Hey guys!

 

First post here! I would really appreciate it if I could get some help with regards to the engine coolant temperature. 

For reference, I drive a 2013 Fiesta with the 1.0 80ps (non turbo) engine and currently at 85600 miles (do about 20k miles a year). I am really obsessed with keeping the car in tip top shape and do as much work on it as I can. 

Recently we've had quite some cold weather in Scotland and out of curiosity, I used the hidden information menu to check the engine coolant temperature as the engine warms up from cold. I do not use the heater at all until I get 4 bars in the normal temp display. 

Sure enough, after a few minutes of driving the temperature was above 60 deg C. And it slowly but surely crept up to 90 (I leave early morning and do very light cruising at 30mph so it doesn't warm up as fast as it would in traffic). I've noticed that the second I am on a steady cruise, the temperature would not stay at 90 and it would start dropping, as low as 84-87. The second there's a bit of load it goes up again and on a quick onramp and 4-5k rpm it even jumps to 92 but then again, on a cruise, at anything under 70mph the engine coolant temp drops below 90 degrees C.

 

When I turn the heat on and cruise at 30mph, the engine coolant temp can drop lower than 80 degrees C, especially if I get off the throttle and do engine breaking. The second I put load on the engine, the temperature starts rising again back to high 80s and even 90 if I keep accelerating but then drops again when steading into a cruise. I can also feel the air coming out of the vents getting warmer (without touching the temp dial).

While stationary and the heat on and the fan on position 1, the engine coolant temp will go as low as the low 70s. 

Only when I cruise at 70mph or faster does the engine coolant temp stay bang on 90, no matter how hard I use the heater. Mind you, at 70mph the engine is spinning at 3.5k rpm and even on flat ground it sounds laboured. 

My question to you is, is this normal or is the thermostat (and there are 3 of them apparently so dunno which one) is on its way out? From my bro knowledge of car mechanics, the engine coolant temp should always be bang on at 90 degrees, regardless of using heat or engine breaking/light load etc. I am worried that as a consequence, the engine oil never reaches it's normal operating temp and don't want to damage the poor thing as it's relatively inexpensive to run and want to have it as much as possible! 

Sorry for the long post!

I've always understood that the coolant temperature is over boiling point and that is the reason it boils if you unscrew the cap too soon.   The actual boiling point is reduced as the fluid is under pressure.   The same way a pressure cooker works.

Actual coolant temperature always fluctuates, regardless of the temp guage , but the fluctuation shouldn’t be that high, I don’t know the actual characteristics of that engine particularly, but Mine is ecoboost 100ps, during these days we have winter in Egypt and the weather temperature is about 14 degrees at night and about 18 to 22 during the day, my coolant temp according to the secret menu once warmed up it fluctuates between 91 and 95, it doesn’t go under 88 any way,  during summer it can go up to 100 , where temperatures can reach as high as 42 !! Again I don’t know much about your engine, may be this is normal for you , but for my engine for sure it won’t be normal if that is the case 😊 

please note also that my fiesta is classified as “cooling pack II - for hot climate zones “ according to Ford Etis, I don’t know what does this mean actually 😂

Since it goes below 70 there might be something wrong. You didn't mention how cold it is there ? It depends on your cruising speed and gear (revs) and how much do you heat inside of the car.

I've got a 125bhp 1.0 Ecoboost Fiesta and now when it's -28 degrees celcius in Finland coolant temp sometimes drops below 60 degrees when I turn on the heating to max inside car. And even when I drive 80km/h with 5 gear it can drop below 60. That's why I often use 4th gear when it's this cold to keep the cars temp in normal level. On summer the coolant temp is usually close to 87-90 degrees of celcius.

On 1/15/2021 at 7:30 PM, Eng_Ahmad1986 said:

Actual coolant temperature always fluctuates, regardless of the temp guage , but the fluctuation shouldn’t be that high, I don’t know the actual characteristics of that engine particularly, but Mine is ecoboost 100ps, during these days we have winter in Egypt and the weather temperature is about 14 degrees at night and about 18 to 22 during the day, my coolant temp according to the secret menu once warmed up it fluctuates between 91 and 95, it doesn’t go under 88 any way,  during summer it can go up to 100 , where temperatures can reach as high as 42 !! Again I don’t know much about your engine, may be this is normal for you , but for my engine for sure it won’t be normal if that is the case 😊 

please note also that my fiesta is classified as “cooling pack II - for hot climate zones “ according to Ford Etis, I don’t know what does this mean actually 😂

Thanks for the reply man! I presume in that hot climate the cooling system is slightly different (maybe different type of coolant and thermostats that open sooner. 

13 hours ago, Jeipii said:

Since it goes below 70 there might be something wrong. You didn't mention how cold it is there ? It depends on your cruising speed and gear (revs) and how much do you heat inside of the car.

I've got a 125bhp 1.0 Ecoboost Fiesta and now when it's -28 degrees celcius in Finland coolant temp sometimes drops below 60 degrees when I turn on the heating to max inside car. And even when I drive 80km/h with 5 gear it can drop below 60. That's why I often use 4th gear when it's this cold to keep the cars temp in normal level. On summer the coolant temp is usually close to 87-90 degrees of celcius.

Thanks for the reply mate. Geez that is very cold indeed. The coldest I've seen here was -8. It goes below 70 when going downhill and doing engine breaking with the heat on. The second I accelerate it goes up. If I keep the heat on with the fan on position 1 or 2 at 30mph and 4th gear (2k rpm) the temp stays around 87 degrees. 

In the service manual for this particular engine Ford advises changing the thermostat only when the engine coolant temp doesn't get above 70 degrees when using between 40 and 70% throttle at cruising speed. They also say that the the temperature will go down once cooler coolant enters the engine, when the thermostat opens. I will see what the dealer says soon as it's time for the annual inspection anyways! But given the cold weather I think this type of behaviour is within the parameters set by Ford. 

 

Thanks everyone for the replies!

Just a quick update for anyone that visits this and/or is experiencing similar issues. 

 

I spoke to the local service manager at a Ford dealership and they said that what I described above is within the engine's parameters. If the engine coolant doesn't heat up at all after a long drive, that's when the thermostat is not working ok. 

 

Thanks again to all who commented!