MK7 2.4 RWD Overheating

[Lukeydookeydoo]

I am a recent new owner of a Ford Transit and it has been running well with no issues until I took it to the coast and had to drive up some large hills. At this point, it would suddenly overheat with the coolant gauge climbing to 120 degrees and trigger limp mode. I would then stop for 20-30 seconds and could watch the needle descend back to 60 degrees before proceeding without problem until another hill. On arrival at a carpark, I popped the bonnet and it didn't seem to be hot. Coolant was just over max. Heater was blowing hot when used. I then downloaded Forscan and checked the coolant reading on idle and it was fine.

I have read lots of posts similar on this site and it seems that some issues could be the water pump and others have said the coolant sensor in the head. Can anyone advise which of the two it would most likely be? And how to test them without replacement?

[T350camper]

There's a few basic things you can check first. I'm assuming that there has been no loss of coolant after that run. Also if the heater was working and blowing hot then it suggests that the water pump is working (not a cast iron guarantee) and if it cooled back down again correctly and remained so when driving under a lighter load, it would imply that the temperature sensor is okay. If the fan coupling is not working correctly then the cooling fan will not be spinning sufficiently to cool the radiator under load. You need to check how still if was when hot. First by observing it running (you should be able to feel the rush of air when revved a bit...don't stick your hand too near the fan!). Secondly when the engine is turned off the fan should have some resistance to turn. Also consider that the thermostat may not be fully opening. It may work enough for lighter loads.

You can help the engine temperature in these circumstances by putting the heater onto the hottest setting and the interior fan on max speed. This will make it uncomfortable for you (open the window) but will draw heat away from the engine.

Well that's my two-penneth. Some very knowledgeable gentlemen on here who will probably have more model specific advice for you.

[Lukeydookeydoo]

I've looked but I couldn't find any solid posts about a bad thermostat doing this - I saw some stuck open, but is it the case it could overheat so rapidly if it is stuck closed. It heats and cools (on the dashboard gauge) so quickly I'm struggling to think it can be accurate but I haven't had a chance to data log it on hills etc. to replicate it.

[T350camper]

Waxstats can sometimes do odd things. One of my old cars (not a transit...but nevertheless) would run perfectly and not overheat even in town. On the motorway at 70 the temp would rise a bit above norm but climbing hills would see it rise even more. It would return to normal when the load lessened. Long story short, the thermostat was still working to a degree but only opening a fraction of what it should have. New thermostat fixed it. I'm not saying this is what is wrong with your van...just don't rule it out.

Is the fan coupling working correctly?

[Lukeydookeydoo]

I'm going to test it this afternoon. Thank you for your help

[tranmx2]

As previous.

Also get a test kit - exhaust gas in coolant.
Not expensive.

[Lukeydookeydoo]

I've left it with the garage I got it from. They are going to start with the thermostat and work from there. I data logged it and the voltage for the cylinder heat temp sensor went from 3v to 1v gradually and then did a jump to 4v and went up gradually from there. Is that normal behaviour?

[Burn2]

Hello.

Take a look there:
viewtopic.php?f=5&t=223399
Could be the same pb.

But first change calorstat+ coolant + pressure cap is the first things to do if it's old.
Then take a drive with forscan and read temp. Gauge always jump in one time so does not show anything.

[Lukeydookeydoo]

Hello.

Take a look there:
viewtopic.php?f=5&t=223399
Could be the same pb.

But first change calorstat+ coolant + pressure cap is the first things to do if it's old.
Then take a drive with forscan and read temp. Gauge always jump in one time so does not show anything.

Thanks - the thermostat should be changed today. I read through - did yours turn out to be the fan?

[Burn2]

Yes.
In my case the problem was the viscous fan ( no electric fan on mine ).

[knobby1]

Hello.

Take a look there:
viewtopic.php?f=5&t=223399
Could be the same pb.

But first change calorstat+ coolant + pressure cap is the first things to do if it's old.
Then take a drive with forscan and read temp. Gauge always jump in one time so does not show anything.

Thanks - the thermostat should be changed today. I read through - did yours turn out to be the fan?

I'd be checking/changing the CHT sensor, they can and do play up causing the symptoms you have....guage rising and falling relatively quickly and indicating overheating but the engine itself is not that hot.

Lord Knobrot

[Burn2]

Yep clearly if it jump and goes back to 60° fast it should be cht sensor.

Read live data with forscan would easly confirm that.

[Burn2]

I add more explanation.

As i said, the gauge could jump from the "normal" middle position (that is to say near 90°) to 115° in one second, that was my case.

Just to refresh the memory, on the 2.4 tdci, there is only a CHT sensor, no ECT/EOT sensor. it calculate from CHT sensor. (for ECT it seems it based on the difference between 2 cht value + it's temp. So it follow it with time)
The gauge on the panel will move when ECT sensor calculated increase to 115°. If you are in 113° calculated, it will be in the middle... So you could not see if it's hot before.
At 120° ECT it will go to the maximum right position.
When CHT sensor is at 132°, engine cut off in security mode with overheat led.

