The 'idiot gauges' started before the X308-my old 1995 Daimler Double Six had the fantastically useless 'oil pressure gauge', that was basically a gauge connected to the same on/off oil pressure switch that drove the oil pressure warning light!

So the gauge would either be off or in the middle!

At least you do get some 'linear' movement in the X308 temperature gauge before it hits the 'dead spot' in the middle, where the needle won't budge over 30 degrees or so of temperature...

 

Yes, the XK8/R is the same, with the oil pressure gauge essentially connected to the idiot light! I offer an oil pressure option for RealGauge for the XK8/R.

Yes there is linear movement in the factory gauge from 125 F to 185 F (50 C -85 C). The dead band is roughly 185 F to 235 F (or 85 - 112 C). Unfortunately the dead band is exactly where you need it most !

 

My daughters Beetle has a blue light if it's cold and a red one if it's hot. I rent a lot of cars for business, and many have no temp indication at all. Reminds me of the Turbo Capri I drove for a while. It had an "engine" light which came on for loss of oil pressure OR overheating. Not very helpful. It might as well have had a dollar sign on it.

 

I have just completed my XJR rebuild. I tested the thermostat, but can't remember what temp it was. At any rate it runs around 203 F, which makes me uncomfortable, if only because my XJ8 with a 170 thermo, runs at 185.
I guess I am asking, is 203 F ok to run at? Since this car already blew a head gasket, I am cautious.

 

203 F is "normal"

You can buy a 180 thermostat if you want from Eurotoys. It is fully open at 185F, your car still will get to 203 when sitting in traffic.

Just for fun, I added a 12" pusher fan in front of the inter cooler radiator that has a manual on/off switch in the cabin.

 

Thanks, WD. The reason I posted this here is that I bought another Realgauge for the XJR.
Eurotoys website is a bit unclear on the details, so I have emailed them asking for more info.

 

203 is fine. Just idle the car for a while and monitor the temperature and make sure the fan comes on by 215 F and drops the temp back down to around 200.

 

Mike from Eurotoys confirmed theirs is a 170, so I am ordering one. As for the fans, I tested that they came on, but I will double check using the test unit and OBD to see what temp it takes. I recall it was a bit high before they came on.

 

I bought two from him 9 months apart and tested them in water with 2 thermometers and they both start opening at 180 and are fully open at 185. The two stock ones opened at 195-198 that I tested. I tested these myself because I do not trust stamps or any other "trust me" slogans. It is unproven until it is proven. Imagine installing a faulty one without having tested it first, eeeeek!

My fans come one at 204 F and off at 193-194 F.

Maybe the 100% of my sample size of only two was misleading in that is is "possible" that he "mistakenly" sent 2 complete anomalies to me 9 months apart that opened at exactly the same temp, and his "usual" thermostats he sends open at 170, but my experience, tested via reliable thermometers says they are 180 thermostats, not 170, which is a better temp range anyways. 170 is too cold.

He may just be saying 170 vs 180 because that may be what he thinks you want to hear.

I'm sure he would be unhappy with me posting this, but too bad. These boards are for us to share the correct information, not walk on eggshells to avoid exposing sellers, um...."marketing bendings of the truth"... I know I ruffle a lot of feathers telling the stone cold truth, or at least my personal experience. But, again, this is one of those things that makes this board so useful.

The 180 thermostat he sells is a very good product, and I do appreciate that he makes these available, but an improvement would be for him to give the correct information about the true temp of what he is selling, especially since the 180, in my opinion is a better operating opening temp than 170. Sitting in traffic with no air flow, your car will still get to 200++.

The stock 195 is just fine too, but I prefer to not have my fans coming on so much if sitting in traffic. To each his own, just my 4 cents.

My testing procedure was to slowly heat a pot of water with 2 reliable meat thermometers in it. The thermostats were held off the bottom of the pot with a strainer so it was only the water temp and not the contact temp of the pot heating them. (this is how I made eggs 63C before I bought a sous vide water oven)

I request that when yours arrives, please confirm or refute my above claims by testing the thermostat the same way and making a new post about your results.
If I am incorrect, I will immediately correct this, or any other of my posts if it is proven that I am in any way inaccurate.

And the real gauge is the real deal. It is a must do mod.

 

My car, with the Eurotoys "170" thermostat cruises down the highway at 185 F, and the factory thermostat cruises at just under 200 so your findings jive with my experience.

