Hi all,

After about a month of work on the cat (new rear diff, exhaust, intake, pulley, struts, brakes, etc), she's just about ready to be put back on the road.

I was wondering if these engines were prone to overheating as I had heard complaints about the XJ8's in the past.

Are there any measures I should be aware to take to ensure the car doesn't overheat/give any problems being used as a DD aside from general maintenance?

I'd appreciate if anyone could share their experiences.

Thanks a lot

 

First thing to do is figure out if it IS overheating. The built-in temperature gauge is fairly useless, so hook up a scan tool like the Ultragauge which allows you to see the true engine temperature in real time.

I ran my vehicle for a few days like that, the temperature was fine, so I unhooked the Ultragauge and called it good.

Another good thing to do : pressure test the cooling system to find and eliminate any slight leaks.

 

Thanks Mark,

Wow I had no idea such product existed, I know there are similar ones on the market but I just did a quick research but for the price it seems like a great deal!

Thanks a bunch!

P.s. have you experienced any issues other than overheating while driving as a DD?

Thanks again

 

I am not sure from your question if you have the impression that XJRs have cooling problems or not. I do not think they do under anything like "normal" circumstances nor do they have any other peculiarities that I can think of, at least as they came from the factory. That why buying an XJR instead of hopping up another car is a good way to have a fairly good hot rod. And you are driving a Jag-u-wah!

 

Yes, I agree that the cooling system, when working properly, is totally up to the job. This especially seems to be the case if you have ever owner a V12 XJS, which does provide something of a contrast and reminder of how far Jaguar's quality has improved in quite a short time.

However, at the age of our cars, problems can creep in, especially if previous owners have not been dilligent about coolant changes.

 

I've driven my 1999 XJR across the country and back, doing 600-700 miles a day 75mph+ without any heat issue in August 2015. Check gauge and rad fluid low/leaks, wate rpump issue or is it straight water? .. ..

 

Yes get a OBD Bluetooth scanner & download the Torque PRO app, you can then monitor loads of vital data(temp.,vacuum,etc.) in real time for $20 total investment on your chosen device.

 

The engine is unforgiving -- they are easily damaged when overheated.

It's common for Jaguars when they move past the original owners to suffer from neglect -- With proper basic maintenance the cars are very reliable.

The early cars had water pump issues -- Many were allowed to fail way past the point that everyone understood they should be replaced.

 

The modern "idiot" temperature gauge can cause problems, as they are programmed to read N over a wide temperature range. This can hide chronic overheating, which can be just as damaging over a longer term as a sudden catastrophic failure.

 

If the cooling system is well maintained theres no reason why overheating should occur - the point is IF the engine overheats to the point that your "guage" jumps to the red, its more than likely too late to prevent some major damage.
Apparently Jaguar didn't fit a proper guage as they didn't want customers to fret when the needle fluctuates in different driving conditions as a proper guage would. Go figure....

So latest water pump/tstat housing, coolant flush/changes and tstat changed fairly regularly together with regular inspection of the hoses should see you through.

 

For those unaware, my RealGauge is a permanent solution to the inadequate temperature readings that uses the factory gauge.

It also includes preset audio alarms for high temperature and low oil pressure.

See: XK8 / XKR / XJ RealGauge - TheJagWrangler

 

Have to agree with the above. As long as the system is maintained, should be nothing to worry about. I daily mine about 75 miles a day to and home from work, and last summer took it to Louisiana and back with upper 90s down there (and uncharged AC... give you a guess as to when I realized that...). 135k miles, still rock solid, and I'm about to do an even bigger road trip and have no second thoughts about getting in and going.

 

And that is the real basis of the supposed problem.

When everything is working right, the cooling system is sufficient.

But, if something goes wrong, you have zero warning of impending
doom. Overheating an aluminum engine is not quite the same thing
as overheating say a cast iron Chevy SB.

Because I run a lower temp thermostat, the needle pegs at one mark
below the middle mark at highway speeds anywhere from 50mph to
90mph. It is still in the "active" part of the gauge because it is
below the middle mark where it effectively goes dead. If it moves
above that mark, time to stop.

I have a digital gauge with adjustable alarm relay for a BRIGHT flashing
LED awaiting integration into the dash area, but the above will do for
now. Come to think of it, I can leave the guts in the engine bay and
just run the LED in the dash.

 

Oh wow....thank you all

I had NO idea about any of this, and I thought my GT3 was a PITA with overheating problems. I guess I have to opt for the OBDII real time reader. Thanks for this.

I take care of my cars, but they're by no means garage queens and I'm not one to go over with a magnifying glass to every spec I see. Woof. Coolant change this week for sure!

What coolant do you guys use, and what intervals do you change?

Thanks! Trying to get as much life out of this Jaaaaag as possible. Best DD I've had to date, plenty more fun/feel for the road than my 2015 SQ5

 

In all fairness to Jaguar -- the gauge issue its a bit overblown. Yes, it's a median balanced gauge -- it's factoring the normal range. The sad truth with modern engines that all run at elevated temps -- if something goes wrong .. they overheat.

 

I run the Panlong for Android linked below w/ Torque Pro APP.

 

You commented at the beginning that you heard the XJ8 was known to have a overheating problem, and that is sort of true. When the thermostat fails on the NA V8 it sometimes sticks in the closed position, thus causing overheating.

I don't recall reading of this happening with a SC engine.

 

Hmmh. They are the same thermostat. And I do not think XJ8s would be characterized as having more thermostat failures that the average car, although I agree that a failure will cause an overheat, with potentially catastrophic results.

 

Hi Mark,

Just to confirm, is this the ultra gauge unit you are referring to?
It doesn't have Jaguar listed as a compatible vehicle but it makes it sound like it'll work with anything that has OBDII.

Please let me know if this it. Also, can you use it to read CEL's?

UltraGauge EM Plus [UltraGauge_EM_Plus] - $69.95 : UltraGauge, OBD II Scan Tool & Information Center

Thanks again

 

Sparkenzap, didn't realize it was the same thermostat, must be just the greater number of NA engines gave the impression of more failures.

PC210- I have been using the Ultragauge on both Jags for a few years. It's necessary to force the protocol to 9141, but that's easy. You can set a temperature alarm, monitor fuel trims, and read and erase engine codes. They even have a wireless version now.