Nice day today , sunny , little breeze and 84*. So me and the bride started out on a 3 hour cruise (sounds like Gillian Island theme). I mentioned I had installed a scangauge to monitor WT and Volts. So today I did a little more tracking of the WT. I started the car and WT was at 80*F and rose at a rapid rate within a few minutes and about 2 miles. Settled out at 195*F at around 40mph. We headed over to the mountains across the river where outside temps went to 87*F. At 55 mph WT stayed at 193*F and as we crawled through traffic in a small town it went up to 203*F. We then went up the mountain following some slower cars and at 45mph hit 231*F . It spiked at one time while stopped at 215*F but was for less then 15 seconds. Going down the back side of the mountain while coasting at 55mph it actually dropped to 189*F but came back to 193*F. The rest of the drive through back country/mountain roads yielded the same with fluctuations between 193*F to 211*F. So this was an interesting exercise and makes me wonder if Jaguar didn't want to display the variation in the range. I wonder if on the F-type and the other jags that have a WT gauge if it is dampened to maintain a normal temp range. By the way the variation isn't a problem but only interesting that it floats like it does. Now for you 2010-2015 folks I might do a track on the voltages as they fluctuate with the Jaguar smart charging system. OK just some FYI

 

Back in the day I had a 54 Buick with a very good OEM instrument system. I could watch the water temp drop when I ran the heater.

That old car had back and front seat heaters on separate circuits. They could really dissipate some engine heat. It was interesting to watch. Try it on your JAG.

 

I am surprised how much the WT varies on the XK. It was 115*F here in Tucson yesterday and my XK WT got to 225*F at stoplights. I went into Home Depot for about 10 minutes. When I came out, before starting the car, it was 231*F. It quickly dropped to ~ 219*F while backing out of my parking spot.

The in dash temperature gauge on my XJ does not vary after warm up. I will watch the OBD temperature sometime and see what the temperature is really is doing.

I drove my Xterra yesterday in the 115*F heat and the OBD WT did not go over 205*F. I assume that means it has a better/higher safety margin cooling system than the Jag. No surprise there.

The OBD gauge numbers are interesting. I am not going to start worrying unless the temperature goes up over ~230*F under "normal" driving conditions. My gauge alarm is set to 225*F. I think the car's warning alert goes off in the mid 240's and the coolant will boil at a little over 250*F.

My voltage varies from 13.1 to 13.4 V. Car has a new Jaguar battery replaced in January 2017. I am interested to see if a lower voltage or wider range is an indicator of a battery in need of replacement. I will monitor the voltage of my 2013 XJ with its original battery and see what its minimum voltage and range are as I am sure it needs to be replaced soon. My guess is that the response time of the gauge is too slow to see the problems caused by a "bad" battery.

 

Yep the XJ WT gauge is just a fancy idiot light and doesn't reflect actual temp. Normal operating temp parks in the middle. It does jump up on overheat though.

I think something to consider is the accuracy of the BT dongle you're using with the your app. The output varies.
I have one dongle that shows 13.6 and the other shows 14.2 on the battery. Same app, different dongle.
Water temp range varied too.

 

On the voltage the 2006 to 2009 charging system was pretty old school and you should be seeing 14.2 V normally during your drives. The 2010-2012 will vary depending on battery condition and load/demand. Voltages will run between 12 to 14.5 based on what I understand and am seeing. If you drive with a fully charged battery it will be between 12.5 - 12.8V. This is using a wired OBDII port adapter and not a dongle.

 

Back when I had a 2004 XJR, all of the gauges, WT, Volts, Oil Pressure worked properly when I bought the car. Once when I picked up the car after a standard service (oil change, etc.). None of the three gauges would move off of the center points. When I asked the Service Manager what was going on, his response was the change was mandated by Jaguar NA and the gauge operations could not be changed back. So there you have it. Now they just give us idiot lights.

