Here’s an odd one, my coolant warning light on my 2004 XK8 came on last week, so I checked the reservoir and added a little coolant. It wouldn't go off so I searched the site checked the sensors, then on a whim I squeezed one of the radiator hoses which burped some air out of the system and I added some more coolant. About a cup total.
The light returned today, the reservoir is full and squeezing the line has no effect.
Is the sensor in the in the reservoir the only sensor that monitors coolant level and is there anything else I should try?

 

I find that my low coolant light goes on if the level is more than about a 1/4" below the neck of the fill cap. And if I park on an incline with the front facing down, it routinely goes on until the car is level. Just keep it filled close to the top and watch your temperature gauge regularly, and I wouldn't worry about it.

 

Did you check this recent thread for problems with the Coolant Level Sensor in the bottom of the Expansion Tank. It can stick and give false warnings:

https://www.jaguarforums.com/forum/x...-sensor-71865/

This is the sensor that trips the warning message and does so because of low coolant volume.

The coolant temperature gauge (if you have the three centre gauges) is little more than decorative and won't move much until the engine is dangerously overheated.

Air in the system other than after the radiator has been flushed and refilled is unusual. If you get air in the system at other times, there may be a leak.

The Expansion Tank is connected to an Overflow Bottle in the front wheelarch:

JAGUAR XK8 - Expansion Tank & Recovery Bottle.pdf

As the engine gets up to temperature and the coolant expands, excess from the Expansion Tank is piped to the Overflow Bottle. When the engine is switched off and cools down again, coolant is drawn back from the Overflow Bottle to the Expansion Tank to maintain the correct level.

Keep an eye on the coolant level and investigate further if it drops or there is air in the system again.

Graham

 

The coolant level sensor contacts are operated by a floating magnetic 'donut' riding on a hollow post inside the reservoir. It can become stuck due to old coolant junk and create erratic readings. Use a long handled spoon or something similar to move the magnet up and down. That is more often the problem than a bad sensor.

 

What type of sensor you have? Float type or Magnet type.

 

I had that warning, but I was actually low on coolant

 

So here's the follow up. I took the car to the dealers to make sure it was the sensor and not some odd ball electronics issue. as I expected, They said I need a new coolant tank, since its on order and I have an extended warranty it's cheaper for them to do it.

 

I've just been down this path and documented my experiences a few days ago. My problem was the wee magnetic rod that sits in the doughnut float falling out (why does it not sit in a blind hole as opposed to a through and through hole?). First time I found it in the reservoir and it was replaced with some fiddling. Fell out 24 hours later and has disappeared, presumably magentically stuck to the side wall of something somewhere.

Car now at the dealers and, although all I need is the small magnetic rod (or conceivably a new and 'complete' float), I bet I'm up for a new tank. Thank goodness for extended warrantees; don't ask how they can help in the wallet when it comes to supercharger problems.

 

My 2002 xk8 has a low coolant message I intend to replace the sensor, can I simply remove and replace the sensors from the tank. Looking at these earlier dated comments I am not sure if the 2002 tank is not one piece ?

 

That was my experience, too. Not all warnings are system flaws .

 

The “sensor“ is actually a touchless Reed Concact with a magnetic floater inside and a microswitch outside the tank. so if you want to solve the problem you probably have to change the assembly.

there are currently a series of faulty expansion tanks in the after market. the sensor doesnt work and causes wrong warning messages. guess why i know this.

fritz

 

I went to purchase a new sensor. Parked the car on an uphill slope. Came to leave and the current sensor is now functioning correctly after two weeks of showing low coolant. A little rise helped??

 

But this technical bulletin seems to answer all the questions that I read over here on many forums.

 

I would bite the bullet and go to Partgeeks.com and buy a new tank for $50.00 (U.S.) I looked at my low coolant warning light for a long time, keeping an eye on the coolant. I just changed my tank yesterday and the light is off. Turns out my sensor float had sunk, then somehow had swollen up around the sensor tube. Also, the replaced tank was original to the car (said Jaguar on the bottom) and was deteriorating because of age.

The only difference between the two tanks was that the new on rattled because the float wasn't stuck...

 

After checking to see that coolant level is up to neck of tank but before buying new tank, stick your longest finger into tank toward back and see if you can feel the sensor. If it’s the magnetic “donut” on a post type, you may be able to flip/ move the donut up and down and spin it around a few times. Don’t know for sure what was restraining the donut from moving freely but it worked for me. Lights been off for 5 months now.

 

I had same issue,replaced the tank sensor with new one from rockauto,it did not cost much and it fixed the problem.

 

I figured I would add to this thread since my experience is related.

I did replace the coolant tank with a new one. DIY details here. That was about two years ago.

Recently I started having intermittent low coolant warnings.

Tank is fine and no fluid loss so I looked into the sensor that plugs into the tank in the bottom.

Noticed a couple things:

1. The new tank sensor's post that extends up into the "hole" in the tank is 1/8" shorter than my original (yes I kept it - I am like that).
2. The blades in the new tank sensor's connector are thinner than on the original, causing a weaker/poor connection.

My findings were enough to warrant a change in sensor.

So I simply plugged the original sensor back into the new tank.

Problem is solved. Not sure if the new sensor was just failing, had inferior connectors, or was of inferior design (it is way different materials). But it was definitely the sensor causing trouble.

So if you do end up replacing the tank, pay attention to the sensor connection, maybe keep the original sensor in case you need it like I did.

 

I have a 2005 XK8 and have just replaced the sensor due to the low coolant warning light on the dash. The light is still on does anyone have any suggestions as to next steps?

 

We will assume that you do have a full coolant tank...so...

If the float is stuck inside the tank then replacing the sensor won't help and you need to buy a new tank and replace your old tank.

Could also be that the float is just no longer floating and you need to buy a new tank and replace your old tank.

Could also be the connection at your sensor is not good.

Since these tanks and floats are known to cause trouble I would just buy a new tank and replace your old tank as a starting point.

 

Thanks, will try a new tank and see if that solves the problem.