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Discussion Starter · #1 ·
Newbie hear - I hope all owners are well.

I purchased my Focus ST Estate 2012 in August 2020. I love it and it has had a Mountune map if that's the right phrase. I didn't actually buy if for that reason, it just looked lovely!

Anyway, in November 2020, the temperature gauge "kept maxing up" to the red, but would quickly return to it's normal middle position. I took it to my local garage. He suggested replacing the expansion tank? and hoses and fitting a new temp heating sensor. All was well. I never actually knew if the car was actually overheating, or it was sensor related. I did notice that the "inside heating" would sometimes kick out cold air, even when the car was well warmed up, but a few big right foot revs would resolve that issue!

In August 2021, the same problem returned in terms of the temp gauge saying the car was overheating. I took it back to the same garage and they replaced and fitted yet another heat/temp sensor. The car by the way, has always driven perfect and loses no power whatsoever.

21st November 2021 - the car temperature gauge is rocking up and down into the red...it's happening again!!!, As it's getting chilly, I have also noticed that the heating system is intermittently kicking out cold air, which resembles what happened in November 2020.

Please help!

Tomo
 

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2018 ST1 Magnetic Gray
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433 Posts
Is the car going on limp mode?
 

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Just a wild guess, but I share the same suspicion that there is potentially air in the system. Does the car ever smell hot?
It's almost like the sensor is living in an air pocket that only sometimes gets enough water to pickup a temp read, and that read is hot. It would also explain the heater behavior.
At the same time, I would think you would be smelling it if things were running that hot.
 

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Discussion Starter · #6 ·
Just a wild guess, but I share the same suspicion that there is potentially air in the system. Does the car ever smell hot?
It's almost like the sensor is living in an air pocket that only sometimes gets enough water to pickup a temp read, and that read is hot. It would also explain the heater behavior.
At the same time, I would think you would be smelling it if things were running that hot.
Interesting. Thanks mate for the possible diagnosis..
 

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Start with bleeding air out the coolant.
 

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2015 Ford Focus ST
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537 Posts
Seems fairly easy to burp air.
 

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2018 ST1 Magnetic Gray
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433 Posts
If it doesn't go on limp mode. The ECU is not getting the hot engine signal. Makes me think is a wiring related issue on the gauge side.
 
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