Q: My car overheated this morning, completely drained the coolant and replaced but still fluctuating to half and below half

asked by on January 08, 2017

My car overheated this morning, we let it cool completely and drained the coolant and replaced it with coolant and some Lucas super coolant but the temperature is still fluctuating to half and below half when we drive. Since we changed it, it has not overheated but I don't understand why it's fluctuating. Could it be a faulty thermostat?

My car has 162468 miles.
My car has an automatic transmission.

If the fluctuations in temperature are relatively rapid, that is not typical of a failing thermostat. It’s possible there is a temperature sensor fault, wiring issue or gauge problem that makes it appear as if the engine temperature is fluctuating but in fact it isn’t. Having said that, if the thermostat is original, and you’ve had cooling system "issues", it’s definitely wise to replace the thermostat as part of the diagnostic. The key thing of note is thermostats do not last forever and, indeed, when water pumps are changed out, unless the thermostat happens to be new, it should be changed as well. Fluctuating temperatures, or overheating, can be caused by a loose water pump drive belt, a defective water pump, and trapped air in the system so you want to be sure all air is purged. Finally, if the electric cooling fans are working erratically or there are problems with engine tuning and engine management systems, that can cause temperature fluctuations. I think your best bet, because you started off with overheating and are indicating that the cooling system is still not operating stably, is to request an overheating diagnostic. The responding certified mechanic will consider all the possibilities, including temperature sensor and gauge malfunctions, and the mechanic will also advise you as to the wisdom of changing out the thermostat.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

How do I adjust the temperature?

The temperature is adjusted with the Temperature Control knob. Rotate this knob clockwise to increase the temperature, or counterclockwise to decrease the temperature.

Turn signal and hazard lights are not working. 2000 Chevrolet Prizm

Hi there if the fuse for the turn signals and hazard warning lights is good, the flasher unit - same integrated unit services both functions - is likely bad, and should be replaced. I would recommend a turn signal/hazard warning...

Locate master reset button on top of motor

Hello. The only sort of reset switch equipped on a Ford Expedition would be the fuel pump inertia switch. The purpose of this switch is to cut off power to the fuel pump if the computer detects a harsh impact,...

Related articles

A Buyer’s Guide to the 2012 Chevrolet Tahoe Hybrid
Chevrolet Chevrolet has always had a good name when it comes to the vehicles they make, and that is doubly true for their SUVs. The 2012 Chevrolet Tahoe Hybrid has all of the great features that you would want from...
A Buyer’s Guide to the 2012 Chevrolet Avalanche
Few Few vehicles are as distinctive as the Chevrolet Avalanche. Part SUV, part truck, the Avalanche is actually surprisingly practical. On the inside, it feels more like a Chevy Tahoe, except when you look out your rearview mirror, you’ll notice...
The Best Used Cars to Buy for Senior Citizens
Everyone Everyone needs a way to get around. You need to get groceries, get to doctors’ appointments, visit with family and more. However, senior citizens have very different needs when it comes to buying a used car than other demographics....