Temp sensor

[Morgy1]

Hi all, i have a 2006 1.4 petrol fiesta. I noticed the engine fan is not working and the coolant is coming out of the expansion tank cap when warm. The temp gauge says 4 bars. If i disconnect the engine temp sensor the fan runs. I fitted a new sensor and the car runs for a couple of seconds and cuts out with the following fault codes. Again if i disconnect temp sensor she starts and runs fine but red temp on dash. Any help gratfully received

 

[Handy Andy]

Since this is an older car, does the instrument cluster / Pods / HEC unit - has it's wiring been checked?

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Since you get "4 bars" - one sender seems to be working - another which is the overheat one that engages a fan, as you found out - seems the wiring is functional to it, but the wiring to the display - thru the instrument panel - might not be all there.

Now what I also see is a "ignition failure" - a wire from the key ignition seems to have failed - was someone trying to hot wire this car - the wiring is not completely fixed. This wire may be the one that causes this fault because of the broken connection.

In doing further research, the communication via data network - is what seems to be causing this issue - so the CAN Bus system, the one that works like a USB stick and cables - is down or has lack of connections to relay information to a specific section that the vehicle needs to verify its integrity.

IF it can't communicate to store and compare data - it sets this code.

 

[Morgy1]

Thanks for your reply Handy andy. As for the hotwiring i dont know as ive only had the car a short while. I bought it in need of a clutch for my sons first car, fitted clutch but have not used the car. It is now i have come across this problem. As for the wiring being checked i have not. I have only checked the multiplug behind the batery for corrosion but all seems fine. Could you point me towards the wiring that needs to be checked .
Many thanks

 

[Handy Andy]

This requires a set of torx bits - a small eyeglass screwdriver - and a lot of patience.

Because you'll have to take apart the steering column to get at the pod display and remove the assembly and the column cover so you can find the connectors that work the ignition switch (or Push to Start) and the communications that head off to the display console and a head unit under and inside the dash.

Right now, as it stands, that "wire" the primary or top code is showing you - just might mean the code that is set when you forget to turn the key to ON - not Start, but ON - (ignition) so it can communicate to the system and check CAN bus.

As of now, there are two temp sensors one on the backside of the motor - by where the ignition coil plug sits, its' under that.

IF that is the one you changed, then the wiring from it is suspect.

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It is a 2-wire connector - one is variable - the other is power - so you'll have to investigate the reason for that failure - more than likely - when the Fan comes on, it's due to the connector not seating right. The thing uses a "grommet" that when that seal fails - they expand and are designed for that - but once allowed to be opened, they are extremely hard to reseat.

To Help, was a "Idle Relearn procedure" done?

Another: The original Fiesta from those years uses analog gauges.

The battery needs to be pulled and if the sender is the correct one for the year - then the "out of range" is due to the now new sender needing to be re-zeroed - if you've already done this - then hope you kept the old sender because you'll need to look at both to determine if the connectors are correctly sending the range of variable they need to.

So, you should do a continuity check make sure the wiring at the connector side - is not damaged from being yanked out.

 

[Morgy1]

Ok outed the new ebay coolant sensor. Bought one from local motor factors. Everything is now back to the beggining, car starts runs fine no lights on dash, BUT still no radiator fan working and coolant getting to boil out of header tank. Temp gauge does not go over half way any body any suggestions

Ps have read that if thermostat not working correctly the engine can overheat and fan won't kick in
Any thoughts ?

 

[Handy Andy]

Since yours is the 1.4 Petrol, have to checked the FAN housing? There may be something there...

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You may need to verify that the Low-Speed Resistor and its thermostat is in there and functioning - else I'd recommend you try another housing.

 

[Morgy1]

Mine is just 2 pin connector, fan works fine when you pull plug from temp sensor.

 

[Handy Andy]

Then, then the Fan is off - does that power connector to the FAN connector itself - have 12V all the time?

Reason is this, and read this thread
https://www.fordfiesta.org/threads/st150-radiator-fan-not-engaging.8907/#post-24264

Because it may apply to your situation as a controller in the Fan shroud itself or in the harness to the fuse box that retrieves power from the car, to power a Dropping Resistor inside it, that runs based upon outside temp and the temp of the air blowing thru the unit - only that when the TYPE of Purpose of Relay kicks on - the resistor is used or its' bypassed - because the SELECTED Purposed Relay back at the Power Fusebox - overrides it.

The link to the Thread above is to help you know that there are some cooling systems that use two speed fan systems based upon the BCM's thoughts (if it be the word) that it needs the Fan on due to engine temp and outside air temp are too close to a predicted condition that if the Fan does not run, engine damage can occur if the engine demand is too great - for several reasons that the engines cooling capacity in the engine jacket itself is small and the thermostat should be opened enough to circulate coolant all the time to reduce the boiling that can occur inside the motor because of the greater demand - reduces weight and fluid - so the capacity is smaller but is in demand to be used when these conditions of temperature occur.

You may have a Low-Speed Relay and the High-Speed Relay. The Fan kicks on when the High-Speed relay works because it can't' read data from the temperature sensor you disconnected. So, the High speed then clicks on and runs - when you think you did have the Fan running at other times more than this, then it (your Memory) should be a good clue as to the existence of a Low-Speed Relay or another Relay used for the Fan is not working and now the engine gets too hot too quickly.

So you have two things to research. An Air Temperature sensor unit and the possibility of a second temperature sender unit - most likely by the Thermostat housing - need to be verified.

