In checking the operating temp of 2001 XJR with outside temp in 90's I am seeing temps of 203 F to 207 F.
This seems high and I wonder if I have a defective/ non operative thermostat .
Frequent low coolant warning occurring. No visible leaks or collapsed hoses .
Squeezing major hoses resulted in burp at fill reservoir
Initial AF level was just above the base of recovery tank . Sensor was free to move up tube { a little dirt on it} . cleaned it . Topped of with AF.
Ran for 10 mins with cap off and turned heater on /off 3 times . Noticed some minor burping and AF level changes. .
My real concern is the high temp readings . Normal for Texas Heat ?
Intake temps were 136F to 147F .
Any suggestions

 

Hi Graham,
Sounds like you have some air in the system. To achieve the correct amount of cooling you will need to get all the air out, assuming you definitely have no leaks.

 

Are these temperatures when you are stationary, in traffic, or highway?
If stopped, are both fans working.
On an 80 degree day, stationary, my fans cycle from 194 to 200, so your temps are still reasonable.

 

203º-207º doesn't seem all that high to me, especially with ambient heat 90º+. That's about where my XJR/6 runs under similar conditions, FWIW.

You probably have a (approx) 195ºF thermostat so we know the engine will run *at least* that hot no matter what.

In a perfect world all cooling systems would have enough capacity to hold temps rock solid at the thermo rating temp but, in reality, not all of them do. In fact, many don't.

Cheers
DD

 

My 99 XJR seems to run at 185 degrees, regardless of outside temperature. Of course, my driving is all rural, so I haven't checked it in traffic yet. From what I've seen on this forum, 185 degrees should be the norm.

 

How do you guys know what the exact temp is?

 

I presume they're using a scan tool, as I do.

Cheers
DD

 

That would be correct. I use the Actron CP9575. It seems to be a great scanner, for the car owner on a budget, like myself!

 

The stock thermostat is 195


This one is 180, fully open at 185, I've found this reduces the time the fans are on a bit while sitting in traffic.

Jaguar Low-Temp Thermostat - Jaguar Performance Parts

 

Somehow or another, folks have decided that a cooler running engine is somehow "better"! The engine management system depends on the engine maintaining a minimum temperature in order to have peak efficiency. That is why there is a thermostat and why it is set to a certain temperature. If you are overboosting your supercharger, running the car at the track, or doing something causing some other engine management change, there MIGHT be a reason to run a cooler thermostat. But if you drive more normally, the cooler thermostat will not reduce the maximum temperature in a overheating situation, it will reduce mpg, and it might cause excess condensation and sludging in the crankcase and breathers.

And, just look at your bottle of coolant. With the pressurized system and 50% coolant, your coolant will not boil up to 265 degrees f.

This discussion is exactly why manufacturers do not put numbers on the guage and do not have a linear movement. People get all freaky when the temperature goes a little over the thermostat opening setpoint.

 

Yes, all of the above is, of course, absolutely correct, there is an optimum range, and there is too hot and too cool. I just like knowing the thermostat is fully open at 185. If the 195 starts sticking a little, there is less room before trouble can set in. The car will still run around 200 in traffic, even with the lower thermostat. I have found that the fans kick on less, which, for me, is enough of a reason to switch to the 10 degrees lower unit.

On my new supercharger set up, I'm running 15+ lbs of boost on a heaton, so to delay overwhelming the cooling system a few seconds (maybe the last 3 of the 12 seconds of a 1/4 mile) it is worth the extra few degrees lower temp/heat inertia starting point. I can turn on my fans at idle, spray a mist in front of my inter cooler radiator, and start with everything a little colder. If I wanted my car to better resemble a prius, or am going for smog tests, I could throw the 195 back in. That takes only a few minutes.

If I were most interested in passing smog I would run the stock 195.

 

Thanks , I burped the bad black cat , cycled the heater 4 times and the warning has gone.

Txs Jimbov8

 

Hi Graham,
Hopefully that's you and your cat back up and running. Happy to be of some assistance.