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Emergency stop, engine revving high, possibly fighting against brakes |
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jamescarruthers
 
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   Member No: #1548
Location: Cambridge |
Correct me if I'm wrong here but after doing an emergency stop the other day, I was rather disappointed in the car's stopping performance and what the engine seemed to be doing just as I stopped. I could just be confusing unknown slippy road for poor C6 performance. FYI the front pads are genuine Citroen and have maybe 2000 miles on them, the road looked dry, tyres are Kumho cheap [%*^#@!] that came fitted and I can't wait to get worn out and replaced with Michelins. After taking considerably longer to stop than I'd have thought, I could hear the engine revving away and looked down to see the rev counter at approx 2000 rpm, even though I was completely stopped. It dropped to idle in a second or two. This is the main thing that worries me. Was the engine fighting against my braking efforts? Is this normal behaviour in an automatic car? I suppose the road could have been slippy and the ABS might have been kicking in without me knowing it, this would account for the pretty woeful stopping distance. Does modern ABS make the pedal go all vibrationey like the older stuff does? MOT next week so I'd be pleased to compare brake force readings from my car to some others. Any views much appreciated! |
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e3steve
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 Member No: #1163
Location: Warsash, Hants & Palma de Mallorca, Spain |
Can’t say I’ve ever felt or had a problem stopping either of mine, although the later of the two cars pulls up with noticably less pedal pressure, owing to the bigger front rotors. | ||
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jamescarruthers
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Member No: #1548
Location: Cambridge |
Might be brave and have another go on a quiet road sometime! | ||
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Dan595
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  Member No: #299
Location: Wiltshire |
Can't comment on automatics but I have had cause to do a couple of emergency stops over the years. Although in normal use the brakes can seem languid, when the emergency brake assist kicks in the car almost stands on its nose. Might be worth checking front brake slides - both of mine have had to be changed. |
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PIT
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  Member No: #2671
Location: Sofia |
Is it possible to be intended behavior? The brakes use vacuum to operate the servo, so in emergency situation it might keep higher RPM of the engine to ensure that there will be good vacuum from the vacuum pump. | ||
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MGmike
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 Member No: #3151
Location: South Queensferry |
No, not normal behaviour. A car usually has move vacuum in the inlet manifold at idle than at 2k rpm. To sustain these revs air needs to be getting in somewhere and if it is the vacuum will be lost. By all means try a quiet road to see if the fault is repeatable because if it is, it should be easy to tell when it's fixed! good luck |
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eduardomaio
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 Member No: #869
Location: Lisbon |
I have done some emergency braking and even tested on a quiet road to see if the hazards would come on when I first got the car. I can't remember in any of those situations the engine revving high, usually the revs die down and you are idling normally when the car stops. |
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vaho
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  Member No: #2228
Location: Tallinn |
I would be worried about the engine revving, it is not normal and should not happen in any circumstances. One of the possible causes of diesel engines revving uncontrollably is when it starts burning the oil. If it´s happening during normal operation there is an oil leak big enough to feed the intake and then there is not much to save. In your case it may be that the oil that was already in the intake system (intercooler specifically) and got moved during heavy braking and some of it managed to make it´s way to the cylinders to burn and cause the revving. This is my opinion and I would check possible oil leaks into the intake system (turbo seals and crankcase ventilation system are the usual suspects). |
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C6Dave
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  Member No: #1
Location: Northumberland |
vaho wrote ... I would be worried about the engine revving, it is not normal and should not happen in any circumstances. One of the possible causes of diesel engines revving uncontrollably is when it starts burning the oil. Similar issue to the C4's whereby leaking injector seals let derv into the sump, letting the oil become diluted and the volume increase until the oil gets sucked into the system and the turbo runs away uncontrollably. You need to get the car checked out, have a look at the oil via the dipstick for starters |
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jamescarruthers
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Member No: #1548
Location: Cambridge |
Fear not its a petrol car and it runs absolutely perfectly! | ||
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vaho
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Member No: #2228
Location: Tallinn |
My bad, I assume every time that all C6-s are diesel, need to read more carefully next time. | ||
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PHaTGRoB
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 Member No: #994
Location: North Wales |
I've noticed that you have an LPG system fitted. Were you running on LPG at the time? I used to have an Ford Explorer 4 litre with LPG system and it used to do odd things every now and again when running on LPG that it didn't do when running on petrol. Worth getting that system checked? I also use to run a Ford Granada Scorpio many years ago. I fitted cheaper tyres to it at one point, after which the ABS was always cutting in. ABS will increase stopping distance compared to an old-fashioned skid but allows steering control whilst braking. Anyway, after changing to Goodyears the ABS was rarely activated and this is the reason that I don't fit cheap tyres. | ||
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C6Dave
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Member No: #1
Location: Northumberland |
vaho wrote ... My bad, I assume every time that all C6-s are diesel, need to read more carefully next time. Me to.... |
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cruiserphil
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 Member No: #38
Location: Celbridge |
James, Just one to watch - I was braking sharply for traffic lights that changed as I approached and got the engine revving effect. What I found was that I was wearing a new pair of safety boots and was catching the edge of the accelerator pedal with my foot when pressing down the pedal lower than usual. It caused the car to push against the brake. It was scary. It happened me again and now I can't risk wearing those boots when driving C6. It doesn't happen under normal braking because the pedal is not being pushed low enough. Best regards, Phil C. |
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Tjensen
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 Member No: #954
Location: Bergen |
Big boots are not for driving, the C6 is not a special problem here. Small cars and big boots are dangerous. I found some Swedish shoes "Made for the Pleasure of driving" (!), but generally good classic gentlemen's full-leather shoes are good. | ||
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