 

Hmmm, I thought the voltage measurement was done in the ECU and transmitted to the OBD reader as data with the WT and fuel trims. If the OBD reader/dongle is doing the voltage measurements then I am not sure how useful the measurements are because they are not taken at the ECU. Maybe the battery B+ does not matter much because the ECU and all the other controllers in the car will have their own power supplies and regulators.

I am not sure WHY a "bad" battery, that still cranks the car over fine, causes such havoc on the Jags. The batteries in ALL the other cars I have owned were fine until they would not crank anymore. The V8 Jags that I have owned had to have the batteries replaced long before they quit cranking.

 

Probably inadequate circuitry inside the PCM, so I suppose blame their makers (Visteon, Denso, ...) - not that it helps since we are where we are.

 

I think is a lesson on where you should downshift and get the revs up a bit. High load low RPM isn't the best for an engine and the data looks like it wasn't happy there.

 

Sorry if I wasn't clear Dave. I'd expect no change came from the ECU output the the OBD port, but, the dongle may not be reading it accurately.

As I indicated, I had two dongles, swapped them back and forth a few times on the same drive (working on an unrelated problem) and noticed the differences in the readouts.

What I didn't do is run it while connected to SDD to see which dongle was more accurate. Bottom line is that the differences weren't cause for concern. I'm just pointing out they we all may get slightly different readings depending on which chipset is in the dongle.

 

This was done by most manufacturers as repair shops would get multiple visits from concerned car owners if their gauges began fluctuating (acting normally) with varying conditions. The 'average' motorist, if they even actually pay any attention to the gauges, want to see all of them settle into a normal range and stay there. If not... Imagine the horror of seeing a real oil pressure gauge go up and down with heat and engine speed!!
We enthusiasts must resign ourselves to dealing with the most common denominator: ignorant, uninformed car owners.

 

There is a shocking % of drivers who do see scary indications on the gauges or red flashing lights and continue driving anyway.

 

That's what electrical tape is for!

 

My old Corvette has a bright red indicator light warning that one or both headlight buckets are not in the full upright locked position. The swoop of the hood means they cannot be seen from the drivers position.


In taking the car out for a test ride prior to purchase, I noticed the warning light being on. The owner at the time pointed to the roll of electrician's tape sitting in the ashtray. I presumed it was for temporary repair of a wiring harness, he clarified that it was to cover up the annoying warning light.

 

The PO of mine said they just kept resetting the TPMS and CEL's when it popped up... Damn distracting is what it is. I have air bag, tpms and CEL on at the moment. Nothing life threatening other than the distraction. Black tape sounds easier than pulling the cluster to 'disable' the icon lights.

 

 

Jagtoes,

Do let us know if turning on the heater has any effect on water temp.

 

If I remember to do it I will but usually I just leave the system on Auto. It's set on 70*F so I'll have to force it do heat .

 

1. Do you think it would be useful to use a handheld IR thermometer on the radiator hose to the right (passenger side) of the outlet tube, to determine the coolant temp before it enters the radiator? That would help to confirm or deny the temp readouts provided by your aftermarket gauge.

2. Is it possible that the thermostat is not fully opening, and needs to be replaced? I recognize the XKR has a metal outlet tube vs. XK which has plastic. In the case of my 2007 XK, one of the two tabs holding the original thermostat to the cover had broken, and it appears the thermostat would not fully open.

3. With the high ambient temps here in southern AZ, I have placed an order for the nine XK engine/heater coolant hoses and will replace them soon, as well as the coolant pump, tensioner and serpentine belt. I'm not interested in stressing the engine in the event of a hose failure, especially since the layout of the engine in the engine compartment means it is almost impossible to see a leak until it becomes catastrophic. Its not easy to inspect the coolant pump unless the outlet tube is removed, as another example. The engine under cover can hold substantial fluid before any of it leaks out, since it has ridges cast into the cover.

 

If you check your fluids once a week you'll know if you have a leak.