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

[Stempy]

Does that mean and end to this thread finally? Or will we one day have a post from a chap in Iran about swapping ECU's?

[Northern_Mike]

I believe he's already created a username

Sent from my SM-N9005 using Tapatalk

[KP]

Has he indeed? Care to share?

You never know, the amount of new parts in the car it should carry on going.

[Mandrake]

Well that's a bit of an inauspicious end to the car, and certainly not one I anticipated...

Did you pass on the CPH code I gave you Will ? It doesn't have the original CPH/ECU fitted so if they try to strip those for parts they'll find that the CPH code they get from Citroen based on the VIN number won't work...

SAIPA produced the Xantia in Iran right up until the end of 2010 so there may well be a market for parts there or even getting the whole car back on the road by overhauling or swapping the gearbox... It's amazing how in some countries cars will be repaired and kept going for years or even decades longer than in throwaway countries like the UK that look down their nose at a car over 10 years old.

[KP]

Yeah I have them the envelope with all in Simon

Also explained to them about mackies in Glasgow and that the box should have it's filter and fluid replaced as a matter of course with the correct fluid as well

Be a shame if it gets broken for parts but one thing I'd buy back off them would be the cat as it's a little monster and would do my turbo as well with a little work but also allow better flow I feel
They wanted to buy my other V6 and my Activa as well! I did say the activa wouldn't go and gave them a price for the V6 once I had sorted it's niggles to a degree I was happy with and they are going to get back to me.

To be honest I think if they are worth good money over there it wouldn't be too much to stick a towing dolly on one and take two over on a few day drive there and then fly back

[DHallworth]

To be honest I think if they are worth good money over there it wouldn't be too much to stick a towing dolly on one and take two over on a few day drive there and then fly back

4187 miles or 74 hours driving according to Google Maps. They'd have to be worth a bloody fortune for that to be viable!!

David.

[KP]

They could well be and don't forget you could do that with just two night stops and fuel across the water gets cheaper as you get closer...

[Mandrake]

I wasn't sure which of my threads to post this in but decided to post it here.

I think I've now figured out with some certainty what caused the old gearbox to fail - not the nature of its final demise so much (which we think is torque converter neck bearing failing) but rather the underlying fault that led to it's rapid demise from seemingly being ok to nearly dead over only 2 years and 12k miles... Jim can probably guess the cause - blocked heat exchanger...

We've speculated about this being the underlying cause before but without any real proof as I never took the hoses off and tested it for flow. I now think I have that proof.

Several times with old V6 I've had the Lexia on the car monitoring the gearbox oil temperature for prolonged periods of time while driving, so I have a pretty accurate idea of just how hot the oil got under fairly controlled conditions around my favourite "test track" roads etc.

I've previously commented that I thought the oil was getting too hot, and that it seemed to get hot quickly and was VERY slow to cool down again. In theory the heat exchanger should keep the gearbox oil within a few degrees of the coolant temperature once equilibrium is reached, however that was not happening.

Under hard acceleration and spirited driving on country roads the temperature would settle well over 100 degrees, typically it would hover around 105 degrees when pushed but I've seen it peak as high as 108 degrees.

Not only that but after getting the oil that hot even if you eased right off and coasted down a hill at 60mph (plenty of air flow through the radiator) the oil temperature was not dropping significantly - it might go from 106 down to 104 after a couple of minutes coasting for example, even though the coolant temperature was say 92 degrees at the time, and would not go below about 102 degrees while continuing to drive.

I wasn't happy with the above but had no other V6 to compare the figures with at the time...

Today I did my first extensive test of gearbox oil temperature while driving, monitored on the Lexia, on the new V6, and the difference is very stark indeed.

I put it through all the same test roads that I follow and I pushed it HARD. After it was already fully warmed up I gave it two hard runs up a long steep hill in a row - more or less full acceleration from stationary to three figure speeds. At no point did I ever see the gearbox oil temperature go above 94 degrees!

In fact it was staying between about 87 and 94 degrees with 91 degrees being typical. Not only was the temperature much lower, it was cooling down MUCH quicker when easing off the acceleration. For example it might peak at 94 degrees after a fast run up the hill, when I turned around and coasted down the same hill at 70mph within about one minute the temperature dropped back to about 88 degrees, which did NOT happen on the old V6 where coasting hardly cooled it at all and it might still be sitting at 105 degrees a few minutes later.

