Simon's new Xantia V6 and Leaf blog

Tell us your ongoing tales and experiences with your French car here. Post pictures of your car here as well.

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CitroJim
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Re: Simon's new Xantia V6 blog

Post by CitroJim »

All the best with the DIODE mod this weekend Simon :-D

My silencer turned up a good week early too.. have a look at the label. If yours is like mine it originated in the UK so there must be a stockpile of them here. Mine came from Luton.... Then went to Somerset and then came just a short way past Luton again!!!

Those wrap-around clamps may pose a problem in that the bolts may not fit through. Just grind them down in their centres and then they'll fit no worries at all...
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Mandrake
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Re: Simon's new Xantia V6 blog

Post by Mandrake »

Not quite sure where you're suggesting to grind Jim ? On the smaller wrap around clamps (like the one that came with my polish exhaust a couple of years ago) the problem was that the bolt itself fouled the tips of the flare on the pipes by a good 5mm... :roll:

I now have four clamps - the two different sizes from Citroen - 66mm (?) and 74.5mm, plus two 80mm clamps from ebay that look identical to the 74.5mm one that I bought as extras just in case.

One of the clamps definitely fits the muffler flange there so we're ok for that one - however I think it was the 74.5mm one that fitted that flange the best hence buying a couple more so I have one for the CAT flange. I think I should be able to get what I need out of these four different clamps... [-o< I'll probably end up using the 80mm clamp on the CAT and the 74.5mm one on the muffler!
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CitroJim
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Re: Simon's new Xantia V6 blog

Post by CitroJim »

Mandrake wrote:Not quite sure where you're suggesting to grind Jim ? On the smaller wrap around clamps (like the one that came with my polish exhaust a couple of years ago) the problem was that the bolt itself fouled the tips of the flare on the pipes by a good 5mm... :roll:
That's exactly it Simon and that's where mine fouled but not quite to that extent, it was only about a couple of mm.. Just grind down a crescent shape in the middle of the bolt so that it'll clear the flare and all will be good...
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Re: Simon's new Xantia V6 blog

Post by Mandrake »

DIODE modification completed. :)

I see that my old free homepage site in NZ that had a lot of my Citroen images including my diode mod pictures has finally gone down (8 years after I left the company and 4 years after they were bought out!) so I thought I'd take some new pictures today in case anyone else who hasn't done it before is looking to do it.

Here are the wires separated and a section of insulation stripped off each one:
Image

Diodes soldered in place:
Image

Self amalgamating tape to keep it moisture tight:
Image

Finished off with some insulation tape to pull the entire wire bundle neatly together:
Image

It's early days but it does seem to have made the ride more consistently good at the front, but only time will tell with an intermittent fault. :)

What baffles me about the nature of the diode fault on these is that while I understand how the diode being faulty prevents the electrovalve from operating properly, I'm never able to catch it red handed by doing a bounce test at the front - it always seems to be in soft mode when I do the bounce, yet I can tell while driving the car it is sticking in hard. How it can pass a bounce test but misbehave on the move I'm not sure - but both of my previous Xantia's were the same - adding the diodes definitely cured the intermittent hard ride at the front but they never failed a bounce test even before the mod! :?

In other news I had the Lexia on the car during a drive after the work I did today and I decided to look at the gearbox oil temperature again - even on a longish drive where I gave it some serious welly I could not get the gearbox temperature above 92 degrees, and within 1 minute of easing back to cruise it had already dropped to 88 degrees and after another couple of minutes as low as 84 degrees! Average cruise temperature was 86-88 degrees with moderate driving.

This is a world apart from the gearbox temperatures recorded on the Silver problem child - which could easily be pushed to beyond 105 degrees when given some welly, then after 5 minutes of cruising it would still be well above 100 degrees... :roll: (It's so obvious in hindsight that the heat exchanger must have been blocked)

It makes me really happy to see the gearbox temperature so low on this car, even when it really gets pushed... :)
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CitroJim
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Re: Simon's new Xantia V6 blog

Post by CitroJim »

That's a nice neat diode mod Simon :-D

I do agree it's good to see low gearbox temperatures. I remain a believer that running too hot does shorten their lives considerably...
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Re: Simon's new Xantia V6 blog

Post by xantia_v6 »

I would think it more likely that the transmission on your old car was running hotter because the lock-up clutch in the torque converter was slipping more, because the pressure was low, because the filter was blocked. I don't know if a blocked filter would also reduce the oil flow through the heat exchanger.
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Re: Simon's new Xantia V6 blog

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xantia_v6 wrote: I don't know if a blocked filter would also reduce the oil flow through the heat exchanger.
I think it might Mike... I do agree the slipping TC clutch would certainly dump more heat into the oil.

My first V6 had a blocked cooler due to many attempts to fix a leaky heater matrix. I still think this was a contributory factor in its failure...
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Re: Simon's new Xantia V6 blog

Post by Mandrake »

xantia_v6 wrote:I would think it more likely that the transmission on your old car was running hotter because the lock-up clutch in the torque converter was slipping more, because the pressure was low, because the filter was blocked. I don't know if a blocked filter would also reduce the oil flow through the heat exchanger.
I think I've reasonably ruled out slipping clutches as the cause of overheating for a number of reasons.

1) The clutches weren't actually slipping - if you listen to and watch the RPM carefully during acceleration in response to throttle variations it's pretty easy to tell whether the torque converter is unlocked, locked, or slipping. There was never any sign of the torque converter slipping when it shouldn't be (or other clutches) in fact that gearbox had a strong tendency for the torque converter to lock up abruptly and stay locked up a lot more than it should.

