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

[Mandrake]

Just drove the 20 mile round trip to Glasgow and back, most of it 60/70mph on the M8, some in 30/40mph zones, and not the slighest hint of a groan or shudder from the gearbox despite trying to provoke it at slow speeds in high gears, and generally good behaviour from the gearbox overall in terms of shifting etc, it seems to have further improved since the day I did the oil changes. So the oil changes were definitely not placebo in effect, and there might be hope for this gearbox yet.

One symptom that I thought might be the gearbox is still there, but I'm now thinking maybe it isn't the gearbox. If I'm doing say 50mph and I put my foot down a little bit the revs will rise like there is a bit of slip in the torque converter lockup, then they will drop back again. EG a small surge in RPM that drops again. If I applied a moderate throttle the lockup clutch is opening letting the RPM rise about 600rpm or so for the same speed, sounding a bit like a down change, but its definitely still in 4th.

My original theory was that the lockup clutch was struggling to lock properly under load, with a little bit of slip to begin with and then letting go completely with heavier throttle, but tonight I tried engaging snow mode, in this mode the small initial rise and drop in rpm is still there as you apply some throttle, but I can then apply a lot more throttle without triggering a kickdown and without the lockup clutch slipping at all - it holds steady and the car accelerates normally. So this suggests to me that the lockup clutch IS able to lock properly and pass the required torque without slipping when commanded to do so by the ECU.

I now suspect the small surge in rpm could actually be the engine putting out a little surge of torque that drops away again when you press the throttle, in other words related to the lack of engine power issue.

Engine power was down quite a bit tonight, I have to admit I am leaning towards the blocked exhaust theory, it does feel a bit like the engine is choked and unable to breathe properly until the revs climb up a bit. Whether its the cat or whether it could be a disintegrated centre silencer or back box is unknown.

It could still be a sensor fault causing lack of fuelling or the timing to be retarded, (since it does seem intermittent not permanent) a new MAP sensor is cheap and easy to fit even in winter so I'm going to do that first, and probably the coolant sensor as well, if no improvement I'll have to get someone to look at the exhaust system in a couple of months....it does seem that for the time being the gearbox is largely behaving itself and I'm just looking at an engine performance problem. I seem to be making some progress bit by bit.

[Mandrake]

Finally got around to comparing samples of oil from each oil change in test tube size bottles - in large bottles I couldn't tell any difference but the difference in opacity of the oil is pretty obvious now. The tubes from left to right are the oil that was drained in each of the four oil changes, while the 5th tube on the right is brand new oil for reference:

It's hard to appreciate the difference in photos, but the oil from the first change is completely and utterly black and opaque, even in that small size tube - I can hold it up to a light and see nothing at all through it.

The second change you can see a little bit of light through it but not much. By the 3rd its starting to look like oil and the 4th change whilst not as clear as the new oil is a long way towards being clean. (Bearing in mind that the new mixture of oil now in the gearbox will be 50% cleaner again than what was last drained out...)

So much for sealed for life, 100k and the oil looks like this...

[Hell Razor5543]

Did you offer number 1 to the local council traffic section for use as tar? It looks like it might be a suitable alternative.

James

[CitroJim]

Simon, your row of specimens is very interesting indeed

Number 4 is about what it looks like after 15K in a rebuilt 'box.

I really need to swap the oil in my V6 (both engine and 'box) and when I do I'll keep a sample to compare against yours. I reckon mine's dome around 20K now since the last change.

It'll be interesting to compare.

Did you offer number 1 to the local council traffic section for use as tar? It looks like it might be a suitable alternative.

James

I reckon it might be a good cat repellent. Or perhaps on seconds thoughts, knowing how it smell it might attract them

[CitroJim]

Simon, thought you'd like to see my specimen...

This I reckon is about 20-25K old. It looked crystal clear as it was draining but as you can see it's not 100% clear in the eggcup - somewhere between your 3 and 4 I reckon...



I saved a load of time changing the oil. I measured the old stuff that came out (4.3 l) and measured the same back in... Using that method makes it a very easy job indeed

[Mandrake]

Simon, thought you'd like to see my specimen...

This I reckon is about 20-25K old. It looked crystal clear as it was draining but as you can see it's not 100% clear in the eggcup - somewhere between your 3 and 4 I reckon...

Yes mine looked fairly clear while draining too, at least the last two times, but it can be deceptive since the apparent clearness of the oil depends on both the diameter of oil the light is passing through, and the lighting conditions. (As well as the camera exposure in photos)

Trying to compare yours to mine in different size containers and different lighting conditions with different camera exposures won't really give any meaningful comparison, the best bet is to compare it to some brand new oil in the same size of container so there is a frame of reference in the same lighting conditions.

