XJ8 4.0L Low Coolant Warning light on

(XJScharlie) #1

Hello Folks,
I have the low coolant warning permanently on Checked all the usual things, changed sensor but have been advised tha there could be an inconsistency in that the magnetic float in the toptank may have become detached causing the sensor to put the light on.
Anyone had this prob and is it fixable or do you have to buy a new toptank. Any advice appreciated. Charlie.

(Chris Gates (XJR 1998)) #2


If you eliminate all other possible causes for the low coolant warning and can ascertain that it is the actual level sensor/“float” switch that is the problem, then you can buy a replacement here( https://www.britishparts.co.uk/jaguar-parts-c11/jaguar-f-type-c398/cooling-heating-c504/sensor-coolant-level-p4797) for instance. Other Jaguar specialist company’s also sell them, possibly even Amazon or flee bay.



(XJScharlie) #3

Thanx for that. I already bought a new sensor. What i was talking about was the part inside the toptank that tells the sensor what the level is. Just wondered if this is a fixable issue before i take the tank off. Rgds. Charlie.

(Andy) #4

best thing to do it put your finger in, a prod the float up and down a bit to ensure it is free to move

(XJScharlie) #5

Thanx Andy thats what i’d hoped; does the float run up a guide? Will check out tomorrow. Also got a prob with the heater pump; obtained a second hand replacement which does’nt work, apparently its a common prob.

I have a spare 12v water pump very simple 5W pump that i’m thinking of installing can you see any prob in doing that as i dont want to fork out £69 for a second hand replacement from Ebay that might not work.

Sorry to be a pain. Regards. Charlie.

(Andy) #6

Yea the float has the sensor in the middle.
The float is at the front of the tank and can be seen with the cap off if the fluid isn’t high.

If your front fog lights don’t work that maybe why your pump doesn’t work. As a fuse is blown

(XJScharlie) #7

Ok will check that out . Many thanx. rgds.

(j limongelli) #8

You can cheat as the sensor was too high in the bottle.
If you jump the two wires together, it will never come on again :slight_smile:Its been done more than once.
The sensor was put in the wrong spot!.
Old water under the bridge, the Vanquish used the same bottle and sensor.
All under Ford of the time.

(XJScharlie) #9


The sensor inside the toptank was stuck in the lowest position. I freed it off and its now Ok. Rgds.