Simon's new Xantia V6 and Leaf blog

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Mandrake
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Re: Simon's new Xantia V6 blog

Post by Mandrake »

white exec wrote:- to keep it clean, maybe? I presume it's just a NTC or PTC resistor. Be interesting to compare the resistances of all three (when you have the new one), and see if they're the same at the same temp. Wonder if a replacement needs calibrating, or whether the ECU somehow does that itself (not sure what it would check it against).
The sensor is just a standard two wire NTC as the resistance goes down with temperature increase.

They don't really need calibrating from one sensor to another - these kind of sensors are better than 1 degree without requiring calibration and 1 degree is fine for this application - the experimental measurement errors from factors like the heat of the air filter box influencing the reading would be an order of magnitude worse than the tolerance difference between two sensors I suspect.

I don't think I have the original factory sensor with the broken tabs, I think I binned it, but I'm pretty sure they'd all read almost the same under static conditions, the difference is going to be the reading when the air filter housing is hot and the incoming air flow is cold - the open design of the one I just ordered should in theory read much lower (and closer to the real air temperature) in these circumstances while the one fully within the plastic sleeve will read a lot closer to the temperature of the housing.
Wonder what would happen if the sensor were moved right "down front", so it was actually measuring the atmospheric air intake temperature.
That's not necessarily the answer - because what you really want is the air temperature just before it goes into the cylinders. That's what matters for calculating the charge of air inducted into the cylinders. Some of the temperature rise recorded by the sensor is actual heating of the air - I think a temperature rise of 20-30 degrees above ambient is normal when the engine bay is really hot due the air flowing through hot ducting, a hot air filter box, a hot intake manifold etc... putting the sensor right at the front before it has even gone through the air filter box would record a temperature that is a lot lower than how warm the air is by the time it has reached the valves in the engine.

But a temperature rise of 53 degrees above ambient is just not believable to me, especially when I've checked this reading on my old V6 on the Lexia many times and never saw the air intake temperature reading go above about 40 degrees even when the engine bay was stinking hot. So I think this current sensor is reading up to 25 degrees too high when the filter box is hot due to it not being cooled by the air flow properly.
Agree with your point about suddenly changing air flows, and a sensor with thermal lag. Doesn't make much sense, having the engine respond to conditions that no longer exist!
The thermal lag of a sensor that is basically insulated by the plastic sleeve will be quite bad - the original sensor probably performs a lot quicker, and I'm hoping the one I've ordered will perform even better again as the sensor bulb is completely out in the open in the air flow with little direct conductivity back to the housing.

Modern MAF sensors which work on the heated wire principle work by heating a thin wire filament and then measuring the temperature drop of the filament caused by the air rushing past, which also requires an accurate measurement of the air temperature before it gets to the heated wire filament. By knowing the incoming air temperature and measuring the temperature drop of the heated filament you can calculate the air flow, the greater the air flow the more the heated wire cools. These type of sensors are extremely susceptible to carbon and dirt build up on the filament, which acts as an insulating medium, when they get dirty like this they don't see nearly the same amount of temperature drop which translates to the MAF sensor thinking there is less air flow than there really is - you then have a dirty MAF.

This air temperature sensor likewise will not drop in temperature as much (from the "ambient" temperature of up to 65 degrees inside the filter housing) when exposed to cold air flow if it is insulated instead of being exposed. The more it can be exposed to the air flow and the less thermal conductivity there is from the sensor back to the housing (through the base of the sensor) the more accurate its real world reading will be.

The symptoms of the insulated sensor would be that when the engine bay starts off cold the air temperature sensor will give an accurate indication of incoming air temperature and things will be fine, however as the engine bay gradually heats up and the air filter box gets hot the reading will start to increase well above the true air intake temperature reading, this will cause the engine to run progressively leaner and leaner (in open loop mode) due to the false high temperature reading.

So in theory replacing the sensor should make little difference in a cold engine bay but the engine performance should not deteriorate as the engine bay warms up.