I saved a load of time changing the oil. I measured the old stuff that came out (4.3 l) and measured the same back in... Using that method makes it a very easy job indeed

How are you managing to get 4.3 litres out ? I'm getting almost exactly 4 litres out each time with the front of the car up on ramps...I pour about 3.5 litres in straight away without checking the dipstick, then add the rest in 200ml amounts checking the dipstick in between.

Because my ground is not perfectly level I take two measurements, one with the car one way around, one with it facing the opposite way, and take the average of the two dipstick readings. (One is at the top mark with the car one way around, the other at the bottom mark, both are in the acceptable range and average to half way between the marks so I should be ok)

Do you think 20,000 miles is a good conservative changing interval to keep the oil and gearbox in best condition ? Pity that Citroen went for "sealed for life", with a 20,000 interval my box would have had 5 changes by the time I got it, if previous owners had kept up the maintenance. I'm willing to bet that it would have made a large difference to the longevity and smooth running of the box... It's hard not to think of no recommended oil changes being nothing short of planned obsolescence...

[Mandrake]

Did you offer number 1 to the local council traffic section for use as tar? It looks like it might be a suitable alternative.

Nope, funnily enough the consistency is nothing like tar, its just as runny as new oil, in fact if anything its more runny and water like...

[CitroJim]

I think 20,000 miles is a good one Simon and what I try to practice...

Point taken on the oil sample. I'll get another eggcup and fill it with new oil...

I drained mine on high and on level ground, no axle stands or jacks used. Just popped the car up on high with a shallow catch container underneath (my trusty giant cat litter tray) and drained. Measured the old stuff using a litre plastic IKEA measuring jug I keep specially for the purpose...

I wonder about the calibration of it because 4.3 litres on that was not quite 2 of the 2 litre bottles of the genuine Citroen stuff so let's agree on 4 litres!!!

[Mandrake]

If I do any more changes I think I'll just do it on high then without the ramps, to save extra complication.

Just looking at my samples again today and I've noticed something after they've sat for a while, samples 1 to 3 all have a little bit of white foam/froth at the bottom which I'm assuming is water ?? Sample 4 has no trace of the white foam. When turning the bottles upside down the white foam sinks...

(Higher res image this time to make it easier to see the small bubbles, click to expand)

Playing devils advocate here, but could this be a sign that there is a small amount of leakage of coolant into the gearbox oil due to a hole in the heat exchanger ? A possible reason why sample 4 has none visible is that changes 3 and 4 were done on the same day with about 20 miles driving in between them, while all the earlier changes were separated by several weeks of normal driving. (Also I've been running with the pressure cap loose for the last few weeks which might reduce any leakage in the heat exchanger if there was a hole, since the cooling system isn't pressurised now)

If that really is a bit of coolant getting into the oil could that explain the groaning noise I was getting ? Could it be the real cause of the problem rather than metallic particles or just plain dirty oil ? I wouldn't imagine that water being mixed in with the oil would make the clutches very happy...water is NOT a good lubricant and might cause grabbiness in the clutches due to upsetting their delicate friction curve characteristics.

Since the oil can reach 105 degrees during long periods of fast driving, thus boiling it to steam, and potentially liberating it through the air breather, it seems likely that it would accumulate with lots of around town driving where the oil only gets to around 80-90 degrees, which is exactly what the car has had over the period where it started to misbehave.

What do you think Jim ? Have you heard of any HP20's that have died due to a holed heat exchanger ? What might the symptoms of water in the oil look like ?

Before I worry too much, the bottles that I stored the old oil in prior to sampling were just pepsi bottles that had been rinsed clean, and I didn't make any particular effort to make sure they were completely dry before using them, so it's possible that some of them could have had a few dribbles of water in them... but I think its something to keep in mind, and if I do another change I will make sure the containers are spotlessly dry to see if there is any further sign of froth or foam.

Edit: one more thought I've had is that changes 1-3 were all done at an oil temperature of 80 degrees, while change number 4 had been after a second test drive by which time the oil had reached 105 degrees, so any water in the oil would have evaporated during the draining process, thus leaving no evidence in the sample...

[CitroJim]

I don't think you need worry about a holed heat exchanger Simon as the pressure in the cooler is far above that in the cooling system and I'd expect to see LT in the coolant before seeing coolant in the LT. I've known coolers block on the coolant side but never on the oil side or for them to leak.

