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The low coolant light has come on ever since I got my jag about 2 weeks ago and a quick check confirmed there is plenty of coolant in the reservoir so I did some research on the forums and found out the sensor can get gunked up and you need to locate it on the tube it rides up and down on and move it up and down a few times to free it up so it floats properly. When I went fishing in the reservoir with both a plastic spoon and then my finger I can find no tube or magnetic sensor. I think the previous owner may have removed the darn thing! Ugh!
A very common cause of the low coolant warning is air trapped in the cooling system. See the procedure for properly filling and bleeding the XJR cooling system at the charge air cooler fill point, which you can read in the Workshop Manual excerpt at this link, courtesy of our member Jim Lombardi:
Don,
If I am correct and the sensor has been removed how will checking the electrical connector help?....lol
One of our X308 owners will have to confirm, but I believe the coolant level sensor, Part 3 in the diagram, is external to the reservoir but its long probe (the vertical "rod" in the diagram) fits up into a recess on the underside of the reservoir. The recess is the inner diameter of a deep socket or "tube" molded into the reservoir.
Inside the reservoir is a magnet on a float that rides up and down the outer diameter of the "tube," rising and falling with the coolant level. The sensor "senses" the level of the float/magnet.
When air pockets get trapped in the coolant, the float/magnet can fall and give false low coolant readings.
It would be possible to remove the coolant level sensor, but I don't think it should be possible to remove the float/magnet from inside the reservoir.
Again, I'm hoping one of our X308 experts will confirm, but you should be able to locate the coolant level sensor on the underside of your coolant reservoir.
I also have a 'Low coolant light " on. I had my engine replaced a month ago and the light was intermittent after that, now it is on all of the time. I have replaced the sensor and it's still on. Another nore: my heater does not work and it did'nt before the replacement engine either. Could my heater core be clogged? Any ideas?
The heater core could be plugged or the heater pump not running. It may even be air in the line.
The low coolant light may be because the float in the tank is stuck or just not floating. Do a search for pressure tank float for ideas on how to proceed.
No. I remove the 19mm plug on top of the intercooler, but many don't. I find the most effective way is to squeeze the upper radiator hose repeatedly to pump coolant through the bleed valve in the thermostat.
The brushes on the heater pump do wear out. There are posts in the archives on this. I replaced mine with model electric car motor brushes. They are available on the internet. I don't remember the size, but I think it is in the archives. It's a little fiddly, but cheap to do, if you want to take the time.
On the original subject of the coolant level sensor - the float is in the reservoir and can get stuck, that's when you get in there and make sure it goes up and down on the little shaft or tube. Underneath the reservoir the sensor plugs into the reservoir. It's a little delicate shaft that stick up in the preformed tube and has the connector attached to it. It snaps in place but is external to the reservoir tank.
Coolant sensor
