My "Coolant Level Low" warning light came on. I checked the reservoir and it's just a hair low. Is it okay to fill with some distilled water or do I have to use the Jaguar fluid?

Thanks

 

Topping up with distilled water is perfectly OK.

 

But ... work out if it's leaking

If your fluid drains out the engine will overheat and be destroyed in minutes (or less). Don't risk it!

 

Thanks!!

 

Kjamo, keep an eye on things. I just had this same issue and what it turned out to be is the expansion tank failed. I guess this is a big problem with the XFs, XKs, and F-Types with the 5.0L engines. In short, the float is set to barely float in coolant and over time, it gets heavy and will sink, causing the alarm. This normally requires you to replace the expansion tank. It isn't a hard job (took me about a half hour), but it can lead to some cautious driving to ensure the car doesn't overheat. If you need more info, let me know.

 

I've had this experience too. and had the expansion tank replaced.

 

Has the water pump been replaced yet?
If not I would suspect it's leaking.
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Thermo, XJsss and Clubairth1 - Thanks all for the feedback. The water pump has not been replaced. The bad float in the expansion tank makes sense as when I look at the the tank, the level honestly seems to be right at the line. It seems like not more than a couple of ounces of water at most would be needed. I'm going to add a little water but will keep an eye out and post if anything changes.

Again the help is much appreciated!

 

KJamo, what most people see with the bad expansion tank is you can start up the car cold and all will be good. Then after about 5-10 minutes of driving (ie, once the engine gets up to temp and been there for a few minutes, you will see the low coolant message. In short, what is happening is the warm coolant is finally making it to the expansion tank. Since the warm coolant is less dense than the cold coolant, the tank float doesn't have the buoyancy that it had with the tank cold. Therefore, the float sinks.

I haven't looked at the float all that closely, but I do know that it is got something special in it as it is not just a simple hollow ball with a magnet in it. It needs the higher density fluid of 50/50 mix coolant/water. If you were to fill the expansion tank with just straight water, you will still have the low coolant light. how do I know this? When I flushed my coolant system, I noticed the low coolant light was still on even though I knew the tank of borderline overflowing.

I wasn't sure if you might not find this information interesting.

 

I have a 2011 XJ supersport today the coolant level low warning came on. This was following an emergency stop. I cycled the ignition several times after but the problem has remained.
Having read multiple forum posts on the subject suggesting replacing the tank and sensor I figured I would try the simple stuff first.
Given that the coolant level has not changed in 3 years of owning the car I figured it had to be the sensor. The car does always put out steam from the exhaust when the weather is cool and when examining the steam with my finger and tasting (sounds gross) it is just water vapour and not the dreaded head gasket leak. Water is a bi product of petrol burn so I expect it in a 5Litre engine.
As I did a rapid stop I figured the coolant had shifted to the front of the tank and set off the sensor. Maybe as I stopped on a rough country road maybe it was jolted and got stuck.
I waited for the coolant to be cool enough to remove the tank cap and inspected it. I considered poking a pipe in the an blowing some air in but lack of a pipe I resorted to giving it a bit of a Clarkson. I started shaking the tank and gently banging it and also gave the connector a wiggle and checked it was connected properly. After a minute or two of tapping the tank and shaking I put the lid on. I turned on the ignition and the warning light had gone.
I would suggest giving it a good tap and inspection and maybe having a gentle probe if this fails before it becomes and expensive fix.
I did note the coolant does smell a little hot or burnt but it's colour and condition coupled with the way my car runs would suggest this is probably normal after 25k miles. It tasted as it should and will get a flush as dictated in the service manual.
I know my problem was just caused through an extreme driving situation but it should still be considered if the problem arises. I would also take note that when freeing the stuck float the coolant was close to operating temp so may of made it easier to free off.

 

jonny, in my case, I could run the car, get the warming, turn off the car and let it cool with the problem clearing itself on the next start. But, after 5-10 minutes of running, the light would come back in. So, yes, your case may be an unlucky situation where things were just so. But, for those that find the level normal and then getting the light multiple times, I would be looking at replacing the expansion tank.