But in that case, the gauge will jump from 90 to 115, and back to the middle center position (90) in a short time if it's limit (or increase to the 120 position), not to the cold position of 60° that you could only see when engine is cold.

If it's really see the gauge going done to 60 after going to 115° with a really short time, then the CHT should have a problem or there is air in the cooling system. (that's why it's often advice to change the pressure cap to be sure there is no problem)
But as said previously, it's better to take real CHT value from forscan to see what happen really before and after.

For the voltage, the CHT if i am not wrong it's 2 sensor in it, one for low temp, and one for hot temp, and there is case where cold temp where ok, and hot temp where wrong, with hot temp jump then goes back etc. In the voltage if i remember well there is two range, so there is a jump between the range (so when it switch for the hight temp) but after that the value should not jump.
Here is a post that explain how cht work on the 2.4:

I am attaching a translation of a fragment of the Ford manual regarding the CHT sensor. I hope google translate made it understandable...


CHT sensor (CHT = Cylinder Head Temperature) replaces ECT sensor and temperature sensor transmitting information to the temperature indicator in the instrument cluster.
The CHT sensor is screwed into the cylinder head i measures material temperature instead of temperature coolant.
Thanks to this, if the engine overheats (e.g loss of coolant) is possible more accurate temperature measurement.
Note: Every time the sensor is removed CHT should be replaced and tightened to the recommended one moment. Otherwise it could damage to the sensor (e.g. distortion ends).
My note: it is good to use white ceramic paste when assembling the CHT.

The CHT sensor is a thermistor, i.e. a negative resistor temperature coefficient (NTC resistor).
The output signal is an analog voltage signal, which is inversely proportional to temperature material from which the head is made cylinders and directly proportional to the resistance.
The voltage signal is processed in analog to digital signal converter digital and then it is sent to the microprocessor in the form of numerical values (counts) that the microprocessor assigns appropriate temperature values.
The resolution of the CHT sensor is not enough large at high temperatures to measure temperature in the entire range from -40 °C to +214 °C. Therefore, by including the second resistor in the PCM module characteristics


The first curve is in the temperature range material from –40 °C to approx. +78 °C. transistor in PCM module turns on a second resistor called pull up resistor to extend the range sensor. Second temperature curve of the material ranges from about 62 °C up to 214 °C.
Example: Sensor output voltage of 2.5 V (= 500 Counts) can mean temperature material 35 °C and 124 °C (see diagram), w depending on which curve you get assigned voltage value. After turning on
the resistor "pull up" the microprocessor assigns the numeric value "500 Counts" of the second curve.
This means that the temperature of the material is at higher range (in this case 129 °C).
Application of CHT sensor signal:
• Fuel dose
• Start of injection
• Idle speed
• Glow plug control
• EGR system
• Temperature indicator and lamp control
glow plug indicator light
Symptoms in the event of a fault
Open circuit:
• In the case of an open circuit, the circuit accepts maximum temperature value of 120 °C.
• In this case, the fan(s). the radiator and the engine run constantly at reduced power (reduced fuel dose).
Short circuit:
• In the event of a short circuit, the system assumes a value temperatures > 132 °C.
• In this case, the engine stalls or fails run it.
In the event of a faulty sensor or engine overheating protection function is activated engine overheating.
In this mode, engine power is reduced by injecting less fuel. If engine temperature continues to rise, depending
From the vehicle version, the engine power is more and more reduced.
Note: To avoid engine damage engine cannot be started at temperature cylinder head below –35 °C. The reason of this there are large doses of fuel that in such a situation could cause damage. In vehicles for cold countries, special ones are used strategies or devices for engine heating.
Diagnostics
The monitoring system checks:
• sensor for short to ground/battery
and open circuit.
• sensor for illogical jumps
voltage (illogical voltage spikes may be
e.g. loose contact).
• signal at an angle
-----------------------------------



Description of drawings:
1. ------
A Digital signals (counts)
B Voltage (V)
C Material temperature sensor
1 First curve
2 Pull up resistor switch point
3 Second curve.


2.-------
1 PCM
2 Second resistor ("Pull up")
3 First resistor
4 CHT sensor (NTC)
5 Sensor output signal
6 Analog-to-digital converter
7 Microprocessor
8 For comparison: ECT sensor

[Lukeydookeydoo]

I'm learning so much about transits and I'd only owned it for a month!

Got it back with a new thermostat and ran the heaters - they seemed to be proper hot by the time I drove home (2 miles). Although the water-fed rear fan heater in the rear (it's a minibus) remained cold. I wonder if it's on a different circuit with some form of blockage in between. I didn't datalog it on the way home but did letting it idle after the run and it stayed 92-93 degrees CHT. All pipes from the stat were hot but I noticed after I turned the engine off and opened the bonnet that the bottom rad pipe was room temp and the top was hot. Is that normal?

Checks I'm going to do in order:
Expansion tank cap.
Cooling fan.
Radiator.
Head gasket.
CHT sensor (as it seems to be doing the job).

Sound like a plan?

[metalworker0]

AIRLOCK - it may be impossible to get an air lock out without a vacuum coolant bleeder device ...its also possible that there is a bleeder valve at the highest point near the rear heater core.

all the best.mark