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A Car's Temperature Gauge
by
Mike Florence & Rob Blumer
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- Usually, a car's temperature stays the same
- A faulty thermostat can show a low temperature
- Air in the system can cause temperature surges
Related Articles: A Car's Oil Pressure Gauge | Basic Antifreeze/Coolant Maintenance
Depending on the car, you may notice very minor fluctuations in the position of the temperature needle after the car reaches its optimal operating temperature. Generally, though, it remains in a nearly still position once the car has warmed up.
Think about all the things you know about the cooling system—about radiator pressure caps, pinhole leaks, the cooling fan, a dirty engine hampering proper cooling. Should the needle on your car’s engine (or coolant) temperature gauge begin to rise, or find a new higher temperature in the “norm” range, that gauge is telling you something.
Go through a mental checklist: A pinhole leak may have been drawing off coolant in imperceptible amounts for weeks, so there is less coolant trying to do the same job as before; the cooling fan may not be coming on at a traffic stop, causing the needle to rise, then returning to its usual position once the car is at speed again; the coolant you never changed has created corrosion in the radiator. The list can go on, but the point is, that temperature indicator is yielding valuable info you can use to keep your car from a distressing and probably damaging situation.
A needle to the lower side also yields useful info. Right off, you know that your car is not achieving the hot optimal temperature it requires for maximum efficiency. Can you guess the most likely culprit? Anytime a gauge or idiot light gives its warning or fluctuates, it may wind up being a problem with the sensor (the sending unit) itself, but always trust your instruments first. Okay, the most likely cause of a lower-than-usual temperature reading is a faulty thermostat. Change it.
A coolant temperature gauge may help diagnose a cracked head or worn head gasket early enough to prevent engine damage. If driving down the road, you notice the temperature gauge jump toward hot then drop back to normal, and repeat this cycle, it may be telling you that a head is cracked or the head gasket is worn and leaking.
The sudden jump in temperature, and the equally sudden return to normal, is a good indication that air has gotten into the system. The sudden temperature surge is caused when a pocket of super-hot steam envelops the temperature-sending unit. The temperature gauge returns to normal when coolant chases away the pocket of steam.
…from The Everything Car Care Book. For more books, visit Adams Media Bookstore.
Related Articles: A Car's Oil Pressure Gauge | Basic Antifreeze/Coolant Maintenance
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