Very rough idle,

Hi I have just removed my old CTS and see there was NO water below there…I am confused…should the tail of the CTS be sitting in water to do it’s job??
Maybe the source fo my problem be that it is dry in there…??
Please advise…
Thanks, Sloth (Ivan)

Yes, your Coolant Temperature Sensor (CTS) should be immersed in coolant in order to work properly. If you removed your CTS and found air in your coolant rail then either you have a coolant leak or the last time your coolant was changed the correct procedure for bleeding air from.the cooling system was not followed. This procedure can be found in the XJ-S Repair Operations Manual (ROM), Kirby Palm’s book, or by searching Jag-Lovers archives. Essentially you have to raise the front of the car and bleed the air out of the radiator bleed ports. I recommend that you not drive your car until the coolant system is properly serviced and the coolant hoses and clamps are checked.


Absolutely correct Ivan.
Header tank should be full to the brim.
Is your coolant light working ?
If not, there is a module involved and should be investigated.
And as Paul says, find the source of your low coolant or you will lose your engine…