Hi All,

I have a very strange problem in a ford c max 2009 duratec 1.8 petrol car. When I do a cold start:

1. The temperature gauge on the instrument cluster does not move until I press accelerator pedal at least once
2. The moment I press the pedal the gauge will start moving about 15c per every 5 seconds 
3. The needle will stop just before the half mark (as it should) and never moves after that
4. When I used forscan to check the ECT sensor reading it is showing about 50C when the gaugle is showing 95C
5. I took live data and it seems the car take about 15 minutes of driving to reach 90C as per the ECT sensor data

*there is no coolant loss or any sync of overheat.

Hope I did not confuse you so far. My questions:

1. How come the gauge shows one value and the sensor shows something so different. Does the gauge takes temperature reading from some other way?
2. What is the usual operating temperature for the ECT sensor?
3. How long does it usually take to bring the car to operating temperatures? 
4. Any suggestions on what could cause this?

FYI - the car seems to be running a bit rich. e.g. sometimes when I press the accelerator pedal RPM will go down a bit before it increases. This does not happen all the time.

Thank you for reading. 

The gauge does not display a live reading.  It is designed to sit in the middle over a wide range of acceptable temperatures.  It's meant to stop drivers worrying about perfectly normal temp fluctuations over a drive.

15 minutes sounds a bit slow for a 1.8 petrol warmup in 30c ambient heat.  The stat is likely to be leaking a little.

56 minutes ago, TomsFocus said:

The gauge does not display a live reading.  It is designed to sit in the middle over a wide range of acceptable temperatures.  It's meant to stop drivers worrying about perfectly normal temp fluctuations over a drive.

15 minutes sounds a bit slow for a 1.8 petrol warmup in 30c ambient heat.  The stat is likely to be leaking a little.

Thank you for the quick reply. That makes a lot of sense. Can the thermostat be cleaned? Or should it be replaced. 

2 minutes ago, samsam2 said:

Thank you for the quick reply. That makes a lot of sense. Can the thermostat be cleaned? Or should it be replaced. 

It'll need to be replaced if it is leaking.  They don't cost much on this engine, but can be awkward to access.  Fitted on the left hand side (when viewed from the front) about half way up the engine block.

26 minutes ago, TomsFocus said:

It'll need to be replaced if it is leaking.  They don't cost much on this engine, but can be awkward to access.  Fitted on the left hand side (when viewed from the front) about half way up the engine block.

Thank you. But it does not leak at all. Coolant level does not change. Unless it’s stuck open or something. Also what should be the operating temperature for this type of engine. It seems it does not go above 90c.

2 minutes ago, samsam2 said:

Thank you. But it does not leak at all. Coolant level does not change. Unless it’s stuck open or something. Also what should be the operating temperature for this type of engine. It seems it does not go above 90c.

Yes, I meant an internal leak, stuck open is probably a better way to word it.  Although sometimes the seals can fail around the edge even when the stat itself is closed.

It's an 89c stat on these so they should sit around 90c.  The low speed fan cuts in around 95c iirc.

23 minutes ago, TomsFocus said:

Yes, I meant an internal leak, stuck open is probably a better way to word it.  Although sometimes the seals can fail around the edge even when the stat itself is closed.

It's an 89c stat on these so they should sit around 90c.  The low speed fan cuts in around 95c iirc.

Thank you for all the support.