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Dangerous fault: rapid braking when raining?

7K views 11 replies 9 participants last post by  iankshaw99 
#1 ·
Hi all, have a very scary and serious fault with my 2014 116. As soon as it starts raining if I'm doing over approx 40 mph, the car brakes intermittently and very harshly so I rapidly lose speed. If there was a car behind me, there is no doubt they'd go into the back of me. When it happens, I am driving normally, the brake pedal doesn't move and I am not pressing it and I doubt that the break lights go on to warn any drivers behind me. It ONLY happens when it's raining. I put it in the garage and they said there was nothing wrong with it but it's just done it again on the motorway. Help!
 
#2 ·
To explain a bit more: if I were driving at 60mph, it might suddenly and rapidly decelerate for a few seconds then return to driving normally. Some time within a few minutes it would then do it again and it would continue to do that while it was raining and I was driving above 35-40mph.
 
#3 ·
Hi SDG.

Ours is a 116i sport and is doing exactly the same thing. Not harsh breaking but decelerates for a few seconds then returns to normal. Been back to our dealer 3 times with NO explanation. Do you have Comfort/sport button on centre console? Have you tried it in sport mode?

It's going back Tuesday again so will let you know if any news.
 
#4 ·
This is a feature known as brake drying, I'm not 100% on how it works but the idea is that it lightly applies the brakes when it's raining to keep them dry. It seems that it's a bit over keen though and people post reports of it really braking hard for seemingly no reason.

Have a search for it, and I guess kick up fuss with the dealer?
 
#6 ·
Nope, think the brake drying is an occasional automatic feathering of the pads to disc so any water film has no effect when wanting to brake and reduce speed, came in.... ages ago cos recall it since I started with bmws, so since 2001 perhaps, the old tech was with wet discs would hesitate on initial braking...

Sounds like the standard brake drying 'thing' is being a bit over active, do wonder how adjustable it might be, shimmed perhaps in some way. diff washers maybe, surely can't be out of a decent BMW dealers to sort?

The other alternative could be fancy collision avoidance package deciding too close to the car in front, it's out there already.......


Water into brake fluid might bugger up seals as well, though unless through the top-up filler the whole thing about brake fluid under pressure would I imagine make it quite difficult......

My betting is it's up to BMW to sort out, it's clearly a safety issue, even if it means new callipers......

Good Luck!
 
#7 ·
Nope, Sounds like the standard brake drying 'thing' is being a bit over active, do wonder how adjustable it might be, shimmed perhaps in some way. diff washers maybe, surely can't be out of a decent BMW dealers to sort

So the millions that BMW engineers spend to create and design a car are wasted when a decent dealer can shim in some diff washers??

Is that a real reply??
 
#8 ·
I have just been through this exact same problem. We tested driving it with no rain but with the wipers on and it did the same braking issue, harshly. We then disconnected the rain sensor from near the rear view mirror incase it was an issue linked with the sensor, and the issue reoccurred. We then turned traction control off to deactivate the dsc to try and see if it was an issue with the dsc, and it continued. I then found a website in UK called ecutesting and they shown videos of this common fault on 1 series between 14 and 19, and said it’s an ABS issue. I had a mechanic take the ABS unit out and send it to this company, they found the fault, fixed it, and returned it to me. The issue now resolved. The fix cost me £260 from ECU and I paid a mechanic £150 to remove the part, refit it, and bleed all the breaks after as this is a part of the process. Hope this helps.
 
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