2018 XF 2.0L deisel AWD 14000km. LHD
Under adaptive cruise control at more than 50km/hour, as the brakes are applied to maintain distance, a noise like "brrrr" comes from the left front brake. Only as the brake is applied. Actual braking is fine, no pull on the steering. Normal braking is excellent and no noise occurs. Jaguar dealer, in Limoges France, can demonstrate the problem but cannot offer a solution (not too surprised by this) even though they messed about with the car for 3 hours. They said they will check with Jaguar France to see if there are other cases happening. The car was originally registered in Germany in November 2018 but ended up in France where I bought it 3 months ago with only 7000 km (just over 4000 miles) on the clock so, evidently, it has sat around not driven for some time although all systems are fine and it drives very well. Sooooo, any suggestions?

 

Your description of the sound is like the ABS is activating.

 

Thanks. The service guy at the Jag dealer suggested that but neither of us could see why it would happen on only one wheel and, we assumed, that if the ABS were activating it would brake that wheel very strongly compared to the others perhaps inducing a "pull" to that side. It doesn't, the car brakes very smoothly to reduce speed behind a slower vehicle.

 

It may be because it's actually activating on both front wheels even though it sounds like just the one nearest your ear. That's the side the ABS unit is on and where the sound comes from? Just guessing here.

 

That's an interesting thought. You think the noise might be coming from the ABS unit not the brakes? Because the car is braking I naturally thought the noise was coming from the brakes. Will try to get this checked out.

 

That "brrr" sound is like what the ABS control unit makes when it pulses the brakes. It would be strange that it only does it during Active Cruise Control though but that's the sound. If you've ever driven on ice you'd know what that sound is. I'm wondering if it does it on purpose to slow the car gradually instead of brake/accelerate/brake etc. while following drivers that constantly change speed and making it uncomfortable for you.

 

So I just bought a 2020 model XE and, under automatic braking, the same thing happens. A noise that I originally thought was coming from the brakes is definitely coming from the ABS unit on the driver’s side (LHD) but not nearly so loud or obvious. So, there it is. It’s probably a normal noise, but a bit disturbing.

In another incarnation I was at the US Embassy in London when Cadillac delivered a new fully armored vehicle for the ambassador. Very heavy. but plenty of power. However, the people that armored the car had “forgotten” to adjust the ABS initiation point so that, at low speed, with no hard braking the ABS would come on and cause the car to stop suddenly. Very annoying. I don’t know if the problem was ever fixed.

 

Thinking about this........ there would be no way to regulate the braking automatically so it just slows a little to maintain distance without developing a whole new system that reacts proportionally. Pulsing the brakes gets the job done without extra hardware. And stuhillman helps verify that instead of being a problem it's probably a feature..