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Old 02-29-2016, 12:29 AM   #1
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CHT vs ECT normal values? 2004 Focus 2.3L PZEV

I was running FORScan during a test drive after McGyver'ing my cyl#4 coil connector to make it stay on, and noticed something odd.

As I was sitting in the parking lot, idling, while I was looking at the misfire data and saving the live feed to disk, I noticed my cylinder head temp and engine coolant temps both inching upward. CHT had started off around 112C when I pulled in to the lot, and slowly climbed to above 120C when I started noticing, and ECT to above 101C. Eventually I noticed the temp gauge on the instrument cluster was moving, too, approaching the red. By that point, CHT was 128 or 129, and ECT was 109. I quickly shut off the car.

After finishing saving my data, I changed the monitors to include the fans, and drove home, then idled in the driveway and watched temps and fans. While idling, low fan was ON, with no fault code, and temps rose just as they had in the parking lot. Once the CHT got above 123C or so, the temp gauge on the instrument cluster started rising, too. At CHT 129C/ECT 109C, high fan came ON and low fan turned OFF, both with no fault codes, and the temperature promptly plummeted to below 110C for CHT and below 100C for ECT.

I've never noticed the temp gauge climbing like that at idle, but to be honest, usually when I'm idling that long I'm taking a nap and trying not to drain the battery as I listen to the radio or run the AC, so I'm not even looking at the instrument cluster. And the needle is not moving for very long, before it drops back down to the middle again.

Questions:
1. Are these temperature ranges normal during idle? Is it normal for temp to get so high at idle, despite low fan running?
2. Might something be wrong with low fan speed, even if there is no fault code?
3. Is it normal for CHT to be so different from ECT? We're looking at up to 20 degrees celcius (36 degrees farenheit) of difference between them. If it's not normal, what might be a cause?

Thanks,

Rebeccah



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Old 02-29-2016, 01:48 PM   #2
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Strange. Those temps & your description of system performance is different than my car; and we have the same car; 2004 2.3 PZEV. Seems like you have a cooling system problem and this might be associated to radiator inefficiency; dirty fins (?).

I do not have ECT (AFAIK) and believe ECT is only available if your car is equipped with a T-Stat housing "with Sensor". My car does not have the "with sensor" T-stat, and there is no wiring on the engine for it either.

Not saying your scan tool or software is wrong, but would help if you also use a standard measurement tool-> the odometer test mode. Temps (CHT) measured with the odometer test mode allows you and I to compare "apples to apples". Use the info found at Post-8 in the link below.

2.3 Thermostat, can I just get the 'stat itself?

Also, when testing & measuring temps, keep the AC off.

Here is one summary of system performance; when using odometer test mode as the measurement tool...

At 111C t-stat opens and cools the system back down. Radiator fans never turn on. This ONLY works if the outside weather temps are cool/cold. This is shown in post-8, link above.

At 112C-113C radiator fans turn-on low speed and cools the system back down & fans turn off. This cycle repeats in a loop. In most/all conditions, fans never engage High speed.

If low-speed fans fail to cool the system, fans will turn-on High speed if temps hit about 118C-120C.

If not using the odometer test mode, and measuring with a scan tool/OBD data instead, my test results showed temps will be 5 to 8 degrees colder.

If using odometer test mode; temps greater than 120C is very hot and should be avoided (like you did, turning the engine off).

If using scan tool/OBD data; temps greater than 120C is even hotter and should be avoided (like you did, turning the engine off).

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Old 03-03-2016, 12:02 AM   #3
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Well, I can't seem to reproduce it now. Not in odometer test mode (ECT flat at 103C), and not just sitting and idling and watching the temp gauge.

I don't know where ETC is measured - perhaps not at the thermostat, if there is no sensor in the housing. But it's an item on the odometer test mode, so there's got to be a sensor somewhere.


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Old 03-03-2016, 03:21 AM   #4
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Quote:
Originally Posted by rprastein View Post
...But it's an item on the odometer test mode, so there's got to be a sensor somewhere...
ECT is not an item on my odometer test mode IIRC. The odometer test mode displays CHT (in Celsius) and no other coolant temps/sensors are available ((are there?)). Would be nice to confirm that yours does this/has this; T-stat housing "with sensor" seems to be rare or non-existent .... <can not remember any atm, and am dead tired>.

