05 2.0HDi Lumpy Idle, Stutter and a few other bits - XantKing
Got a few niggly problems with my 112k mile C5 - it's an 05 plate 2.0 HDi - the facelifted version of the MkI C5 with the 136bhp engine.

Firstly, from a cold start, the brakes sometimes have no pressure for a minute or so. The STOP light on the dashboard doesn't come on when this happens, so I have no warning and have started having to test the pedal for firmness every time before pulling away to check. Are the brakes run from the same pump as the suspension hydraulics on this particular Citroen? Any ideas?

Secondly, and these may be related - the idle is occasionally slightly lumpy, nothing huge, just a minor erratic vibration I can feel through the controls. And at lower speeds, the car has a tendency to stutter very slightly under acceleration, most noticeable in 1st and 2nd as you emerge from junctions or pull away from lights.

The car has a full Citroen service history, and I had the FAP and its fluid renewed about 10k miles ago in August last year - the stutter was present before and after this was done. Oh, and sometimes, when accelerating hard in the dark with cars following behind, I swear I can see smoke! Is this normal for a diesel fitted with a particulate filter?

No diagnostic warnings appear on the dashboard at any point for any of the above problems.

05 2.0HDi Lumpy Idle, Stutter and a few other bits - RichardW
The brakes on the C5 are conventional, so any loss at startup is serious and needs immediate investigation. Perhaps the vac pump is shot.

Re the rough idle what do you run it on? Try one of the premium fuels and see if that improves things. Other than that, it needs to go on a diagnostic computer to check the rail pressure, and then perhaps a leak off test on the injectors. Any starting problems?
05 2.0HDi Lumpy Idle, Stutter and a few other bits - XantKing
The brakes on the C5 are conventional so any loss at startup is serious and
needs immediate investigation.


I thought that. Damn and blast! Will have it looked at when it goes in for tyres next week.
Re the rough idle what do you run it on?


Ordinary diesel, but never supermarket brands. Would it be worth trying a bottle of one of the various diesel additive treatments out there?
Any starting problems?


Nope, seems to be fine with that regard.

Had a problem with my previous HDi Xantia which I stupidly threw money at without ever getting to the bottom of, most definitely don't want to do likewise this time without a jolly good idea of how to identify what's wrong!
05 2.0HDi Lumpy Idle, Stutter and a few other bits - steve_earwig
I thought that. Damn and blast! Will have it looked at when it goes in
for tyres next week.


I agree with the "needs immediate investigation", but if you're happy driving with faulty brakes... I'm guessing you have a similar set up to my 406 HDi, the engine also uses vaccuum to drive various controls, you probably have 3 vaccuum solenoids on your bulkhead, one of these controls the egr valve, I'm not sure if these are normally open or closed but when they're stuck open the car will smoke. Another controls something called an air dozer on the inlet, which runs in conjunction with the egr to control emissions.Ooh yes, another reason to get it checked out soon, this is all probably killing your FAP.
05 2.0HDi Lumpy Idle, Stutter and a few other bits - XantKing
So a fault with the vacuum pump could be behind all of these issues?

I'm not using it terribly much between now and it going in for tyres, and wouldn't at all if there was even a hint of brake problems once they had pressurised after a few minutes.

But this is what puzzles me - why the fault with the brakes is only apparent for a minute or so after a cold start and not at any other time?
05 2.0HDi Lumpy Idle, Stutter and a few other bits - steve_earwig
I'm thinking maybe you have one fault that's affecting two things, rather than 2 individual faults but, as you point out, the vacuum builds up after a while so perhaps not.

I've never had one to bits so I don't know what goes on inside a vacuum pump but I'm guessing weak seals mean it takes a little time to build up vacuum.

Here's a wild guess - perhaps one of these solenoids is leaking and once the car goes to closed-loop it's not an issue (look how many straws I have now), you could try firing it up and having a listen under the hood.
05 2.0HDi Lumpy Idle, Stutter and a few other bits - XantKing
Small update - I've pretty much stopped using the car because until I have a definite idea of what the brakes problem is, then I'm not going to spend 300 quid on tyres - I'd rather just bang in into an auction and cut my losses.

I'm starting to think that the vacuum thing might be right - I don't really know how vacuum systems work, other than they are powered by a small pump attached to the engine somewhere. Would I be right in thinking that this is a sealed system, and should be even when the car is switched off?

In my case, then, the seal is perhaps compromised somewhere, which is leading to the vacuum failing, which gets worse over time when the car is switched off? This would explain why the brakes are fine if it's only been sitting a few hours, but take longer to work the longer it's left after that, because the vacuum pump is having to work harder to reinstate the vacuum?

How complicated is a vacuum system, and how easy is it to check it for leaks?

Edited by XantKing on 28/02/2009 at 16:51

05 2.0HDi Lumpy Idle, Stutter and a few other bits - J Bonington Jagworth
" the vacuum pump"

Is there such a thing? I would have assumed that the vacuum was derived from the inlet manifold, and so a leak there might also account for the lumpy running. If you haven't already, check the brake fluid reservoir. If you're not losing fluid, then it may just be the vacuum assistance (which may just be a leaky/disconnected pipe, even if there is a pump).

