[jonfon26mk]

Hey all,

I recently purchased a 2013 M135i with 14k miles on the clock. I absolutely love the car so far! However...

When it rains, the car decides to apply the brakes roughly every 30 seconds on its own. I wondered if this was just the brake drying feature they have, but from what I have read, that feature is supposed to be "un-noticeable" Mine is DEFINITELY noticeable and slows the car by over 5mph when on cruise control. Very frustrating when trying to regulate speed on the motorway! The brakes appear to bite for about 1-2 seconds at a time and during this time, the throttle is pointless.

The problem occurs with or without cruise control activated and happens in any of the driving modes (Eco/Comfort/sport). It even happens with the auto wipers turned off!

As soon as it's dry though, it's 100% fine.

Doe anyone know what this could be? I'm scared that it's something dangerous that is suddenly going to lock the brakes in the fast lane of a motorway, or something that's going to be un affordable to fix, like the hydro unit!

Any suggestions would be more than welcome!

Thanks,
Jonathan

[thakid22]

Something is definitely amiss here.
Brake drying should be active only when the windshield wipers are on.
Is this happening even without the wipers on? Turn the wipers on in dry conditions. Do you still get the pulsing?
You really should not feel it at any point.

This is a safety issue. I think you may have a DSC malfunction of some kind. If it gets worse, who knows what it will do and when.

Throttle cut during the brake grab? What does the rpm gauge do? Does this happen during a specific rpm range?

Bad speed sensors and/or faulty DSC modules can cause these problems you experience. Take it to BMW right away as you should still be under warranty. Get a loaner car too!
The potential danger of the car erroneously applying the brakes is not something to take lightly.

Just curious... Any aftermarket electronics in the car? Cell phone? Radar detector? If so, take them out and see if the car still has the problem.

Don't think you have to wait until it rains again to demonstrate this to your service center.
If Brake Drying is causing your problem, it should still do it in dry weather IF you have the wipers on.

If the issue is truly only repeatable in wet weather, water may be getting somewhere it shouldn't. Let me know what you find.