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To Help:​

1. You already know that you get "4 bars" so if you have the digital dash or the Analog Gauges - either way - you have something sending the information to you thru the dashboard.
2. Did you verify that all the Radiator system support functions are working?
   1. Radiator free of debris, but is the Radiator shutter system working - or are you aware of it? Not All Fords use this shutter to help with speedily heating up the vehicle's engine for better fuel efficiency. Best to check - as many do and as they age, they tend to hang in a position of lesser airflow (partially open or closed) reducing the airflow at low speeds, but they work fine at highway conditions because there is enough airflow thru the radiator at those speeds
   2. Relay back at the Fuseblock in the engine compartment - all those Relays working?
   3. A/C system, this is where the Low-Speed and High-Speed systems tend to show how they work.
      1. Low Speed Fan may click on and the Fan is whisper quiet until the AC compressor kicks in, then that fan roars to life.
   4. Wiring - this vehicle is pretty old, so the grounds to the Fans and any electrical systems - they need good connections, so the issue becomes self-explanatory - the Fan is not working very well because much of the systems using the wiring are finding corroded connections and fail to make or work with proper contact and voltage in which to power it.
3. You'll have to figure out why the "profile" between the known values recorded and these newer values - are setting the light on the dashboard - most likely it is reminding you of your own memory of having a fan running when the engine was warmed up - only as a low-speed fan you didn't hear all the time.
4. So this new profile tells you that that either the Body Control Module is having issues, or the PCM is having problems sorting out why the engine runs so hot when it didn't before.
5. Got to find out if a Low-Speed Relay and High-Speed Relay are even used - to me I think it is, else the PCM would have ignored this input and simply ran the Fan when it got to the upper limits. So to me the PCM is trying to tell you something is not right - we may be chasing Ghosts, but the effort still remains that the PCM and the BCM need to agree else the light on the Dash (The DTC) will simply tell you of the younger days of motors - they ran cooler.

The Owner's Manual to the 2006 is so old and outdated information - it's not very useful - except to point you to the engine compartment and to the Glove box for Fuses locations - so since it's more of a European built one than American - the issue is lack of information to direct you to the specific section to help you diagnose this.

 

[Morgy1]

Ok Andy an update. It turns out that what is happening is the fan is working but does not kick in until after the coolant spewes out of the expansion tank top. At around 103c the tanks starts spewing boiling water out of the cap the fan then kicks in at105c every time after about 20_25 seconds the temp is down to around 93c and level is back to normal in the tank. Any ideas

 

[Handy Andy]

Did you find out if the radiator has a shutter in front of it?

Can the Tank when the cap is on, show and hold pressure...?

I find it odd that this is the 2nd time that someone is having coolant boil when things otherwise appear normal.

Else the coolant is too weak to handle the temperature - it's boiling faster (at lower temperatures) than it should.

105C is just above water boiling point (~220F) - so why the sudden boil - usually means when all other things like;

Radiator - flushed cleaned of debris
Thermostat - opens by feeling the hoses to show circulation of hot fluid is working
Hoses - intact and not leaking or otherwise showing weak walls or failure
Fan does click on - as temperature shows just above boiling
Worry point is 250F or 120C - that is when you need to worry - at least what it says (or Should) on the side panel of the coolant
Coolant itself is not dark or discolored or thickened with oily residue.

When all other obvious factors can be accounted for - the only other issue is the Coolant itself not protecting the engine because of its lower boiling point than the sensors used to see temperature to prevent the overheat - cannot do the job of protecting the motor.

Continuing to operate like this might put the Head Gasket at risk.

 

[Morgy1]

No shutter in front of radiator.
Tank boils without top on as well as with. Just to point out i am running it with just water, no coolant as i thought until i solve the problem its just throwing the coolant out of the tank and wasting it. Should i try 50% mix and see if that sorts it ?

 

[Handy Andy]

The issue of what you had in the first place in bringing you here, was not able to make the Fan run.

So what I've learned from this is the coolant temperature sending unit is working - but the Fan doesn't seem to come on like you think it should.

Ok, learning that the coolant is boiling at 105C - means the temperature sensor is not the problem - the Coolant is boiling too quickly - at a lower temperature for the sensor to tell the Fan to turn on.

IF you want a cooler temperature for the fan to kick on, I don't think the Fiesta can do that - at least by running a different sensor - it would require a programming of the PCM and or Body Control Module BCM to tell the system - hey when the temp hits here - then turn on the Fan.

IN earlier models - they had a separate circuit that would use a relay to turn on the Fan - thru a DROPPNIG resistor - one that made the fan pull air thru the radiator in less volume (a slower speed) - keeping the engine cooler for a longer duration of time - done for a different motor Ztec or even the Duratorq ones - but NOT the Sigma (Fiesta Duratec) by running the Fan longer kept the engine cooler - but would allow the Hi-Speed Fan relay to override the low-speed circuit by bypassing that circuit with the relay running the Fan directly.

Now that I know you're runnng the more diluted water as coolant - then the issue becomes clear - the fluid cannot attain a high enough temperature to tell the Sensor to operate the Fan - it will boil dry first try to keep the engine cool. The Fan is only going to operate when the system thinking is that it has the right coolant for the job and "when I get hot", the Fan then will cool me down but by only so much.

I know, with the above thinking that Ford seems to run a higher risk of engine failures due to this type of temperature profile. With my background experience and way of thinking - I would agree. But to be honest - I don't see too many options here to help reduce or improve the colling systems performance except to deal with a hot motor and the cycling of a fan that helps keep the motor at the top of this range.