HBC350

I was surprised the first time I sat on a hill in my '08 C350 and the brakes of the car held the vehicle in place. Never had a car with that feature before.

Recently, I have experienced intermittent instances where the car's brakes hold it in place (you can tell the feature is activated because the pedal is rock hard and the vehicle doesn't creep when you let off the brakes) even when I'm on level ground. Anyone else? It makes take-off herky jerky and I don't like it.

peabers

Hi and welcome to the forum.

I have experienced the hill assist on inclines upwards of 20-degrees. You know its working because you let go of the brake pedal and the car stays in place (whereas other cars would start rolling backwards).

I have never had an instance where the brake pedal has become rock hard though. The hill assist is an electronic system and doesn't affect the pedal position afaik ... unlike some cruise control systems where the gas pedal would be held down.

Perhaps something to check with the dealership?

len56

I don't have the car... but that doesn't sound good. I really wouldn't want that...

is there a way to shut it off worst case scenario? (if they can't fix it)

HBC350

My guess is that the hydraulic brakes are electronically actuated by the system and that's why the pedal is hard. I'll mention it to the dealer so that I can hear them say no problem found, unable to duplicate, operating to manufacturer's specifications. I haven't heard those words in a while and I sort of miss them. :-)

GateKeeper

I have had the rock hard feeling of the brake pedal in the past and can replicate it at will

If your on a hill and stop, and then release the brake pedal, and before the car's hill assist feature release's you hit the brake pedal again, it will become rock hard as mentioned, I don't think it's a flaw, but since the system is "under pressure" trying to push more brake fluid is not possible, and the rock hard feelings occurs....

Well I at least think this is why......

GK

joshg1001

yes the rock hard is part of it. you were probably on some sort of incline that was just a bit less level

HBC350

I get why and how it happens. I just don't think it should happen when I'm stopped on level ground. One of the few flaws I think exist with my car. Other than two sunroof failures, two shots at correcting a drift to the right and an annoying buzzing from the instrument cluster on less-than-smooth roads the car's been flawless.

C300Sport

Sounds pretty normal to me. Anything over a 5% grade will activate the system. If you let off the brake and then depress it again before the system times out and releases the brake, the pedal will feel rock hard. Anyhow, with a manual, it does make takeoff a little harder to modulate, but you will get used to it pretty quickly manual or automatic.

HBC350

Nope. Absolutely level ground. No way I needed hill assist.

C300Sport

May have a faulty inclinometer. I would take it in for service...just in case it is trying to brake at other times as well...like on the freeway.

peabers

Brake lights come on when Hill Assist is active, I believe. So you should be able to validate this.

HBC350

The problem with that is theory is that I am on the brake pedal when it happens so the brake lights should be on. My complaint is that the hill assist engages when stopped on level ground and the car has a jerky acceleration from a stop when this happens. When you lift off the brake pedal the car remains stuck and only releases a split second after you apply the gas. That split second is an abnormal one.

kaku

are you sure you're on level ground? if i remember reading correctly (off the driver handbook), i believe the hill assist will initiate on an uphill slope of 5 degrees or more..

GateKeeper

if the above is the case, and your on level ground and it engages, then for sure take it in and have it checked out......

mine has never done this.....

very odd indeed....

HBC350

Certain. No detectable grade whatsoever.

kaku

perhaps the angle sensor has gone amiss..

as GateKeeper suggested, i'd take it in to have it looked at.

cvkatigbak

no problems here with MT. i love it, the gas pedal is so far that it makes it easier being on steep hills rather than having to catch the gas.

cvx5832

I'm a bit late but for what it's worth, the system has worked for me very well so far. Only engages on an incline, and never holds the car back when you're already on the gas pedal. 26k miles and it's a pretty transparent system in my opinion.

My wife's BMW has this issue. It doesn't catch everytme, but when it does it is quite annoying. The only reason I haven't taken it in is because I don't really drive it that often.

Good Luck,

Paolo

joshg1001

after driving me car for a long period of time today, it occured to me that it just might be the transmission. its always been jerky in terms of down shifting especially in gear 1 and 2. Its slow to shift when you are braking almost to a stop and you accelerate again. you get that split second jerk