Drove to work this morning at a sensible pace without any hard braking and for some reason I thought I would feel the brake discs when I got out. All the brakes were warm with the rears warmer than the fronts. Say what? Why would the brakes be anything but just slightly warm? The road outside work is 45mph and well policed, so I was not going fast nor am I a hard braker unless I have to.

Could it be that the parking brake saw little use by the previous owner and now it is binding.? Whatever is going on, me no like it.

 

put the car in neutral and try to push it. should roll pretty easily on a level surface. If the parking brake is binding, you'll notice it.

Heat in brakes is not a bad thing. You're still stopping 4000lbs. And the front brakes are larger and better cooled/ducted for air flow -- they'll dissipate heat more rapidly than your rears.

 

FWIW
I measured my 05 XJR brake rotors with an Infrared Thermometer and got 100 to 105 Degrees F after gentle run at 70 degrees ambient.

These were Brembo brakes but I doubt there should be much difference between a Brembo XJR and an 07 and up XK.

 

Well, ambient yesterday morning was about 45°F and the rears were hot enough to make me look for a burn mark on the back of my knuckle. I would guess the rears were at 150°F+. When I backed out of my space I knocked the car into neutral and it seemed to coast OK. The dealer is going to look at it tomorrow.

 

Brake disks will get hot - very hot.

They are converting all the energy of your car moving into heat. They'll certainly burn your hand if you touch them just after using them. So long as they are not glowing red, or boiling the brake fluid, or binding when in neutral, I wouldn't worry.

 

Just encountered a Service bulletin (JTB00084) "Parking Brake actuator" that lists "Electric parking brake fails to release properly (brake drag)" Thought of this post when I read it, and dragging would certainly keep the rotors hotter than normal (I assume the paring brake is to the rears only?)

Anyhow just thought Id pass that on as a remote possibility.

Vince

 

Many thanks. We did a couple of coasting runs in the car park and found that the car rolled just fine with no undue drag. I also found that the same trip in my SUV gave similar results re brake temps.

I also had a word about the 1300rpm growl. The word from the 30 year experienced mechanic was not to attempt the TSB fix as all it did was move the noise to a more inconvenient part of the rev band. I shall treat as a feature, not a fault.