Sudden deceleration while driving

knosys · 03-15-2024, 01:09 PM

I have an 2015 F80 M3 6MT with 29k miles. Recently I've notice sudden random rapid deceleration but it only happens when its raining outside. I have a 4 mile commute and it will usually occur at least once at random when its raining. When this happens I will throw it in neutral and then shift back into the appropriate gear and it drives normally again. It feels like when it detects a car in front of you and automatically applies the brakes, but there is not a notification in the HUD or dash when its happening it just suddenly starts to slow down, quick enough to throw me forward. Any help would be appreciated. Thanks

StanislavK82 · 03-15-2024, 02:14 PM

I’ve never had that happen before but I wonder if it’s brake related. I believe the car periodically applies the brakes when it’s raining to keep them dry when needed. Maybe air in the system or something else is keeping this from working normally (you shouldn’t actually notice this). It’s just an idea but next time it rains try using your wipers manually instead of enabling auto wipers. I think the system only turns on with the auto wipers.
A brake fluid flush may help, use the lv fluid since it’s thinner for such systems to work better.
Of coarse, if you’re not using auto wipers then maybe it’s something else. Hopefully this helps.

knosys · 03-15-2024, 04:02 PM

Quote:

Originally Posted by StanislavK82

I’ve never had that happen before but I wonder if it’s brake related. I believe the car periodically applies the brakes when it’s raining to keep them dry when needed. Maybe air in the system or something else is keeping this from working normally (you shouldn’t actually notice this). It’s just an idea but next time it rains try using your wipers manually instead of enabling auto wipers. I think the system only turns on with the auto wipers.
A brake fluid flush may help, use the lv fluid since it’s thinner for such systems to work better.
Of coarse, if you’re not using auto wipers then maybe it’s something else. Hopefully this helps.

Ah, that explains it. I'll try your suggestions. Thank you for the help

03-15-2024, 01:09 PM	#1
knosys Registered 0 Rep 2 Posts Drives: BMW M3 Join Date: Mar 2024 Location: Louisiana iTrader: (0)	Sudden deceleration while driving I have an 2015 F80 M3 6MT with 29k miles. Recently I've notice sudden random rapid deceleration but it only happens when its raining outside. I have a 4 mile commute and it will usually occur at least once at random when its raining. When this happens I will throw it in neutral and then shift back into the appropriate gear and it drives normally again. It feels like when it detects a car in front of you and automatically applies the brakes, but there is not a notification in the HUD or dash when its happening it just suddenly starts to slow down, quick enough to throw me forward. Any help would be appreciated. Thanks
	Appreciate 0 Tweet Quote

03-15-2024, 02:14 PM	#2
StanislavK82 Private First Class 86 Rep 137 Posts Drives: 2016 BMW M3 Join Date: May 2019 Location: Northbridge MA iTrader: (0)	I’ve never had that happen before but I wonder if it’s brake related. I believe the car periodically applies the brakes when it’s raining to keep them dry when needed. Maybe air in the system or something else is keeping this from working normally (you shouldn’t actually notice this). It’s just an idea but next time it rains try using your wipers manually instead of enabling auto wipers. I think the system only turns on with the auto wipers. A brake fluid flush may help, use the lv fluid since it’s thinner for such systems to work better. Of coarse, if you’re not using auto wipers then maybe it’s something else. Hopefully this helps.
	Appreciate 0 Quote