cruise control not disengaging

bmwguy

a friend of my fathers recently wrote off his 3 series bmw, E46, (not sure of which year or model but would guess at 2000) because he could not disengage his cruise control, whtever he tried. i dont know what measures he used apart from the obvious, but he would be a competent guy, knows a bit about his motors mechanically and would not be a messer in the car. it must have been a while though, because he warned his passengers about the impending crash well in advance. luckily nobody was hurt but has anyone ever heard of this happening before on bmws or indeed any other cars, i have cruise control on my 5 series but want to be assured this is definetely a one off before using it again!

Zube

bmwguy wrote: »

a friend of my fathers recently wrote off his 3 series bmw, E46, (not sure of which year or model but would guess at 2000) because he could not disengage his cruise control, whtever he tried.

Wow, cruise control disables the brakes!

h3000

Why did he not switch the engine off

Mr.David

Probably a faulty brake light switch, which would normally over ride the cruise control.

bmwguy

would switching the engine off not make you lose brakes and steering though?

Mr.David

You would loose all assistance. Was the car manual or auto?

ageary08

Seems illogical to me that somebody would wire something as crucial as cruise control in series with something that is liable to fail. Thats a scary story, but was it case of the driver panicing or are there so few safetys on a cruise control system ?

h3000

bmwguy wrote: »

would switching the engine off not make you lose brakes and steering though?

You would lose power steering but you could steer the car without too much bother and breaks would need a bit more effort but they would stop the car. I presume if he was using cruise control at the time it was a reasonably big open road.

bmwguy

not a motorway but a 100 km/h single carriageway. he came to rest eventually on a grassy bank and a fence so nothing too damaging but a serious enough incident all the same. car is finished anyway.

Zube

Mr.David wrote: »

Was the car manual or auto?

Had to be an auto, or the driver could just tap it into neutral.

Mr.David

Zube wrote: »

Had to be an auto, or the driver could just tap it into neutral.

True. But if its an auto then surely you cannot turn off the engine at speed, you would have to put it into 'park' which you cannot do when moving. **** situation

Alun

Also on a manual, depressing the clutch will disengage it (at least it did on the one and only car I had that had it).

Mr.Diagnostic

Did this happen in the west of Ireland by any chance? Would the car have been an E39?

Zube

Alun wrote: »

Also on a manual, depressing the clutch will disengage it (at least it did on the one and only car I had that had it).

I can't see cruise control beating a full on stomp on the power brakes, regardless. This guy is cruising on a dualler, so he's in top at low revs. He stamps on the brakes and keeps the foot down, what's the cruise control going to do, drop 3 gears and rev to the redline?

Will a BMW on CC shift out of top on it's own if you reach a hill? Drop several gears?

Alun

Zube wrote: »

This guy is cruising on a dualler, ..

According to a later post of his he's on a 100km/h single carriageway road. Wouldn't be my choice of place to have CC engaged TBH.

Zube

Answering myself via Google, it appears so:

When driving up-hill, it can be necessary to change into a lower gear. ACC does this automatically.

and:

If necessary, ACC will change to a lower gear in downhill driving to minimize wear on the brakes and ensure that a constant distance is always kept.

So at least some BMW cruise control systems will change gears if they feel like it..

traco

Never heard of such a thing happening, brakes should disengage cruise control as a safety feature but thats not to say it didn't happen

I would imagine that on any car where cuise control could stay on there would be a full mandatory safety recall by the manufacturer.

Cruise control will downshift if required and will accelerate very quickly if you hit "resume" and there is a large speed differential to be made up.

On my cruise control I could swear it actually brakes the car - for example if i come to the end of a motorway and it was set at 120kph and I drop it to 100kph it slows down much quicker than if I disengage it and coast.

bmwguy

traco i think you're right about the mandatory recall - if thats what happened. good to hear most people dont believe me that it was the cruise control - i'll continue to use mine so as it is a feature i like.

Zube

traco wrote: »

On my cruise control I could swear it actually brakes the car - for example if i come to the end of a motorway and it was set at 120kph and I drop it to 100kph it slows down much quicker than if I disengage it and coast.

Yes some CC systems will apply the brakes, especially the adaptive ones which watch the gap to the car in front.

bmwguy

mr diagnostic,

the car was an e46 and it happened in the south east

Mr.Diagnostic

bmwguy wrote: »

mr diagnostic,

the car was an e46 and it happened in the south east

Well, thats the 2nd I have heard of so.

Balfa

For future reference, pressing the clutch, or putting it in neutral (even in an automatic - and it is possible to switch the engine off, you don't have to be in "park") will disengage the engine from the wheels, preventing this from being a problem.
I encourage people to experiment with their car during daily driving. It keeps you concentrating on your driving and helps you be more comfortable and reassured when a hairy situation does arise.

Mrs. Balfa isn't even certain how to turn on the main beams, ffs

milltown

Wasn't there one in the UK a few years back too. The guy said his throttle stuck open or something and rang the AA and the police while his car dragged him flat out along the motorway. He cooked his brakes completely and ended up crashing into a roundabout. I think BMW investigated at the time and couldn't see how the chain of events he described could be possible.

I know it's counter-intuitive but if the brake switch does fail, pressing the accelerator will also disengage the cruise control. I'm pretty sure that the transmission lock doesn't prevent shifts from D to N on the auto box. I'll check on my way home in the morning.

Balfa

milltown wrote: »

I'm pretty sure that the transmission lock doesn't prevent shifts from D to N on the auto box. I'll check on my way home in the morning.

As I explained just above, it doesn't. The only lock I've seen is on some cars (BMW, for example), it won't let you shift from N to D without applying pressure to the brake only if the car's stopped. Once you're moving, you can shift freely between the two.

I know it's counter-intuitive but if the brake switch does fail, pressing the accelerator will also disengage the cruise control.

For most cases, this is untrue. In normal operation, if you accelerate from a cruise-set 60mph to 65, then release the throttle, it'll settle back to 60 and continue at that speed. Again there are exceptions...

BMW has a timer. If you accelerate and keep it at 65 for over a minute or something, it assumes you've forgotten about cruise control and disengages it, so that you're not surprised by it kicking in when you drop back through 60mph.

dingding

I remember the UK story also.

Guy:Incognito

dingding wrote: »

I remember the UK story also.

Did it not turn out to be all lies to cover up being 2 or 3 times oer the limit or some such ? Maybe I'm thinkiing of a different case.

Howib

Driving today in my wife's 2008 5 series doing 80mph in cruise control on moter way pressed brake brake went to the floor- cruise control didn't disengage blew cars off the road- they must of taught I was crazy - brakes then slammed on making me loose control then as quick brakes went again and car started speeding back up to cruise control speed- switched off car but bein panicked took foot off clutch car restarted an whole process started again- switched off car an let it coast to side of road- people stopped to see what the hell was going on BMW will have a lot of questions to be answered Tuesday morning any taughts!

ninty9er

I'm having the opposite problem, trying to get it to remain engaged!

serious3

brother in laws 2008 mondeo did the same late last year, he hit the end of them m6 motorway roundabout and vaulted the armco and ended up upside down with my sister in law having to be cut out of it with a broken pelvis and cracked ribs. ford took the car away from the impound and he's been told its still being investigated. symptons were the same as what you describe, pedal hit the floor and kept going at 120kmh, he panicked and admitted such to the guards and didn't know what to do.

goz83

I'm thinking this thread is 28 months old and you should have started a new one.

Our man in Havana

FFS! Do not resurrect zombie threads.