Here is a link to someone who described each button step-thru in Test Mode in our car; should be the same in your & my car, not sure. See post-5 in link below.

Low temperature heater output
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Old 03-04-2016, 03:29 PM   #5
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Quote:
Originally Posted by Marde View Post
ECT is not an item on my odometer test mode IIRC. The odometer test mode displays CHT (in Celsius) and no other coolant temps/sensors are available ((are there?)). Would be nice to confirm that yours does this/has this; T-stat housing "with sensor" seems to be rare or non-existent .... <can not remember any atm, and am dead tired>.

Here is a link to someone who described each button step-thru in Test Mode in our car; should be the same in your & my car, not sure. See post-5 in link below.

Low temperature heater output
Post #5 in the link you posted lists Engine Coolant Temperature, not Cylinder Head Temperature, as item #11. So do other posts I have found that list the odometer self-test items.

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Old 03-04-2016, 03:47 PM   #6
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Hmm. OK, despite all of those posts referring to it as an engine coolant temperature in the odometer test mode, I can't find any references online to a Ford Focus engine coolant temperature sensor that is not the cylinder head temperature sensor. So I don't know WTF FORScan is measuring with two different PIDs, or why the engine was coming perilously close to overheating at idle when I had it hooked up that day.

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Old 03-04-2016, 03:56 PM   #7
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Some interesting information about the Ford Cylinder Head Temp sensor:
Diagnosing Ford?s Cylinder Head Temperature (CHT) Sensor

It seems bad O2 sensor or splice #127 can produce wacky CHT readings. Food for thought.
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Old 03-04-2016, 06:20 PM   #8
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Yeah, sorry about that, the linked info (at post-4) does say "engine coolant temperature" but was not meant to imply an ECT Sensor is on my/your/his/her car.

The linked article you provided (at post-7) had these comments;

“On applications that do not use an engine coolant temperature (ECT) sensor, the CHT sensor is used to determine the engine coolant temperature."

"(CHT) is used to infer coolant temperature".

Those two quotes above describe and apply to our car UNLESS the car is equipped with a T-Stat Housing with Sensor; a car with this sensor (and wiring/PCM to support it) likely has ECT (PID) data to extract from the OBD data-stream. I do not remember any confirmation of a MK1/MK2 Focus with that sensor, but I do remember some discussion about "with sensor" verses "no sensor" t-stat housings.

Quote:
Originally Posted by rprastein View Post
...So I don't know WTF FORScan is measuring with two different PIDs,...
I have seen other scan tools do similar in error. Some PIDS are available, and meant for a different car/engine type, and have no data, so dead. Other PIDS are alive yet the data is invalid because of a bad digital map/serial addressing. Some PIDS should be alive, but are dead. Several scan tools & software allow PIDS to be edited, so you can change the serial address.

EDIT: No reason to worry about or edit your FORScan PID for ECT because the car does not have it. Using the odometer test mode makes things easy to compare your/mine/others engine temp performance (CHT) when problems arise. I'm not saying that using scan tools is wrong or bad at all, but the odometer test mode keeps us on the same ball field. ->Ref discussion earlier & linked above about slight temp number differences between the two measurement tools.
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Old 03-04-2016, 11:32 PM   #9
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Depending on what ECU code you have the temps for the fans to turn on is 218-220F low speed and 220-228F high speed fans

218F is the lowest I have seen for low speed fan to come on and some duratec turn on both low and high speed at 218F

Tom
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Old 03-05-2016, 12:30 AM   #10
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Thanks, Marde.

It's a bit of a struggle for someone who isn't a mechanic and doesn't rebuild engines or do mods in her spare time. I'm still trying to troubleshoot this damn intermittent misfire on cylinders 1 and 4. I had hoped that monitoring with the FORScan software would help track down the cause, but a) I didn't get any DTCs on the test drive b) I don't know what PIDs to monitor c) the FORSCan admin seems to think DTCs should be enough (in which case I don't need this software anyway), but all I've got is the misfire codes - no lean codes, no sensor codes. Nothing helpful.

The temperature thing was just something that came up while I was sitting in the parking lot trying to figure out the software.

I had really hoped that my tweak to the coil connector would do the trick, especially since I got no codes in an hour and a half of driving afterwards, but no. Back again the next day, and today I had to stop 4 times on the way to work.

Rebeccah
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