engine coolant low warning

This is an old thread but somebody may be interested.
After having and solving some cooling problems 3+ years ago I have found it increasingly difficult to keep the 'Engine Coolant Low' message extinguished.
The only way to avoid the message was to have the header tank almost filled with a 50/50 mixture of antifreeze/water (not necessarily a bad thing).
I replaced the level sensor but this had no effect. The problem appears to have been the float within the header tank (it wasn't always living up to its name).
To solve my latest coolant leaking problem I replaced both the header tank and its cap and the errant 'Engine Coolant Low' message has dissapeared.

Related question: how full should the header tank be?
Up to the top/bottom seam or up to the neck?

Cheers,
Aidan

Thanks Doug,
I think you are on the right track,I will try to do as you suggest.At least that way I will know if it is the sensor.

Ok, I also have been chasing this problem- searching the forums, etc. I tried the remote tank filling, which didn't seem like the right direction to head, as it doesn't remedy the cause, just addresses a symptom. And it didn't work anyways. I finally found enough free time to chase down my problem, and sure enough, it was the sensor on the little header tank. Here's a relatively easy troubleshooting technique:
Loosen the header tank for easier access- remove the screw on the (vehicle) left, remove any wire clips (there's one on the back hose), and free the tank from the engagement pins underneath. This will give you access to the sensor wire plug underneath the tank.
Remove the small wire clip from the plug- carefully pull it out with a pair of needle nosed pliers, and try not to loose it. Now you can disengage the wire harness from the sensor.
I fabricated a short jumper wire from some small wire I had, I think it was 18 gauge stranded. It has to be small enough to jumper the plug receptacle on the harness. I shorted the wire harness contacts together and wha-lah! No warning message- it's the sensor.
I haven't bothered to change the tank/sensor yet. Truthfully, I'm driving it with the jumper wire installed, since I can periodically check the coolant level myself. (I zip-tied the plug up for access.)
I'm not sure if only the sensor can be changed, or the entire tank has to be changed, but that's for another day.

Thanks for all the information and advice.I will get to it after the holidays.Brian Myerscough.

The manual filling thing is to add coolant to the atmospheric tank so there is some to draw back in during cool-down. You do that if the header tank continues to seem to loose coolant. If yours is always full and still shows a low warning, then my first response applies.

Cutting the wires? That's just dumb!

Cheers,

On a previous Forum,the advice was to make sure the expansion tank was full by manually filling from the elbow connection on the top header tank.Some times this worked and at other times the problem came back.There was also talk of a Jaguar dealer recommending cutting the wires to the sensor which I thought was a bit over the top.

Edited on 2011-12-16 12:47:16

Brian,

Both those sensors operate the same way. There is a magnetic proximity switch that pushes into the bottom of the small header tanks, points straight up. Inside the tanks is a magnet on a float, when the float sinks far enough it closes the proximity switch by magnetism. The float either gets stuck, or it fails to float. If stuck, sometimes it can be freed, but usually the tank has to be replaced to assure no further problems. That is if you are sure the thing is full, and still shows the warning.

Oh, the sensor pushes up into the tank and snaps in; it is possible the little retaining bosses have failed and allowed the sensor to fall downward. That could trigger the warning as well.

Hope that helps!

Brian not sure what you read before but that is normally a symptom of a failed sensor or wiring to the sensor.