One of the reasons the low RPM pickup was so poor on that car later on is that even when you slowed right down it wouldn't unlock the torque converter until you were nearly at a standstill. For example you'd slow down to 15mph in 3rd to take a junction, try to accelerate away and it would remain in 3rd and the torque converter would stubbornly remain completely locked up even though it was causing the engine to labour at 1200rpm to try to pull up a hill. The new V6 is totally different in behaviour - the exact same junctions (which I travel every day) at the exact same speeds and as soon as I accelerate at the same slow spots it unlocks the torque converter immediately to let the RPM climb to 2000rpm or so which gives a good surge of acceleration thanks to the torque multiplication. As you speed up it then progressively locks the converter back up again at a certain threshold speed. In fact if anything the new V6 is much more eager to unlock the torque converter at low RPM and allow it to run in open mode, and an open torque converter is the major contributor to heat in the box.

If the clutches were slipping enough to cause overheating I'm certain that the ECU would have logged a fault and yet in 2 years and 1.5 years of trouble it never once logged a fault code for clutch slipping.

2) I'm not just going by the peak temperatures reached, I'm also looking at the cool down characteristics. If it did have a slipping torque converter clutch (or any slipping clutch) generating a lot of heat then it should still cool down quickly when the load came off, but it didn't. I could get it up from 95 degrees to 105 degrees in just a few minutes of hard driving, yet I could coast down a hill at 60mph with a good air flow and little to no throttle and 5 minutes later it would still be above 100 degrees - less than 1 degree of cool down per minute of cruise. That just shouldn't happen if the heat exchanger is doing its job when there is a 15+ degree temperature differential between the oil and coolant.

The new one not only doesn't climb as high in the first place (approx 14 degrees lower for the same driving conditions) it also cools down VERY quickly indeed when the load comes off, quickly reaching an equilibrium with the coolant temperature. You can see it dropping before your eyes on the Lexia. I timed two minutes for it to drop from 92 degrees to 86 degrees when going from hard acceleration up a hill to gentle cruise on the flat. The heat exchanger is very effective on the new one.

Could a blocked filter cause reduced oil flow through the heat exchanger ? Of course, since the oil pump is what pumps the oil through the heat exchanger. I'd have to check but I think the return flow from the torque converter is the path that then leads to the heat exchanger, since the torque converter is the major heat generator.

But could the oil flow be reduced so drastically due to a blocked filter to prevent the heat exchanger from working effectively, and yet not cause low pressure that causes the entire box to malfunction and clutches to slip ? I think that's very unlikely. It seems far more plausible to me that the coolant side was blocked, especially when the car had a split coolant expansion chamber that was loosing coolant and unable to pressurise. The chances of someone having put a stop leak potion in the coolant before I bought it in an attempt to fix the coolant loss is quite high.

Had I checked the gearbox running temperature, flushed/replaced the heat exchanger, replaced the coolant expansion chamber and given the gearbox a hot flush all as soon as I bought it, the car might have been saved, but I didn't have the knowledge or first hand experience at the time to have known to do that. And maybe it had already suffered too much damage before I bought it and its demise would have only been postponed. No way to be sure.

I'm not saying the heat exchanger was the only contributor to its demise or that there weren't other issues with the box, (after all the neck bearing seems to be what killed it) but I am pretty confident that the heat exchanger was blocked and basically not working at all.
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Re: Simon's new Xantia V6 blog

Post by CitroJim »

Simon, another piece of most interesting a thorough research :-D

All adds to the knowledge..

Was the cooling system on the old V6 generally healthy otherwise?
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Re: Simon's new Xantia V6 blog

Post by Mandrake »

It seemed to be. Once I replaced the coolant expansion vessel it completely stopped using coolant. (It went from needing a top up about every 6 weeks to not needing top ups at all...) I also never had any problems with the engine overheating...

But I'm guessing the heat exchanger works as a "bypass port" a bit like the heater matrix, so that if it gets blocked the coolant finds another way to flow ?
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Re: Simon's new Xantia V6 blog

Post by CitroJim »

Mandrake wrote: But I'm guessing the heat exchanger works as a "bypass port" a bit like the heater matrix, so that if it gets blocked the coolant finds another way to flow ?
Yes, that's correct Simon.
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Re: Simon's new Xantia V6 blog

Post by lexi »

Did you not get any goodies off that silver car? Expansion tank etc?
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Re: Simon's new Xantia V6 blog

Post by Mandrake »

A few goodies but not the expansion tank unfortunately! :evil:

Annoying, because although I haven't had to top up the coolant on the new one yet, it has a stain around the seam that shows it's only a matter of time until I need to replace it...(and according to receipts it has been replaced twice already!)
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Re: Simon's new Xantia V6 blog

Post by CitroJim »

Mandrake wrote:(and according to receipts it has been replaced twice already!)
That's pretty normal Simon, mine's has at least two, if not three..

They eat them for breakfast..

Oddly, the same tank is used on the 2.1TD and there it seems to be much more long-lived :?

A scrap 2.1TD will often yield a good tank...
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Re: Simon's new Xantia V6 blog

Post by Hell Razor5543 »

I wonder if, even if the operating temperatures are similar, the V6 generates more pressure in the cooling system (especially as they also have the automatic gearbox)? Could be worth investigating.