I also noticed that with gentle driving the gearbox oil temperature tracked the coolant temperature fairly closely, eg driving slowly in an urban area where the coolant will warm up enough to trigger the fans also raised the gearbox oil temperature to about 92 degrees, but then coasting at 60mph with a light throttle would quickly bring the gearbox oil temperature back down to about 88 degrees - due to the coolant also being cooler at the higher speed.

So the average and peak oil temperatures of the gearbox in new V6 are about 14 degrees cooler than old V6 - average 91 versus 105 and peak 94 versus 108. The evidence is clear - the heat exchanger on the old V6 was not working, probably completely blocked. It can't have been the oil side blocked or there would be no oil pressure,so it must have been the coolant side.

14 degrees might not sound like a huge amount but what I've read is that a 10 degree increase in oil temperature in an auto box can literally halve the life of the box. A 14 degree increase over design temperature is almost certainly enough to burn the oil and overheat the lockup clutch in the torque converter as well.

Here's my theory of the demise of this gearbox:

Some years ago the coolant expansion tank seam started leaking pressure (as they do) and instead of replacing it someone threw some stop leak in the coolant... It might have stopped the leak (for a while anyway) but it also blocked up the heat exchanger.

If driven only for short trips or driven conservatively the oil temperature doesn't get dangerously high - only when driven hard for prolonged periods of time is the heat exchanger essential to keep the temperature below 100 degrees.

I bought the car and started driving it hard, fairly often, so the gearbox oil started to get badly burnt due to the high temperatures that I was unaware of. An 800 mile trip around Scotland probably didn't help either. The high temperatures and burnt oil caused or contributed to the torque converter clutch starting to burn up and start shedding particles and everything went downhill from there.

The moral of the story is CHECK THE HEAT EXCHANGER!! Either by physically checking for flow through the coolant side (difficult) or by measuring the oil temperature during a prolonged hard run. Don't let your Xantia V6 die for the same reason this one did...

From what I can see the temperature shouldn't go much above 95 degrees, and anything over 100 degrees would be considered very suspect.

It also explains another symptom I had noticed with old V6 - when really hot and warmed up the gearbox would always try to keep the torque converter clutch locked up as much as possible (over temperature protection SK map) causing a lack of pickup when accelerating - it does this to let the torque converter and torque converter clutch cool down, but because it was overheating it was doing this frequently, more or less every time you went for a long drive.

I have not noticed this same tendency to try to lock the clutch up all the time when hot on new V6 and the reason will be that the temperature reading is 14 degrees lower and thus not triggering the over temperature protection SK map in the gearbox ECU...

It certainly gives me a lot more confidence in the gearbox in new V6 now I've seen that even when pushed really hard the oil temperature doesn't go over 94 degrees - it gives me confidence that the heat exchanger is working properly!

[KP]

Good right up and explanation Simon

My trip home from yours with gusto was probably the final push over the edge it needed and from that it was only a few weeks till death did us part

[Hell Razor5543]

Well Simon, Jim says that if you have a coolant leak you must only use Forte Stop Leak, as anything else clogs up the heat exchanger on the gearbox. I even remember a somewhat heated post with 'Falling-out-with-my-car' about it;

http://www.frenchcarforum.co.uk/forum/v ... ge#p344779" onclick="window.open(this.href);return false;

[CitroJim]

That's incredibly interesting Simon and a piece of excellent research. Well done It completely bears out my belief that it was precisely that which caused the gearbox in my old original V6 to fail. In that case the matrix had gone and the amount of leak stopping potions in the cooling system was legendary!

The cooler was definitely blocked and I was glad we damaged the rad lifting he engine out. later I found no end of silty residue in the expansion tank and engine block...

New coolers are terribly expensive. last time I checked they were over £250

James, yes. that's the only stuff I'd use but in an automatic I'd be a bit wary even with that, especially now with your research Simon!

With a good cooler just getting to oil up to 80 degrees to check the level is bloody hard going...

[KP]

That would be a bugger to rinse that all out as well I'm betting

[Hell Razor5543]

Something to remember here, Jim, is that Valeo insist that, for the warranty to be valid, you must use Forte Stop Leak when replacing a heater matrix. I would be very surprised if a recognised parts manufacturer would make such a demand if they felt it could cause damage to other components.

[CitroJim]

Something to remember here, Jim, is that Valeo insist that, for the warranty to be valid, you must use Forte Stop Leak when replacing a heater matrix. I would be very surprised if a recognised parts manufacturer would make such a demand if they felt it could cause damage to other components.

That's true enough Will,

I'm just going into ultra-conservative mode here (small c ) and I firmly believe it's easier and cheaper to replace a matrix than it is a gearbox...

[KP]

Just a ponder but could another heat exchanger not be used at all?