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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 22750
Experience:  BEng hons Mech engineering, in auto industry 22 years
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The disc brakes on our BMW 120i heat up even when we don't

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The disc brakes on our BMW 120i heat up even when we don't touch the brake pedal.
I tested it by driving at around 50mph for 15 minutes without touching the brake pedal (literally didn't touch it even once... it's a quiet road) and three of the discs (two rear and one front) were so hot I couldn't touch them. The other front one was hot, but not THAT hot.
I did the same route with our other car (which also has disc brakes) and it came back with all four discs stone cold!
The reason I checked the BMW in the first place is that we recently got new discs/pads on the rear and one of the calipers was stuck (the car had a resistance to rolling). Both rear calipers were cleaned/lubricated and now the car rolls freely. But now I've discovered the heating issue above.
What could be causing all four discs to heat up like that?
HelloI'd 1st check that there's nothing binding up the brake pedal, no carpet stuck or anything else that coudl prevent the pedla from returning to its stop if that's OK then I'd pull out the ABS fuse to check that its not doing anything odd and go for a short test drive to see if the disc get hot and if thats OK then I'd remove the master cylinder and have your assistant push down on the brake pedal to expose the pushrod as it exits the servo on the end of the pushrod there should be a little adjustment nut try screwing this in a turn or two and put it all back together this adjustment takes out free play at the pedal so its better to have a little bit of play rather than too tight
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