Xantia V6 broken exhaust (update: and rough low rpm running)

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Thanks Jim, but I'm afraid with the money I've already spent on the car if it does go belly up I'll have call it a lesson learnt and break it. :( My other half would not be amused at me trying to take the gearbox out, (I'm on thin ice already with this car due to the amount of time and money I've spent on it, she just wants a car that works and doesn't really care what it is) let alone the fact that I have nowhere and no way of doing such a thing.

The other noise sounds like a very noisy dry bearing or a bearing turning in its housing. I know autos sometimes do make a bit of noise that sounds like a bearing turning in its housing (my previous auto did at low RPM in 3rd) but it was rather loud and came and went with load as the box tried to decide what the heck it was doing. It was shuddering badly on takeoff below 15mph as well a few times although that could still potentially be plug leads. I'm still going to fit the new plug leads when they arrive, I don't have much choice.

It's not a happy bunny indeed. What I don't understand is why its so intermittent, its almost schizophrenic. When I took lexi for a drive only a week ago it would barely play up and it was almost flawless on the way home that night after doing the plugs and the manifold gasket.

If I had to guess (with my limited understanding of autos) I would say there is some problem with the main rail pressure regulation that is on a bad day allowing the pressure to drop causing either slipping of the main clutches/brakes, or difficulty in regulating the torque converter lockup clutch, or both.

It seems almost as if the ECU is constantly trying to adapt too, if I do a reset, once it has adapted (which doesn't take long) it usually works a lot better for a few days then deteriorates... perhaps the ECU adapts to the behaviour of the gearbox with a certain rail pressure, and when the pressure increases or drops from what it has learnt it fails to regulate the clutches properly...in particular the partial slip mode of the torque converter lockup clutch must require a very delicate balancing act from the ECU, and probably requires well regulated supply pressure to work reliably.

Whether the pressure is varying because the filter is blocked starving the pump, a faulty electrovalve, bad wiring to the ECU, a fault in the valve block, is anyones guess. One minor consolation may be that if the gearbox behaves more or less normally SOMETIMES, the clutches may still be ok, although too much driving with them slipping will see that situation change for the worse no doubt...there was no evidence that I could see of clutch debris in the oil I removed. (Although whether the filter would trap that and prevent it being drained I don't know without studying the circulation paths)

Time for me to break out the training manual again and read up on how the valve block, electrovalves and pressure regulation works...
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CitroJim
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

Simon, I'm really sorry but I think it's time to buy a wreath for your gearbox :cry: :cry: :cry:

The noise you hear is possibly indicative of the torque converter neck bearing welding itself to the neck and spinning in the oil pump housing...

Here's one that was wrecked earlier:

Image

The cause is ,I believe, the lockup clutch breaking up and shedding friction material into the oil which chokes the filter and causes a dangerous reduction in oil pressure. The neck bearing is the first to go followed by the output shaft bearing which causes some interesting carnage. What you see here is the remains of a taper roller bearing :shock:

Image

If you stop driving now the damage will be minor and you'll escape with just needing a TC rebuild, a new oil pump (maybe), filter and gasket set.

If you drive to the bitter end it'll only get worse and get more expensive to repair. It may well strand you too...

Cost is going to be significant in any case. I'd be tempted to buy one of the several thousand V6s currently on ebay, at least as a stand-in whilst you get yours sorted. My website shows how to do the rebuild. A nice winter project :wink:

Simon, I'm sorry to give you this news :(

There is a possibility that the neck bearing has already welded and the output shaft bearing is rapidly going which may well be partially seizing the 'box and might account for the running problems.

Certainly under low oil pressure the auto-adaptives will be going loopy trying to keep up with what's going on now.
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Very sobering thoughts there Jim, I'm afraid you're probably right :( I've already paid for the spark plug leads and oil for a second ATF change so I might as well go ahead and do those, you never know. As I said, only a week ago it was running relatively ok, whatever is happening seems to be intermittent. I would have thought a seizing bearing would be permanent not intermittent but who knows.

As it happens, I interviewed for a new job today and found out tonight that I've got it :) which means my daily commute will change from car to train in a couple of weeks...(although it was only 2 miles a day anyway) which means I will be able to keep the driving down to an absolute minimum (fortnightly supermarket runs) while I ponder what to do about the situation... :?
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Just thinking about this a bit more Jim, does the neck bearing support the input (engine) side of the torque converter, or is it the support between the torque converter and the rest of the gearbox ? (eg the output of the torque converter) I've been looking at the diagrams but can't quite make up my mind where it is.... is it some sort of bronze bush, or does your photo just show whats left of a ball or needle race ?

If the bearing is as far gone as your picture above would you expect to hear any noise from it while idling ? Tonight I was trying a little test - engine idling and handbrake on, going between reverse, neutral and drive.

