Engine Coolant temperature sensor at maximum

Maintenance/Repairs
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1

While driving to work this morning ~10 minute drive. I notice that the engine cooling light was on and the temperature was at the maximum about 2/3 through the drive.
What steps do I take? Is it possible that engine temperature can reach this high in just 10 minutes of light driving or is this just an issue with the temperature sensor itself? I am new to car repair (just bought first car 2 weeks ago) so any advice is welcome.

My current course of action:
Wait for engine to cool
Check coolant level
Turn on engine and check temperature
Touch coolant lines to see if coolant is flowing
???

2

Good ideas. What model, year and miles?

You’ve owned it 2 weeks, how much have you driven it before this happened.

1 Like
3

2011 Ford Focus. 140000km so just under 100000 miles. I have driven it just over 1000km. Mostly on the highway.

4

Was the coolant level correct . . . or did you have to add a gallon of coolant?!

Was this the first time the engine coolant temperature was that high?

Any obvious coolant leaks?

Are the electric fans even engaging?

Belt in good condition, proper tension?

Is the upper radiator hose hot, when the coolant temperature gauge is maxed out?

Does your coolant pressure cap at least appear to be in good condition . . . nothing obviously broken, no torn seal, etc.?

The radiator looks okay, no cracked plastic tank(s) . . . ?

Could be something as simple as a bad thermostat, could be as serious as a cracked block.

Please let us know what you’ve found, after going through my list of things to do

2 Likes
5

Checked the coolant. It is very low. I would definitely need to add a full gallon. I will do this and then monitor for leaks for the next while.

6

Here’s an idea . . .

Top off with water

Let the engine idle in your driveway, while you check for obvious leaks with your flashlight and perhaps a mirror

2 Likes
7

It is possible for the engine to overheat in a short period of time if the engine has a blown head gasket.

To find out if this is the case, when the engine is cold, remove the radiator cap, and fill the radiator if required. With the radiator cap off, start the engine and let it idle.

If bubbles start forming in the coolant in the radiator, that’s an indication of a blown head gasket.

Tester

1 Like
8

One gallon low on coolant can definitely cause this symptom. The cooling system is supposed to be sealed and air-tight, so for any coolant loss rate greater than about one cup in 4,000 miles, the reason needs to be discovered. If the cooling system is leaking then it won’t hold pressure correctly and that itself will cause overheating, even if the coolant is full.