Edited by J Bonington Jagworth on 28/02/2009 at 19:13

05 2.0HDi Lumpy Idle, Stutter and a few other bits - steve_earwig
There is a pump, diesels don't develop enough vacuum all the time to use the manifold vacuum like a petrol. They're usually on the end of the cylinder head, where you'd expect to find a dizzy...
05 2.0HDi Lumpy Idle, Stutter and a few other bits - J Bonington Jagworth
Thanks, Steve - I didn't realise that. I guess forced induction reduces the vacuum effect somewhat!
05 2.0HDi Lumpy Idle, Stutter and a few other bits - jc2
You get negligible vacuum on a N/A diesel let alone a T/C.
05 2.0HDi Lumpy Idle, Stutter and a few other bits - XantKing
Slight update:

I've been doing a bit of digging around, and the good folks over at the French Car Forum pointed me to the VOSA recall site. I had previously spotted in the car-by-car breakdown on this site here that some C5s were recalled to sort out an issue with reduced brake performance, but my car was not within the VIN range.

Having checked this recall on the VOSA site, it now seems that a second set of VIN numbers has been added, which DO include my car. It sounds exactly like my problem (below spec vacuum pump reducing braking performance, solution is to replace pump) and there's also an another similar recall which also includes my VIN which describes my problem - stiff brake pedal requiring replacement of vacuum pump valve.

Both these recalls are dated early 2008, when I suspect my car was in ownership limbo between coming off lease and going through the disposal process, and the last service pre-dates this too, being in Nov 2007. So it's just possible that one or other of these recalls has not been carried out to my car - which would be a bonus as presumably it would be free?

Anyways, I shall call my local Citroen dealer tomorrow and enquire if they can check. If the work was never done, it's a bit of a disappointment that it was with them for FAP replacement sometime around Aug 08 and they never flagged the problem them.

As ever, I shall report back in the hope it helps someone else out in the future. For reference though, the recalls in question are below:

Reference : R/2008/017
Manufacturer Ref : YER
Make: CITROEN
Model : C4 & C5
Launch Date : 05/02/2008
Numbers Involved : 520
Build Start Date : 06/07/2005
Build End Date : 07/07/2005

Recall Details
Concern : POSSIBILITY OF REDUCED BRAKING PERFORMANCE
Description : It has been identified that, vehicles fitted with 2I HDI engines may have been fitted a vacuum pump which may not be to specification. This could lead to a decrease in braking assistance.
Remedial Action : Recalled vehicles will have the vacuum pump replaced.
Vehicle Id : VF7******76602542 to VF7******76701556 [<- this is the set of VIN numbers not currently mentioned in the car-by-car breakdown]
VF7******74299142 to VF7******74459012


Reference : R/2008/051
Manufacturer Ref : YES
Make: CITROEN
Model : C4 & C5
Launch Date : 06/05/2008
Numbers Involved : 2557
Build Start Date : 31/03/2006
Build End Date : 03/01/2007
Concern : THE BRAKE PEDAL COULD BECOME STIFF THEREBY REDUCING BRAKING ASSISTANCE
Description : The brake pedal might feel stiff and the braking distances extended as a result of a defect in the vacuum pump.
Remedial Action : Recall the vehicles that are likely to be affected to replace the valve in the vacuum pump.
Vehicle Id : VF7******74459011 to VF7******76796753
VF7******74459011 to VF7******76796753

05 2.0HDi Lumpy Idle, Stutter and a few other bits - XantKing
Another update:

Emailed Citroen UK, who told me that my neither of the above recalls applies to my vehicle, despite my VIN number falling into the range of both of them - guess I don't qualify on account of my car having an earlier build date (it was registered March 05).

I do still find it something of an odd coincidence that it seemed to be this very fault I was experiencing, and wondered if perhaps the duff vacuum pumps were more widespread than they thought? Be interesting if any other cases on older cars turn up on here...

Anyways, I was quoted 175 quid for supply and fitting of a new vacuum pump, although there was no guarantee that was the problem. Since that was actually far cheaper than I had feared, I gave the go ahead.

Glad to say, it seems to have worked a treat. The brake pedal is soft even before I start the engine, which suggests to me that the pump itself had some kind of knackered seal which allowed the vacuum in the system to fail over time as the car was parked.

Also, the stutter seems to have been cured and the performance of the car is more consistently strong, with no sign of smoke - so the tip-off that this fault was affecting the EGR valve and other emissions equipment seems to have turned out to be spot on. Thanks to all for the suggestions.

Idle is occasionally still very slightly lumpy, but we really are talking a barely perceptible vibration every now and again, which I can live with for the time being.

05 2.0HDi Lumpy Idle, Stutter and a few other bits - Angela165

Hi, thought I would add my tuppence worth. Just found this thread after googling defect in brake vacuum pump C5. Just got a recall notice through for my C5 re this. Annoyed that it has taken so long for this to come through to me when the problem has obviously been ongoing for a number of years. My C5 tourer 2.0 (2008) started to give me problems a year ago - got the fright of my life when the brake pedal appeared to fail (hard as a rock) just metres from my front door - overshot a giveway but due to my travelling so slow wasn't a major problem but a car had to swerve around me. Immediately took it to citroen garage and they kept it for two days - as far as they were concerned nothing wrong with the brakes - claimed I must have hit a bit of black ice - basically did not believe my description. It has continued since, most mornings, especially if a cold morning but once I've deliberately pumped the brakes several times it sorts itself out. Didn't go back to garage as I felt they wouldn't believe me!!!!

Will be glad to get this sorted at last via the recall but very annoyed the garage didn't pick this up last year when I complained!

 

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