I replaced a leaking plastic pipe feeding the thermostat from the top radiator hose on the Jaguar XK8. The new crossover pipe came with a new temp sensor installed. Coincidentally, I began playing with my new TORQUE Pro app. Due to a sudden cold snap I noticed that the fans stayed on more than I thought they should in 20*F weather. They always run on low speed with the AC on but continued with it off.

The TORQUE temp reading was nominally 96*C and wandered around between the 96* and the highest reading at 106*C in stop and go traffic. At the 96*C I measured the brass sensor body with an IR temperature device at 84*C, exactly the specs of the thermostat. I pulled the thermostat and did the pan-of-boiling-water test. It reliably opened to full beginning at that 84* as measured by the IR device.

I discussed with the Coventry West and they instantly agreed to send me a new pipe/sensor. Both original and replacement had the correct OEM sensors. Installed replacement and am getting exactly the same symptoms. Fans still run more than I think they should. That seems the only issue although I would suspect that the Engine Control Module is going to respond with fuel management somehow to a higher than expected temperature.

Has anyone seen this with the TORQUE app or installation of WhiteXKR's Real Gauge? I have a Real Gauge but just have not taken the time to install it. Guess that will give me something to do this evening.

 

I have compared my real gauge readings with my wifi OBD Reader and iphone equivalent of the Torque app, and the 2 readings were an exact match.

 

From my post on the TORQUE forum I find that the digital signal at the OBD data port is converted by a 6 (?) line PID software plug-in to the TORQUE displayed reading. I would suspect that WhiteXKR picked up that standard conversion and therefore your readings would be expected to be the same.

My issue is that the converted display does not match the reading on the IR thermometer reading of the temperature of the coolant by more than 10%.

Since every temp sensor is going to be different by some within spec percent the final displayed result should not be expected to be an absolute display of reality until calibrated by a custom conversion factor.

 

Actaully I am interested to see the RealGauge result. Yes, RealGauge is based on the coolant temperature sensor just like Torque over OBDII, but it actually is not reading OBDII data.

RealGauge uses a Pulse Width Modulated temperature signal that is transmitted from the computer in the Instrument Cluster to the Climate Control Module and is unique to the X100 and X308 Jaguars.

 

Thanks.

That excludes the Real Gauge from the OBD/TORQUE discussion. Too late, I am not going to get the RG installed this evening. Got things to do tomorrow so the XK8 DD has got to be there.

I will post back.

 

Are the thermostat and ECT in exactly the same place? (Many cars they aren't.)

Coolant at 84 C would be very low in today's cars which have to get low emissions and good MPG.

 

The ECT sensor is located in the plastic crossover pipe feeding the thermostat tower about 4 inches away. I have an 84*C/183*F thermostat installed which, I believe, is the correct OEM version.

 

Tom, see page 17 of this TSB: http://www.jagrepair.com/images/TSB/...0Diagnosis.pdf

It has a table of resistance values you can use to determine what the temperature sensor is conveying with an ohmmeter.

 

Thanks Steve!

I searched the net for an hour looking for that chart and I had it in my TSB file all the time. I suspect that the answer to my concern is not the sensor since two have now demonstrated the same results. I am going to chase the custom PID in TORQUE to 'tune' the displayed output to the IR measured coolant temp. Don't know why as I really am going to install the Real Gauge.

Something new to learn and I see the same issue with the V8 Volvo but not to the 12-14*C spread of the Jaguar.

 

I've brought my 02 xkr up to idle warmed up (in garage). I have RealGauge installed and the Torque app installed. Real Gauge runs from 125 - 245 so each quarter increment is 15 degrees, So half way is a temp of 185.
Note the coolant needle in torque is almost exactly at 185 so I'd say they are providing pretty equivalent measurements and would appear to be accurate.

 

Then why is mine 12*C off?

My calibration of the IR meter, which does not have a real calibration mode is done by measuring the temp of a spoon in a boiling pan of water. It reads about 99*C/209*F but then I am a little above sea level.