 

You guys are funny with you Tstat stories.
What a lot of peoples don't seems to understand is that a thermostat only control the MINIMUM engine temperature, not the maximum as it is often time implied in thermostat discussion
What control the MAXIMUM engine temperature is the system capacity in BTU's ( British Thermal Unit)

 

Absolutely true.
When cruising down the highway on a vehicle like a Jag with a highly efficient cooling system, there is sufficient airflow to overcool, so you are effectively seeing the minimum temperature of the thermostat. This can be demonstrated by remving the thermostat and never reaching operating temperature while cruising. I stand by my comparison under these circumstances. If you are idling or driving aggressively, it is a different story.

 

Tienne reason, mi amigo, which is why I said in the middle of my post: "Sitting in traffic with no air flow, your car will still get to 200++"

Since I wanted to be able to control idle and long on boost temp scenarios, Which would be much much harder to do with a 195 thermostat, I've added a manually controllable 12" pusher fan in front of my inter cooler radiator for when the car is not moving, or is moving very slow in traffic, or right before a race.

I also have a fine mist water spray, which sprays my inter cooler radiator, and thus later the engine radiator too. It is also manually controllable and/or auto on boost for long boost periods, like on a road race course. This way I can cool everything down to near thermostat opening temp even if I am at a stop with no flow over the radiator from car movement, or have added cooling while on boost for long periods. This has put the temp control back over to me, the driver. The 180 temp thermostat makes it easier. While not running the car hard in regular driving, it is my opinion that a 170 would be too cool, which is why I think the 180 is better, because, as you say, the thermostat it sets the minimum, not the max. It is my opinion 180 minimum is better than a 170 minimum for our applications.

If it is hot out and I am in traffic or idling I can elect to turn on the 12" pusher fan, or not.
If I am about to race I can turn on the fan and cool the inter cooler circuit with the fan and fine mist water spray and get all temps down before the run.
If I am on boost for long periods I can run the inter cooler spray which reduces IATs in the 20 degree F + range, as well as provides extra cooling capacity for the engine coolant radiator. I can also adjust how much water sprays from 200ml/min to 2000ml/min to suit my needs.

or I can turn each or all on or off as I please

 

Either you have sufficient cooling airflow from a fan or ram air, in which case the thermostat will set the temperature, or you don't, at which point it will overheat.
There are some variables, such as airconditioning(which raised my temp to 210 yesterday)
and ambient temperature, but IMHO the thermostat is the primary driving control over water temperature.

 

Speaking of temperatures, what is the temp sensor on the back of the RH intercooler called, and what does it do? BTW I will post detail of the thermostat I bought later today, after I've had a chance to test everything out.

 

That is the IAT #2 sensor

 

No matter who you buy a conventional thermostat from there will be a number stamped on the thermostat by the manufacturer.

It is the rated opening temperature in degrees celsius. That is where it cracks open. Fully open is 12*C above the rated temperature. Those are the standard design parameters in the industry. Of course, as the whole thing is controlled by a "calibrated" wax pellet and springs, there is some variance.

For your convenience:

Temperature Conversions, celsius to fahrenheit - online temperature converter - on-line temperature conversion

Because of hysteresis designed into the fan controller, while it turns on at about 205*F, it turns off around ten degrees lower than that. Unfortunately, it is at a temperature that the system has a hard time reaching with the stock rated thermostat.

With a lower rated thermostat, expect that once fully open and watching with a gauge that works, when the car is at a standstill a long time, the cooling system will look like it is in thermal runaway until the fan set point is reached.

On other makes, a installing a lower temperature thermostat is coupled with reprogramming the fan controller or using a different fan controller. This is done to match the fan behaviour with the new lower running temperature.

 

I can't offer an opinion on the Eurotoys unit, as I didn't buy one. I found an alternate locally, seen here- https://www.jaguarforums.com/forum/x...59/#post792421

Mike was very good, responding to emails well outside business hours. The price was ok, but when I got to the shipping part, the lowest charge was $22. This seemed a bit steep for such a small item . I emailed Mike and he offered to make some adjsutments, but by that point I had found my own unit.

 

A minor update- My XJ8 is rock solid on the temperature, whereas the XJR will vary from 180ish on the highway on a cold day to 200 in heavy traffic. I'm happy with both, I just find it curious that the one varies so much while the other is always steady.
But they are very different cars because of the intercoolers.

 

More power, more heat? Differences in the cooling efficiency of the specific set ups? Allan