C5 HP20 causing grief

[mongoose100]

Not sure whether to panic here but the C5 has started violently surging at light to medium throttle - feels to me like the torque converter is locking and releasing constantly

Coming down a hill holding second gear at mid revs I notice fluctuation of about 500rpm - not nice

My question here is; is the box likely to be salvageable and will a fluid change possibly fix it?

Jim HELP !!!

[CitroJim]

Hi Regan,

Ummm, that's an interesting one. My first thought is that it's the engine causung the problem but the 500 rpm difference possibly might suggest the torque converter is locking and then unlocking - There is a very remote chance that the lock-up clutch is badly worn. The problem is determining if it's the engine or the gearbox.

Berfore doing any of what follows, does this effect only occur on trailing throttle? does it immediately clear as soon as you put your foot down and the engine is delivering power? If it does then the engine is the very most likely culprit. I'd say that the engine ECU is not aware the throttle is closed and is therefore mis-fuelling or not properly effecting fuel cut-off on the over-run. The throttle pot may be bad or the ECU needs recalibrating to understand when the throttle is closed. Theer is a procedre to do this that does not need a Lexia. I'd be checking all this first before diving into the gearbox.

First gearbox test is to drive in snow mode. Lockup is not so readily applied then.

The other test you might try is a drive with the 'box forced into limp home (3rd gear emergency) mode. This can fairly easily be gained by disconnecting the KOSTAL plug on top of the gearbox. or alternatively, with battery disconnected, disconnecting the autobox ECU. I'd prefer a disconnect of the KOSTAL connector myself.

Be aware that on selection of drive or reverse in limp mode there will be a fair old clunk. However, the point of this test is that the torque converter will not lock up, only one gear will be selected and the gearbox will become a constant to try to eliminate if it's engine or gearbox causing it.

Ideally, a Lexia looking at live paramaters from the gearbox whilst driving would be good. You could then see at a glance if the torque converter is slipping by looking at engine RPM and gearbox input speed although if there is ever a serious descrepancy the gearbox ECU should log a fault.

As I say, clear the engine from enquiries first.

[mongoose100]

Was hoping you'd come along Jim!

Seems to only do it on trailing and light to mid throttle. When planting it, it very quickly locks the converter and pulls well.

I'm not convinced that the engine is developing full power tho, since owning it, my v6 Xant has always comfortably had the upper hand - 20 less HP in the old motor too.

Will try your tests tomorrow.

All my experiances with the HP20's dying is the familiar buzzing followed by loss of drive - this one is deathly quiet

[CitroJim]

All my experiances with the HP20's dying is the familiar buzzing followed by loss of drive - this one is deathly quiet

Indeed, they're pretty much symptomless right up util the end usually. It's invariably a death-buzz or a death-howl

If you have the VVT engine then that could be playing silly sods. Imagine if it was switching back and forth then that might cause it as well as making the engine feel a bit flat.

Definitely concentrate on the engine!!!

[mongoose100]

Would the cam timing affect it on trailing throttle? The jerks are rather sharp - feels similar to fuel surge in the way of sharpness

[CitroJim]

Would the cam timing affect it on trailing throttle? The jerks are rather sharp - feels similar to fuel surge in the way of sharpness

I've no idea Regan as I have nil experience of the VVT but knowing what it dfoes, I'd think so...

Wonder if you can disable it for a test?

[mongoose100]

It only looks like a solinoid on each of the inlet cams, tempted to disconnect it and see what happens... Cant see valves crashing into pistons?

[addo]

It'll just sound really rattly, most likely - especially when cold.

[mongoose100]

Confirmed. Transmission dead. Was greeted with bang, clunk and the death buzz!!!

Now, rebuild or second hand?

[xantia_v6]

Knowing what we do about these transmissions, it is almost certainly best to rebuild it. Do you have facilities to do it yourself? I would imagine that you can find someone in NZ to rebuild it for you, more reasonably than here in the UK. You might want to directly source the parts form the UK...

How many km did it manage?

[addo]

Nice work. I'd be tempted to use a UK rebuild service (hint, hint!) as they will have likely dealt with far more than an NZ firm.

At the very least I'd buy a UK rebuilt converter and source the kit overseas.

[CitroJim]

Regan, sorry to hear this

Nice work. I'd be tempted to use a UK rebuild service (hint, hint!) as they will have likely dealt with far more than an NZ firm.

At the very least I'd buy a UK rebuilt converter and source the kit overseas.

Mackie transmissions do a rebuild service and a torque converter service. The rebuild will be strong money though. Circa GBP 2000 plus shipping...

Are you able to have a go yourself Regan?

[mongoose100]

At this stage, I'm gonna be having a legal battle with the car shark who sold it - his mechanic replaced the 'solonoids' in the box just before I purchaced it 10,000Km ago.

I'm guessing he means the electrovalves?

Jim, does the valve block need to be removed for this? Also, how much oil would be lost in this process? Reason I'm asking is that I've dropped a oil sample and its RED! Guessing I'm a victim of the dreaded D3!?

Is someone able to email me a photo of a glass of new and possibly old (10,000Km) of the LT 71141?

10K and 5 months of C5 ownership and then this! Not bloody cool!


The other thing... Although I doubt this will work - would flushing the D3 out and replacing with LT 71141 fix this, or is the damage well and truly happened?

[addo]

It's ph*cked. No fluid change will fix the physical damage that has occurred - which BTW is unlikely to be a solenoid issue. Incorrect oil may have hastened the failure however you are probably right on the statistical point where it will occur anyhow, regardless of who sold the car to you. Wrong oil level would also potentially cause damage.

Oil type diagnosis is confused by the Nulon full synthetic ATF which is red but smells like LT71141.

[mongoose100]

It's ph*cked. No fluid change will fix the physical damage that has occurred - which BTW is unlikely to be a solenoid issue. Incorrect oil may have hastened the failure however you are probably right on the statistical point where it will occur anyhow, regardless of who sold the car to you. Wrong oil level would also potentially cause damage.

Oil type diagnosis is confused by the Nulon full synthetic ATF which is red but smells like LT71141.

Adam, I'm trying to work out if the box needed to be drained to do these solenoids... The fluid smells like old D3