However, having said that - if coolant had got in the 'box it would be toast by now as ethylene glycol and friction material don't mix at all well. It is said that just a tiny amount in the oil will strip the friction linings in no time at all and cause huge damage.

I noticed with my specimen that it was full of air bubbles for ages after I caught it in a jar. It did settle and I'll have a look later to see if there's any foamy bits on top of it. Can't say I've noticed though...

I'm inclined to think it's likely just condensation from short runs and cold weather and very possibly too some moisture in your coke bottles.

Simple way to find out... Heat a sample to drive off any moisture and see if it remains...

It may be just an artefact of the anti-foaming agents in the oil deteriorating - they work very hard in a gearbox...

If you are really worried I wonder if you could send a sample off to a lab for full analysis...

[addo]

It's not antifreeze. That retains colour enough to be readily identified.

[Mandrake]

Thanks Jim,

I was just exploring all possibilities, but you've reassured me that its probably just normal condensation, I'm assuming that the air breather near the dipstick means that it's not a fully sealed system, therefore moisture from humid air would eventually work its way into the air space in the gearbox and then condense in cold temperatures. Long drives that got the oil over 100 degrees would then drive the moisture out of the oil again, as the oil drained at 105 degrees shows. (I did actually see a vapour rising from the oil in the collection tray, although ambient conditions were very cold at the time)

I'll keep an eye on it if I do any further changes, but it looks like it's nothing to worry about.

[CitroJim]

That's right Simon, it's not a sealed system and will certainly pull in moist air under the right (wrong) atmospheric conditions...

[Mandrake]

Simon, if you know where to look, a MAP sensor is quite cheap.

This is a '9H' just a bit dearer from the 'bay

Just ordered this MAP sensor, should have it by the weekend. I have a gut feeling that this could be a significant chunk of my intermittent poor engine power and responsiveness, so we shall see.

The brand is Erste Wahle, is this a good/bad brand ? Are there MAP sensors, and then MAP sensors, or are most of them pretty decent ?

I noticed last night while waiting to pick up the other half with the engine sitting on about 60 degrees that whilst the idle was steady, if I depressed the accelerator even a tiny amount, (to take the ECU out of "idle" state) and held it steady there, the revs were going up and down like a yo-yo about once a second, dropping to the point of staggering and almost stalling, zooming up to about 800, dropping again etc indefinitely. I think this is consistent with a dodgy MAP sensor ? This behavior I've seen before but it seems much worse than previously. As soon as I release the throttle it goes back to a steady idle at the correct speed. I don't think there's any problem with the idle stepper motor as it compensates correctly for aircon being turned on and lifts the idle when turning the steering.

Other things it sometimes does is as you press the accelerator not only do the revs drop a bit at first, it takes a significant amount of throttle before the revs will increase above idling, at which point it will then shoot up to about 1400rpm or so - there is no way to adjust the throttle to get a steady speed between idle and 1400rpm. (when stationary in neutral) Also consistent with a MAP sensor ? Yet more clues, sometimes when coasting and then gently accelerating there is a momentary hesitation / flat spot.

In other news, I think the gauge temperature sender might be faulty - I've noticed this before on my Scotland tour a few months ago, sometimes while the engine is fully warmed up the temperature gauge will drop from 85 or so down to 60 in the period of a second or so, and intermittently go back to the correct reading. The other day it was doing a similar thing where the reading was dropping down to about 60 degrees when fully warmed up driving on the motorway, and the funny thing was that I seemed to be able to modulate it by pressing the throttle! The gauge would go up and down between 60 and 85 as I pressed and released the throttle, at least for a few minutes, then it came right again. (Engine torque flexing the wiring loom maybe ??)

I don't think its likely to be an air lock as I haven't touched the coolant system apart from topping it up, its never shown any signs of overheating or boiling, so I do think its a sensor or wiring problem. Where should I start looking ? I know where the ECU coolant temperature sensor is, but I'm not sure where the gauge sender is...

[Mandrake]

Aha, I'm paid !!

While I'm waiting for the MAP sensor to arrive, I was browsing back through the thread and realized that another thing you guys suggested needs checking is the fuel filter, somehow I've overlooked that this whole time. I would feel like a right numpty if the loss of power was partly a blocked fuel filter causing fuel starvation. So where is it on the V6 ? In the engine bay, or near the fuel tank ? Any suggestions on make/brand of replacement and how many ££ I would be looking at ?

I'll also get a coolant temperature sensor on order, I'm sure I saw a link to one earlier in the thread but I can't find it now, so I'll check ebay...