It's starting to get cold here in Texas and I noticed that I get no heat when idling, lukewarm heat from 30-50mph, and decent heat from 65mph up. I bought an instant read thermometer to see what the numbers were. 30-50mph 80-90 degree Fahrenheit and then at 65mph up its 120 degrees Fahrenheit. I did some googling and it looked like it could have been a clogged heated core so I did a back flush on the heater core. When I did the back flush I noticed the coolant coming out of the heater core was fresh clean coolant so it seems it must have not been clogged. The only other bits of evidence I have is when I run the car with the coolant car off bubbles come up I don’t know if that’s normal and I have to keep adding a bit of coolant to the reservoir every week. Any ideas of what my issue could be?

-P.S. I know in the manual it says that if the low coolant light is on you won’t get any heat. All of this heat testing has been done with now warning lights on the dash.

 

https://www.jaguarforums.com/forum/x...em-xj8-192877/

 

As per the other recommended thread, searching this forum really helps.
The bubbles should be ok if the engine is running, cause the coolant is pushed around in the system.

How high do you fill the tank?
If you always fill t othe neck you will see the level dropped after a ride (cause it is pushed out by the system to the secondary tank).
Mine settles some inch below the neck, if it keeps dropping further, you have a faulty cap or a leak.

 

In is link you will find reference to the 33A motor brush replacement ( the SC engine has the same motor for the intercooler if your in a pinch ) :

https://www.jaguarforums.com/forum/x...em-xj8-192877/ see reply # 12

http://store.eurtonelectric.com/brus...tage33e-2.aspx

https://www.jaguarforums.com/forum/x...3/#post1795189 see reply # 2453

In this other link you will find reference to the engine speed overriding the heater pump phenomena : The X300 and X308 have the same system

http://jimbutterworth.co.uk/8jagpump.htm

You can tap on the pump with a broom handle and get it to spin as a way to know if the pump repair will resolve your issue . But then by it not spinning is not proof that it will not resolve it .