XJR Supercharger coolant level

2002 XJR~100 coolant light comes on occasionally, butbthe coolant level is fine. So im wondering if this may have something to d0 with the supercharger coolant level,
Which leads into my next question, how do you check it and top ot off, Nd what xoplant do you use? Is itbthe lug ontop of the supercharger?

I probably should know this, but the XJR isnt my favorite Jaguar saloon. My daily driver is a series 3 XJ6. I just realized i havent driven it for 4 years. Wow!

It needs O2 sensors that im waiting for the parts to jump out of the drawer and onto car. It hasn’t happened yet so it looks like im gonna have to take matters into my ownhands and do it myself. While im at it i figured i should go through it and get it road worthy again.

Thank you

The super charger and engine share the same coolant system, so no need to check the S/C
The big lug is just for bleeding (but is below the tank level. DOH!) and they stopped using it on later cars.

Give the coolant float in the tank a bit of shove to ensure its free.
Maybe add a bit to the tank ?
I’m sure your coolant mix is correct.

I’m thinking about switching to Evans Waterless coolant. Any thoughts on this idea?

Thank you Andy for getting back to me on this.

yes the the mixture is correct.



The stock coolant type used is equivalent to Dex-Cool (orange coolant.) I always used the Prestone Dex-Cool widely available.

I see no benefit from Evans coolant in a pressurized water cooling system that justifies the trouble. Note that no OEM, not Bugatti, Ferrari or McLaren, uses Evans. If McLaren put gold foil insulation into their cars because of the benefits, they’d have no problem with Evans if it were superior. GM studied the coolant and found some benefits (as Evans themselves will point out) but GM never adopted it.

Evans is valuable, IMHO, in a non-pressurized cooling system like a Model T or many pre-WWII automobiles. That’s where it would provide benefits commensurate with the expense and trouble of converting to it.


dex-cool is what is in it now. I like the idea of never having to change coolant again; and the added benefit of no water no corrosion. Leaving coolant in an aluminum engine for long periods of time just makes me a bit uneasy.

As far as I know, corrosion is not a big problem with all-aluminum motors - the plague is if a high-silicate content coolant is used (which Dex-Cool isn’t as far as I know.) If left for a long period of time, the silicates precipitate out of the mixture and create deposits in the cooling passages. But unlike iron, the aluminum itself will not corrode and leave deposits just sitting there.

Unlike the XK engines, I don’t believe you have to change the coolant every 2 years to prevent silting. I left the coolant in my XJR for nearly a decade and didn’t have any silting problems. (of course it did get changed 3 years into ownership when the plastic thermostat housing hose fitting deteriorated and blew out my coolant, leading to a $3,000+ head rebuild bill, but that’s another story…)

After that, I don’t recall ever changing it, and that was more than a decade. If I did it was only once during that time span.


I’ll share my experience with my 1999 XJR sedan (28k original miles). Kept getting a coolant light but there was coolant in the remote fill tank. I replaced the level switch but the light would eventually come back on. Each check I did replace some coolant/water. It was a mystery until one day driving the light came on again. I kept driving, hoping to make it back home. All the sudden the Temp gauge went full scale and a clattering started in the engine. I shut everything down and was towed home!!!
Several factors were at play - all against the driver. First, the temp gauge is really an idiot gauge. It will stay center scale until the coolant reaches 220-degrees F or above and your motor is almost toast. Jaguar engineers “smoothed” the signal thru the computer to act in this matter. The gauge doesn’t give true coolant temperature readings! Next, there is a heater hose running in the engine “V”, under the super charger. That hose developed a leak at the pump fitting. As fluid would leak it would evaporate due to engine heat making it near impossible to locate! That was my main problem!
Bottom line - dropped 2 valves! Found a 31K mile motor/transmission and replaced the original motor.
If your car is over 10 years old I’d highly recommend replacing ALL coolant hoses. Not cheap but a lot less expensive than a motor replacement. Also, there is a kit you can install to mod the temp gauge to be a real temp indicator gauge.
Hope you solve your problem before it cost you $$$$$$…

Happy Trails,


thank you for the tip. I have gotten misfire codes which I figured these are O2 sensors issue since the car doen’t get driven much. It’s not my favorite Jag. I prefer the XJ’s of the Series 1-3 & my XJ-S variety. The cars got just a tick under 100k I’ve serviced the supercharger (rebuilt it). about 30k miles ago along with the transmission fluid that is supposedly not serviceable - lies i tell you!
I started getting miss fire errors and the temp registering coolant low levels. I figured the water pump was acting up. I have the replacement (for a bout a year now) and figured I’d replace it as a part of my Jag Mods YouTube channel. Just haven’t gotten that far yet. I will replace the hoses while I’m at it.

Thank you so much for sharing your story. That’s huge! I do have a spare S/C 4.0 and transmission from a 1999 XJR worse case. Though I’m suspect of it’s condition. I was told it had only 50k on it, but upon examination - I suspect this will be a rebuild candidate. I was planning on putting this in my XJSC track day Jag. but the older I get the longer down the road the seems to be.

Thank you so much for sharing your story. I haven’t had the guage pop up to overheat. I have had it drop in to limp home mode on a couple of occasions. but again, I’m thinking it has to do with the O2 sensors. I’ll start there I guess, pray my wife didn’t cook the engine. That would really suck.

Thank you for sharing