Has anyone had any issues with engine coolant temperature dropping when driving? Mine normally sits smack bang in the middle on four bars but recently it has been struggling to get to 3 bars and often drops back down to 2 even during long distance drives.  

I have a 2015 Zetec S. Any help would be appreciated. Thanks

Your thermostat may be sticking, or has failed open. What engine have you got? (Reason I ask is that the Ecoboost has more than one for different stages of the warm-up cycle)

I have the 1.0 125 ecoboost engine. Will this be cause any harm to the engine as I've not noticed any performance issues etc. ? 

If it was a thermostat it wouldn't cause any harm; you might just fine your find economy drops a bit.

Next time you are driving and the reading starts dropping try pulling over and sitting at idle. If the temperature starts to rise again then this does point to a stuck thermostat as the absence of airflow through the radiator means the symptoms of it being stuck have less/no effect.

Ahh thank you very much!!! I think what you're saying might be true as I've noticed when I'm driving in stop start traffic I have seen it remain stable at 4 bars (which is what I usually see it remain at) but any time I start my commute to work on the motorway it struggles to rise!

Would it be an easy fix to get this resolved myself? Or worth taking it back to Ford as it's still under waranty.

Be aware that the temperature shown on the temperature gauge is a calculated value. This is not a realtime value. The temperature shown on the temperature gauge is calculated by the PCM. The PCM uses data of several sensors to calculate the temperature. Every single one of these sensors can affect the temperature that is shown on the gauge.  

I have seen before that a defective sensor that is not directly related to the engine temperature caused incorrect temperature gauge readings.

In all honesty I haven't got to know the Ecoboost engine well enough yet to see what access to the thermostats are like. I'll take a look and get back to you.

I do know that the part should be cheap if this is what it is.

 

12 minutes ago, JW1982 said:

Be aware that the temperature shown on the temperature gauge is a calculated value.

Would I be right to assume that an OBD reader would give access to the raw value of (just) the engine coolant temperature sensor?

12 minutes ago, MJNewton said:

In all honesty I haven't got to know the Ecoboost engine well enough yet to see what access to the thermostats are like. I'll take a look and get back to you.

I do know that the part should be cheap if this is what it is.

 

That would be great thank you very much!! 

13 minutes ago, MJNewton said:

Would I be right to assume that an OBD reader would give access to the raw value of (just) the engine coolant temperature sensor?

A decent diagnostic system/software should indeed be able to display the realtime temperature.  

I've had a look at the engine and the access looks okay. The main thermostat is in a housing on the right-hand side of the engine but to get to it you'd need to remove the main intake hose from the filter housing to the back of the engine. You'll then see the thermostat housing, the end cap of which has a hose connected to it and the stat inside.

The engineering code looks to be CM5G 61J20-AA which translates to a part number of 1812482. I don't know what the dealer price would be for a Ford one but OEM suppliers are available e.g. here.

A Haynes manual would probably tell you to remove it, dangle it in a pan on the hob and check it starts to open at around the 92C point (it probably wouldn't fully open until above boiling point so you wouldn't be able to see this occur). For a tenner though you might want to just replace it!

4 minutes ago, JW1982 said:

A decent diagnostic system/software should indeed be able to display the realtime temperature.  

Thanks Wilco. I was more thinking even just the most basic of basic readers ought to be able to pick up the ECT value and that surely Ford would not have engineered it so that it gets a combined-calculated figure. (It would not surprise me though given that's what they've done with the dash!)

4 minutes ago, MJNewton said:

Thanks Wilco. I was more thinking even just the most basic of basic readers ought to be able to pick up the ECT value and that surely Ford would not have engineered it so that it gets a combined-calculated figure. (It would not surprise me though given that's what they've done with the dash!)

I know that accessing the Test "Secret" dash menu can show you engine temperature. Would that be more accurate that the gage? Or simply just show me the same combined value?

Here's a picture (taken from above) of the housing. The cap, with the stat inside it, is at the bottom of the picture with the large hose connector going to the left.

(Incidentally, the coolant temperature sensor is the grey connector)

When changing the thermostat it is recommended to also change the coolant. On the 1.0 ECOboost the coolant can form crystals as a result of the higher coolant temperature. These crystals can attach to the internal cooling system parts and cause problems on the long term.

When changing the thermostat the coolant system needs to be partly drained anyway so it is little effort to change the coolant completely. On this type of engine it is highly recommended to vacuum fill the coolant system. This way there will be absolutely no air in the coolant system.

10 minutes ago, causer said:

I know that accessing the Test "Secret" dash menu can show you engine temperature. Would that be more accurate that the gage? Or simply just show me the same combined value?

The test menu of the instrument cluster also shows a calculated temperature. 

Any advice on how to 'vacuum fill'? (It's not something I'm familiar with)

In which degree should the fan open in ford fiesta mk3 engine 1.4 and thanks 

Obviously if your car is under warranty you take it to Ford for a fix.

The car has a coolant temp sensor which is probably one of the main sources for calculating the engine temp reading. If you have access for infra red thermometer you can measure the plastic coolant reservoirs temp and see how high it goes. (Do not open the reservoir when engine is warm but just measure it's temp) It should be pretty high when the thermostats are working properly. Not sure how high though 🙂 I assume the coolant is running somewhere between 80-100 degrees celcius so the coolant reservoir should heat up to about the same temperature.

Also in low engine temp the coolant shouldn't circulate via the radiator. If the radiator gets warm almost immediately after you start driving your car it could mean that the thermostat is stuck open.

Here's a clip for changing the coolant temp sensor for Focus 1.0 Ecoboost engine. It's probably located in a same/very similar place in Fiesta 1.0 Ecoboost engine. 

 

On 4/23/2017 at 10:09 AM, causer said:

I know that accessing the Test "Secret" dash menu can show you engine temperature. Would that be more accurate that the gage? Or simply just show me the same combined value?

Hi did you get this sorted and what was the cause thanks