rear suspension sinks (C5)

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Post by myglaren »

The only one anything like close to you is in the Glasgow area.
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Post by ed1 »

Jeepers creepers - this forum is incredible!
Many thanks!
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Post by BX »

C5s which sink? If they sink the problem is almost always one of the rear suspension units. disconnect the leakback pipes at the rear (plastic/rubber pipes from the gaiters on the rear suspension unit) and see which side drips. If citroen dosn't cover you on it fit a second hand one. Usually if these units are going to fail they usually do it early in life.
Lexia will not tell you anything re the fault.
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Post by viorelovidiu »

BX wrote:C5s which sink? If they sink the problem is almost always one of the rear suspension units. disconnect the leakback pipes at the rear (plastic/rubber pipes from the gaiters on the rear suspension unit) and see which side drips. If citroen dosn't cover you on it fit a second hand one. Usually if these units are going to fail they usually do it early in life.
Lexia will not tell you anything re the fault.
if left rear suspension unit will leak from leakback pipe and the car sinks, right rear suspension unit will not leak because could not keep the car up by itself? how we can be sure who is the defective suspension unit?
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Post by BX »

The one which drips is faulty. Undo & pull back the gaiter and you can see the fluid exit the cylinder if you really want to be sure
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Post by ed1 »

Thanks for these extra bits of info guys! Will check the gaiters today.
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Post by DHallworth »

I was in this car last night when we had it on the Lexia.

It's a strange feeling....

You don't feel it sinking at all, then all of a sudden you hear a whirring noise and can feel it lifting the back of the car back up.

It must have done it at least half a dozen times whilst it was plugged in last night.

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Post by ed1 »

Thanks again David for checking with the lexia! Info gathered:-

Suspension ECU:
Permanent Fault - No Communication with steering wheel sensor

Temporary Fault - No communication with the built in systems interface no signal

ABS ECU:
Steering wheel angle sensor coherence.
The ABS ecu couldn't be cleared for some reason - possibly sensor completely knacked? However, the display showed the angle to be changing when turning the steering wheel?

Any further advice offered will be very much appreciated.

Eddie

Incidentally - anybody reading this in / around the Glasgow area - David is very helpful and worth getting to know! A lexia inspection and needed to be persuaded to accept something for a couple of pints!! Blooming better service than you get at dealerships! Impressive C6!
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Post by cachaciero »

ed1 wrote:Thanks again David for checking with the lexia! Info gathered:-

Suspension ECU:
Permanent Fault - No Communication with steering wheel sensor

Temporary Fault - No communication with the built in systems interface no signal

ABS ECU:
Steering wheel angle sensor coherence.
The ABS ecu couldn't be cleared for some reason - possibly sensor completely knacked? However, the display showed the angle to be changing when turning the steering wheel?

Any further advice offered will be very much appreciated.

Eddie

Incidentally - anybody reading this in / around the Glasgow area - David is very helpful and worth getting to know! A lexia inspection and needed to be persuaded to accept something for a couple of pints!! Blooming better service than you get at dealerships! Impressive C6!
I'm surprised that you could clear the suspension fault, if there is no comms with the wheel sensor, this would be a permanent fault which I would have expected to come back almost as soon as it was cleared.

The ABS ECU works as I would expect in that there is a permanent fault and until the source of the fault has been rectified the ECU will not clear.

I am assuming that this a C5 II the steering wheel sensor the suspension ECU and the ABS/ESP ECU all get their data from a common CAN bus which also talks to the BSI. Any disconnection of the data bus to any ECU would result in much more than one item of data loss, the steering wheel sensor produces as I understand it two data messages one being steering angle the other being angular velocity. I don't know if the Suspension ECU and the ESP ECU use both bits of data, they do both use at least some of the data.
It may be that it is the rate part of the sensor which is not working which would explain why you can see wheel angle changing and might explain the somewhat cryptic coherence message.

Any way you need to do more investigation on the steering wheel sensor ECU Basic check is it getting power assuming the answer to that is yes then. ideally you need to be able to examine the data lines going to the unit with an oscilloscope and to do this you need a break out cable although you could probably get away with dressmakers pins pushed through the wire insulation and the scope probes hung onto the pins. I suspect that a new steering wheel sensor /ECU will be very expensive which is why you would want to be absolutely sure it really was u/s before changing it.

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Post by ed1 »

Ok guys.
Still haven't got to the bottom of this yet but have had the dealership agree to refund my inspection fee - don't think he liked me saying I had no confidence in his diagnosis.
Anyway, weird thing - at the weekend (very warm) I noticed the car was taking longer to sink on Saturday night but was sunk on Sunday morning. After that - no sinking on Monday, Tuesday and Wednesday. It had sunk by this morning though, overnight. What has incredibly warm weather got to do with the rear not sinking - link between temp. and pressure in system or link between temp and expansion of wires / connection in electrical bits????
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Post by viorelovidiu »

that`s happened to me a lot! no explanation for this behavior, sorry. seems to keep up the car for three days and the sinkin starts again... I described this behaviour in a thread started by me here. maybe a problem with the pump? those tiny holes there are not perfectly sealed by valves letting fluide LDS to sink back to reservoir?

very confusing though, anyway next month i`ll try to replace LDS - maybe some infiltration/impurities could cause such a behaviour.


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Post by dnsey »

Given the emphasis Citroen place on almost sterile cleanliness when working on LDS-based systems, I suspect that there are some very narrow oilways etc which are easily blocked by small particles.
I don't know if there's an LDS version of Hydroflush available, but if so, it might be worth a try.
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