In drive or reverse the output speed of the torque converter will be zero RPM while in neutral it will be close to engine RPM. I heard absolutely NO difference in noise between neutral and drive/reverse. In fact there is no audible noise from the gearbox in any of those three modes, and I listened very carefully. (I have a poor nose, but good ears :lol: )

If the suspect bearing is on the output side of the torque converter I would have thought I'd hear at least a small faulty bearing noise in neutral, but I heard nothing. Of course if the bearing is on the input side my test would mean nothing...
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Hell Razor5543 »

Congrats on the job front.
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Hell Razor5543 wrote:Congrats on the job front.
Thanks. :) Better wage, 8:30 to 4pm Monday to Friday in the IT dept of a College instead of rotating shifts (including evenings and weekends) in a call centre. Result! :-D
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

More thoughts Jim, this time about the torque converter lock up clutch. From page 164 of the training manual:
If the lock-up operating law specifies that it must be in the controlled state, it is up to the ECU to work out the most suitable value of slip.
This value is defined by a difference between the engine speed and the turbine speed (N input to transmission). The value of this difference is given in a cartographic map f (α/idle speed, Nmot).
After operating the proportional electrovalve designed for this purpose, the ECU checks that the actual engine speed is indeed the same as the speed from the cartographic map which is therefore the desired speed.
The controlled state is particularly delicate and complex to manage in the following cases: (my emphasis)
• During variations caused by the engine speed; the desired slip, in other words the difference between the engine speed and the turbine speed, is determined and managed in an open loop using a specific strategy.
• If the vehicle switches from the "pulling" state to the "decelerating" state, the ECU must invert the sign of the value of the difference in engine speed (ΔN = turbine speed - engine speed and not the inverse).
Physically, the operation is difficult to perform; so that transmission occurs correctly, the pressure exerted on the lock-up is set to zero for a fraction of a second.
In other words, under conditions of constant RPM and torque closed loop feedback is used to regulate the slip in the piloted/controlled slip mode - as described elsewhere in the manual the ECU measures the input and output speed of the torque converter, and makes small adjustments the oil pressure to the clutch.

However when there is a sudden change in RPM closed loop feedback can no longer be used and the ECU reverts to an open loop strategy to approximately regulate the slip. Furthermore if the car goes between power and overrun or vica versa (sign change, above) it momentarily unlocks the clutch completely before reapplying it.

What I'm thinking here is that if the torque from the engine is very erratic at low RPM under load due to for example misfiring, the constant variations in torque may be confusing the ECU (making it think there are sign changes in the torque) causing it to keep releasing the the clutch multiple times a second - in other words an oscillation. It could well be the shudder or groaning effect, and if its due to the above it might be the rough running of the engine causing it... so there is still some hope that at least some of the symptoms may be due to the engines inability to provide sufficient and smooth enough torque at low RPM...

Another interesting section on page 159:
A - AUTOADAPTIVITY TO ENGINE TORQUE
The ECU alters the maximum value of line pressure depending on the turbine torque to be transmitted.
It therefore adjusts the line pressure: • between 15.5 and 18 bar in 1st and reverse gears, • between 5.5 and 8.8 bar in the other gears.
The ECU imposes a line pressure of 15.5 - 18 bar in the following cases if: • a gear is being changed,
• downgraded mode is operational (transmission is locked in 3rd hydraulic)
In stabilised mode, the ECU can switch the pressure from one value to another depending on the turbine torque:
• 5.5 - 8.8 bar for turbine torque ≤ 230 mN, • 15.5 - 18 bar for turbine torque > 230 mN.
In other words the line pressure is regulated not just based on what gear you're in, but the instantaneous torque being supplied by the engine, which is calculated by the engine ECU and sent to the gearbox...it occurs to me if the engine is running erratically under low RPM load the calculated torque figure that is being sent to the gearbox could be fluctuating all over the place confusing the gearbox. Lots of good stuff in the manual, I need to do more reading :)

I haven't quite given it up for dead yet, I'm definitely going to do the spark plug leads and check the connectors between the ECU and the gearbox for corrosion.
andmcit
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by andmcit »

At least the job improvement is good news Simon - sad to hear your v6 'box
isn't joining in with the positive vibes. I'd seriously take into consideration that
Jim fella's offer of rebuilding the innards mind! Would finances allow that other
Glasgow v6 with 90k miles on Gumtree to stand in for active duty whilst the silver
car has time to recover?

Image
http://www.gumtree.com/p/cars-vans-moto ... /112863139" onclick="window.open(this.href);return false;
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by xantia_v6 »

Mandrake wrote:Just thinking about this a bit more Jim, does the neck bearing support the input (engine) side of the torque converter, or is it the support between the torque converter and the rest of the gearbox ? (eg the output of the torque converter) I've been looking at the diagrams but can't quite make up my mind where it is.... is it some sort of bronze bush, or does your photo just show whats left of a ball or needle race ?