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white exec
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Re: Simon's new Xantia V6 blog

Post by white exec »

Agree with all that. Worth using the 'open' sensor, and maybe thermally insulating it (insulating sleeve?) from the hot box it's normally latched into. Ideally, this sensor would have minimal body mass*, and therefore very litttle thermal lag. Will be interesting to see how much effect all this has on performance.

* This could be done, experimentally, by simply substituting an electrically identical NTC bead, and running this instead of the heavy-bodied OE sensor.

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Re: Simon's new Xantia V6 blog

Post by Mandrake »

Well at 19 years old I suppose it had to happen, but I now have a leaking heater matrix! :(

I noticed the passenger side mat was quite wet, and as I drive the car without a front seat passenger during the week it shouldn't be wet feet...I tasted it and sure enough it tastes bitter, and I can actually see a drip hanging from the join at the bottom of the heater box. I laid out some kitchen roll on the floor during a couple of drives to the recycling centre and sure enough it half soaked the piece of paper. :evil:

Coolant level is still visible but about an inch below where I normally set it - and I am reminded of the fact that there is NO working coolant level warning on a S1 V6. [-X

As the car is now used on my daily commute to take my 9 month old son to his gran's, before catching a train to work this is quite a serious problem for me. I CAN at a pinch get him there by bus and train for a few days but it is a complete ball ache to do so, so if I take the car off the road to change the matrix it really needs to be started and finished on the same weekend come rain or snow.

I'm really dreading the prospect of this job especially mid winter as I know what a hassle it is to get the dashboard out - I've had a Xantia dash out once but it was 12 years ago so all the small details of where bolts are etc is long forgotten, and it was done without the pressure of time and winter weather.

So a little help would be appreciated - the first thing being what is the recommended brand of after market heater matrix and roughly what am I up for ? I remember reading about certain "cheap" brands of matrix that just leak again, I do NOT want that happening just to save £20 or so off a better one, but on the the other hand I don't want crazy expensive either.

The other thing is has anyone done a full guide of how to get the dashboard off and back on again with a screw/bolt location guide ? I'm usually decent at getting things apart but I sometimes have trouble remembering where every screw and bolt belongs on reassembly! :lol:

As its a Series 1 with an air bag the steering wheel will have to come off - any advice on how to do that without damaging the rotary contacts would be appreciated.

Surely after a new radiator and heater matrix it won't spring a leak on me again ? :(
Last edited by Mandrake on 15 Jan 2017, 16:08, edited 1 time in total.

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Hell Razor5543
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Re: Simon's new Xantia V6 blog

Post by Hell Razor5543 »

I seem to recall that the Valeo matrix are considered to be very good, and that you should also use Forte Stop Leak after fitting the matrix (I believe that Valeo insist on it for the warranty). More than that I don't know (but I bet CitroJim will).

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Re: Simon's new Xantia V6 blog

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Hell Razor5543 wrote:I seem to recall that the Valeo matrix are considered to be very good, and that you should also use Forte Stop Leak after fitting the matrix (I believe that Valeo insist on it for the warranty). More than that I don't know (but I bet CitroJim will).
I'm reluctant to put any kind of stop leak in the system due to the gearbox heat exchanger - I know it's not blocked at the moment (gearbox oil temperature is normal) and I don't want to risk changing that, even with something "safe" like Forte. I would have thought that if I replace a faulty matrix it shouldn't need any stop leak goo.

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Re: Simon's new Xantia V6 blog

Post by CitroJim »

Hell Razor5543 wrote:I seem to recall that the Valeo matrix are considered to be very good, and that you should also use Forte Stop Leak after fitting the matrix (I believe that Valeo insist on it for the warranty). More than that I don't know (but I bet CitroJim will).
Yes, I can recommend it. It's so far keeping Gabriel's weepy matrix under control...

