down a steep bank C320cdi

[robtt]

Yesterday with three passengers came down steep bank not quickly as T junction at bottom and had the devil of a job to stop.Brake assist kicked in and I only managed to stop a foot or two over white line! Car is week old C320cdi with seven speed box.It appeared to keep in 7th gear until the last few yards when it went into second with a loud clunk and that in turn made the car lurch! Is there a sotware fault on the box or is is something else? It was v. dangerous and not something I want to have repeated! Rang York Mercedes this morning but they have not rung back with advice as yet.Any thoughts ??

 

[Tan]

I would call out Mobilo, they will be alot quicker than the dealers.

If they ask is the car driveable just express your concerns that its faulty brakes.

 

[GrahamC230K]

If you were off the gas, the car effectivly free wheels does it not? Surely the gear it WAS in on an auto is irrelevant and it does not change down as you brake or am I very much out of date?

Gearbox aside, if you had trouble stopping the car from what you describe as "not quickly" you are right to be worried and had better have your one week old car inspected ASAP. I would ask your dealer to come and collect it on a lorry.

 

[jeremytaylor]

I would call out Mobilo, they will be alot quicker than the dealers.

If they ask is the car driveable just express your concerns that its faulty brakes.

Seconded.

 

[MangoMan]

Sounds like a Brake/ABS concern to me. Would be loathe to drive it !

 

[Rory]

Yesterday with three passengers came down steep bank not quickly as T junction at bottom and had the devil of a job to stop.Brake assist kicked in and I only managed to stop a foot or two over white line! Car is week old C320cdi with seven speed box.It appeared to keep in 7th gear until the last few yards when it went into second with a loud clunk and that in turn made the car lurch! Is there a sotware fault on the box or is is something else? It was v. dangerous and not something I want to have repeated! Rang York Mercedes this morning but they have not rung back with advice as yet.Any thoughts ??

What speed were you doing down this steep bank? I can't imagine that the car would have been in 7th. How would you know what gear (epecially with 7) it was in anyway?
And when you say 'brake assist', do you really mean ABS?

Sounds like you've come down a steep bank, 4 up, in a car you're not yet familiar with, and underestimated the stopping distance.

 

[robtt]

Agree I am unfamiliar with car and auto box hence my query.I am familiar with Grand Cherokee auto and it never did anything like this.I realise this is not an altogether fair comparison in the circumstances but why the sudden lurch and having to brake against the engine so hard.Yes abs did come in but brake assist did as well as car almost on its nose as it became an emergency!! I was inches away from a Golf by the time I pulled up.I was not going fast had a ninety and eighty year old in car and no more that 20mph when everything went pear shaped!!

 

[Brian WH]

Definitely a serious fault, as at that speed the car should have stopped in its own length, when slapped on. The car should read the urgent need to stop and react accordingly. The gearbox gear is irrelevant as Graham said.

 

[Shude]

The gearbox gear is irrelevant as Graham said.

If I brake very hard mine also shifts with a slight bump when close to stopping, I've never worried about it as it seems to know what it's doing. Bear in mind that when on a hill the transmission behaves slightly differently, especially on very steep hills.

 

[Rory]

Definitely a serious fault, as at that speed the car should have stopped in its own length, when slapped on. The car should read the urgent need to stop and react accordingly.

How can you say that?
Clearly we're all guessing quite a bit on the exact circumstances, but if it was a steep 'bank' then I read from that that it was not a normal steep 'road'.
Also, doesn't BAS only work if it detects a sudden, emergency, requirement to stop?
If the ABS was working then (assuming it isn't faulty) there would seem to be some problem between the tyres and the road.
Was it wet, slimy, gravelly etc? It also occurs to me that the car is very new and brand-new tyres can be a bit iffy as they still have the release agent on them (this caught me out big time once, although it was literally a mile after having them fitted).
I'm also wondering how a lurch in the gearshift would have noticeable with the ABS going like the clappers?

 

[robtt]

Got an appointment with York Mercedes on Wednesday morning to have diagnostic check.Their guy reckons a sensor not working properly.We will see...

Incident on normal if steep road/bank not a lot untoward in that.Only my opinion on bas working but I was braking as hard as poss and very quickly hard on brakes when I realised we were not going to stop in a normal manner!

 

[saorbust]

Don't forget a car 'in gear is a car in gear' and no matter what gear you will still be braking against the engine as well. Unless of course its 2nd or 1st gear, in which case the lock up converter is partially disabled. (I think - remembering the 7 speed spec's)

 

[blassberg]

the gearbox clunk is normal if its a movement rather than a loud noise. It's like it's changing down too early. I get it regularly at the first set of traffic lights after some quick runs. I select C if I want to hide that from passengers.

I think your pads were still bedding in?