If the bearing is as far gone as your picture above would you expect to hear any noise from it while idling ? Tonight I was trying a little test - engine idling and handbrake on, going between reverse, neutral and drive.

In drive or reverse the output speed of the torque converter will be zero RPM while in neutral it will be close to engine RPM. I heard absolutely NO difference in noise between neutral and drive/reverse. In fact there is no audible noise from the gearbox in any of those three modes, and I listened very carefully. (I have a poor nose, but good ears :lol: )

If the suspect bearing is on the output side of the torque converter I would have thought I'd hear at least a small faulty bearing noise in neutral, but I heard nothing. Of course if the bearing is on the input side my test would mean nothing...
The bearing supports the transmission end of the torque converter casing, which always runs at engine speed, and which drives the transmission oil pump.
It is a white metal type of bearing (it is pressure lubricated).

Sorry to hear of your predicament.
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Thanks guys, not really sure what to do.

Even though it looks in good condition I'm not sure that I want to buy another automatic and end up in the same predicament in a few months or a years time. (Not to mention another low MPG car) A lot of the work that I've already done to this one might have to be re done, including tyres, spheres, handbrake cables, droplinks etc.

Also I can't afford to insure two cars at once which would mean putting the old car off the road by transferring insurance, and then do what with it ? I couldn't in good conscious sell it when it has obvious problems driving and is likely to die in a few months. All I could do is either sell it to someone willing to take it on as a project who will get the gearbox done, or break it for parts. I don't have the space or money to keep two cars for any length of time.

None of the alternatives appeal much. :?
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CitroJim
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

Oh yes, very important to eliminate everything else before finally reading the last rites to the gearbox. Those noises worry me though Simon. I wish I could put my ear to them.

That's not a bad Idea of Andrew's - buy that green one to tide you over...
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

The misfire seems to have got quite a bit worse in the last week, when starting the car late at night to come home from a back shift (in cold damp conditions) I can hear the obvious uneven beat of a misfire as the revs drop from 1500 to 900 or so during the initial startup. Either my disturbing the rear plug leads (completely removing them, bending and twisting them around checking their intermittent fault etc) has made the plug leads even worse, or there's something not right with the plugs themselves...

Is it possible I haven't got the plugs seated/sealing properly ? I'm a bit of a chicken when it comes to torquing spark plugs, ever since owning a GS that had soft alloy heads that were oh so easy to strip. What is the recommended way to torque the spark plugs in the V6 without access to a torque wrench ?

I assume you tighten them hand tight first until they bite then turn them a certain number of degrees with the socket wrench ? They seem to pull up tight fairly quickly but I'm a bit chicken to tighten them too much.

As I mentioned earlier the spark plug seats in the head aren't exactly spotless, there's a bit of muck on some of them I can't seem to clean away, so I'm wondering if there is a wee bit of grit under the spark plug washer preventing a good seal and good torquing.

Any suggestions anyone on the best way to clean the cylinder head tops down inside the tube, and how much to torque the spark plugs ? (And is it ok to remove them for inspection then re-torque or will the crush washer not bite as well a second time ?)

Sorry for the really basic questions :oops: but in all the years I've worked on cars I've had very little cause to change spark plugs, and never on an engine where access to them was down a long skinny tube... :?
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Hurrah, my new spark plug leads have arrived :)

A quick check with an ohm meter and they measure between 4.8k and 6k depending on the length of the lead, and as expected I can easily get a good connection that measures ok regardless of twisting the leads around. Unlike the coil pack I got before, the new leads include the push on rubber spark plug connectors, all they're missing is the curved plastic guide that bolts onto the corner of the inlet manifold, so I'll need to transfer the old one over.

Is there any identity as to which spark plug leads go where on the coil pack ? So long as the curved plastic guide is attached to the leads its obvious which lead is which, but I'll have to be careful to take note of the order of the leads in the guide when I transfer the guide over to the new cables...

Will be interesting to see what difference it makes, now all I need is a dry day off work. (In other words NOT today... :roll: )
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Xantidote »

Fingers crossed that the new leads give you some improvement, Simon
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Thanks. Picked up an inlet manifold gasket today too so I'm all set to do the plug leads, all I need now is a sunny day off work....so sometime next year then :lol:

After all the apparent slipping that the gearbox has been doing lately I thought I'd put the Lexia on and see if there were any faults logged regarding clutch slipping, nope, no faults logged at all. :? (so much for diagnosis by fault code, I think it will finally log a fault AFTER the gearbox dies :roll: )

Decided to reset the auto-adaptives again, (what do I have to loose) went for a 10 minute drive consisting of lurchy gear changes as it adapted itself and afterwards although its still groaning a bit under load at low RPM it no longer seems to be slipping under applied power when accelerating like it has been over the last week. Hmmmmmm.....a progressive change in gearbox characteristics after the oil change perhaps ?