, ground the wire from the sending unit--the needle should go all the way to Hot (12 volts). If it does, the fuse, wiring, and temperature gauge are fine. You will likely, then, need to replace the ECT Gauge Sending Unit. If it doesn't, then you have a fuse, wiring, or temperature gauge problem. Indications that the ECT Gauge Sending Unit may be failing are a fluctuating temperature gauge needle (thermistor breaking down) or a needle that barely moves.

3. An alternative, and possibly safer, way to test the ECT Gauge Sending Unit is to disconnect the electrical connector and attach an ohmmeter between the sending unit terminal and engine ground. When cold, resistance should be around 275 ohms. As the engine warms up, sending unit resistance should drop; at full operating temperature, it should read 18 to 20 ohms.

[Mcsap9213]

Using the heat was a test , not a solution :)

[odinn7]

Using the heat was a test , not a solution :)

Ok, gotcha. Now I understand.