Hi guys!

Where is the coolant level sensor located? After the new (used) engine went in, I get an engine coolant low warning even though the level seems fine. There doesn't seem to be one attached to the reservoir.

Thanks

 

The sensor is inside the expansion tank. The connector being underneath by the hose. Perhaps it was not reconnected.

 

The Level Sensor is Item 4 clipped into the base of the Expansion Tank.



Graham

 

Haha.... You just solved an even longer mystery. The PO left some odd ball looking thing in the console that looked just like item #4
Thanks!

 

Speaking on the coolant expansion tank, what is the proper level for the coolant in the expansion tank. I thought from reading the manual that it was just above the bottom of the tank but my coolant light is still on at that level.


Mark

 

The design of the XJ/XK coolant system is a pressurized reservoir and then an overflow bottle. Fill the reservoir cold. As it heats it will drive the surplus coolant into the overflow container and then suck what it needs back into the reservoir as it cools. Given a little fluid in the overflow it will regulate itself to where it thinks it should be.

 

Mark, by bottom of tank, I assume you mean bottom of the filler opening. You could have an issue with your sensor, the float, the cap or the tank itself. The floats in these tanks can get saturated over the years and lose their buoyancy. They also like to get stuck. Try opening the tank and with a screwdriver or other suitable probe pick up the float manually. If the light goes off, there's your problem.

The bad news is that it often takes a new expansion tank. The good news is that they come with a new cap and sensor, plus they are easy to change out yourself. Plenty of threads here to show you how.

 

The Vehicle Care Handbook states the correct level is to the bottom of the filler neck (see section boxed in red):



(click on the image to enlarge it)

Jaguars don't 'use' coolant. The level should never drop unless there is a fault in the cooling system.

Graham

 

I had work on performed on my coolant system this summer, which in Texas is HOT. This fall, when the weather turned cold, I keep getting an intermittent "Low Coolant Level" message. When I checked the tank level it was down a little from the neck where the cap is located. However, when I read the manual, I was not certain that I understood the directions correctly and didn't know there was another expansion tank. I understand now and believe that this is the result of the change in average air temperature from about 100F to 50F. Thanks for the info.


Mark

 

This is the Atmospheric Recovery Bottle (arrowed in red) in the RH front wing.



Excess coolant from the Expansion Tank goes through the transfer pipe (arrowed in green) and is drawn back as the engine cools down again to maintain the correct level.

If the Atmospheric Recovery Bottle fills completely, coolant is dumped onto the ground beneath the vehicle through the overflow pipe (arrowed in yellow).

With the exceptionally hot weather you have had in Texas, this is quite possibly what has happened to cause the slight drop in Expansion Tank level.

As long as you have no leaks, there's nothing to worry about.

Graham

 

Thanks Graham, this was my conclusion as well after you guys explained the design of the system.


Mark

 

Well, after reading this I rooted around the little reservoir and found a couple of surprises. Seems there was this connector hanging around loose with a jumper wire that had come free. Also found that the outside part of the sensor was broken off. Well that explains the low coolant warning and probably means that the weird looking thing I threw away a couple of months ago was a new sensor that the PO "meant" to install. Just shoot me now.

And so goes life in the big city.

 

A new Expansion Tank comes complete with the sensor fitted.

You may want to consider replacing the tank if the PO has already been playing unsuccessfully with it.

Graham

 

Thanks Graham. Yeh, I'm considering that because with the sensor broken off I'm not sure how I'd be able to remove it. In the meantime I'm no worse off then the old days when we just eyeballed our fluid levels periodically.

Ciao! - Jim

 

Hey guys,

I bought a used sensor cheap just in case I want to try a swap. For the life of me I can't figure out how it would go in. There's just a circular ridge around the base. No tangs; no threads; no seal. How do you swap one of these with confidence?

 

Pull out the old one and push in the new one. It may be easier if you remove the tank.

 

Interesting.

I can't imagine how it would stay put under the pressure of the cooling system.

Well, I've got to remove the tank to get to the exhaust down-pipe nuts sometime in the future. I'll check it out then.

Thanks!

 

The sensor is not under pressure. It slides into a tube built into the tank body. There is a magnetic float inside the tank which activates the reed switch in the sensor through the plastic housing.

 

Brilliant!

Thanks White.

 

Thank you for this! My mechanic forgot to connect #4 and this diagram helped me clear the "Engine Coolant Low" warning.