I have a GSF matrix in stock ready for the job and it looks to be a very well made German one...
Mandrake wrote: I'm reluctant to put any kind of stop leak in the system due to the gearbox heat exchanger - I know it's not blocked at the moment (gearbox oil temperature is normal) and I don't want to risk changing that, even with something "safe" like Forte. I would have thought that if I replace a faulty matrix it shouldn't need any stop leak goo.
I'd not have any concerns about using Forte Stop leak at all Simon. As James says, Valeo insist on it... Such a company as Valeo are not going to say that lightly or risking lots of trouble from cooked transmissions...

Forte is not like a traditional sealer at all. It looks and feels like very thin milk and works on the clotting principle... A bit like liquid latex tyre sealants as I use in my bike tyres. I believe it contains very tiny bamboo fibres. It has no solids in it unlike Radweld or K-Seal which I definitely DON'T recommend at all. I've seen the results too many times. I've had systems all in bits that have run Forte and not seen any adverse effects, unlike I've seen with the others.

Go ahead and use Forte with confidence Simon. It may just stave off the matrix job until time and weather permits...

Also, be happy that the S1 V6 is one of the easier ones to do due to the easy accessibility of the matrix elbow connector :)

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Re: Simon's new Xantia V6 blog

Post by Mandrake »

Hi Jim,

Is this the correct one, and the correct quantity for the V6 cooling system ?

https://www.amazon.co.uk/Forte-Lubrican ... B0035PU52U

If you're sure its OK in the V6 maybe I should put some in to hold it at bay until I can get a matrix and the right time to replace it. Either way I don't have much choice but to keep driving the car and checking the coolant level.

Is it the kind of stuff that removes completely when the system is drained and refilled after the matrix swap - eg it won't leave anything nasty baked in the system forever ?

Another question - can it be added via the expansion chamber ? If I did, would I have to drain the chamber dry first so that it would mix with the rest of the system rather than just float in the dead end that is the expansion chamber ? Or is it not a dead end with the small pipe on the front ?

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Re: Simon's new Xantia V6 blog

Post by CitroJim »

That's the one Simon. I know it's expensive but worth every penny. Shop around a bit and you may find it a little cheaper.

One bottle will do, no more than that is needed. In fact in Gabriel I have about half as I used half a bottle originally and then used the other half when I did the cambelt, water pump and coolant change.

I am so confident that it'll be absolutely fine that if it isn't I'll buy you a new transmission cooler and offer a free HP20 overhaul... I nearly said I'd give you my Activa but even I have my limits ;)

I've used it in V6s with no issues and as I say, every system I've drained and stripped that I know has used it I've never seen a trace of it.

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Re: Simon's new Xantia V6 blog

Post by Mandrake »

Well I've ordered a bottle - £14.95 inc delivery, should get it on Tuesday at work. Fingers crossed that it works well enough to stop it leaking for a couple of months!

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Re: Simon's new Xantia V6 blog

Post by CitroJim »

Fingers crossed here too Simon...

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Re: Simon's new Xantia V6 blog

Post by Hell Razor5543 »

Nice. Jim, did you spot the extra question at the end of Simons' 'checking' post, about adding the Stop Leak via the expansion chamber?

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Re: Simon's new Xantia V6 blog

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Hell Razor5543 wrote:Nice. Jim, did you spot the extra question at the end of Simons' 'checking' post?
Missed that :oops: Thanks James :)

Yes, if need be, drain out a bit of coolant from the expansion tank. Or rather than draining, just use a turkey baster or similar to suck some out...

Then add the Forte but ensure there is enough coolant removed to ensure that none of it can be lost through the overflow when the system is up to temperature and pressure... You don't want the level anywhere above the mid-point of the tank (i.e the top of the internal framework) or you will loose some out of the overflow.

It will soon circulate as the coolant in the expansion tank is by no means static or stagnant... There's a decent flow going on...

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Re: Simon's new Xantia V6 blog

Post by DHallworth »

The matrix on my Activa started leaking about 3 weeks before I made the trip to BL for my V6 conversion. Thankfully I managed to get that onto the list of jobs to do whilst it was in the workshop.

Bill also took his V6 from up here to have his matrix done there too.

If you're pushed for time and need it done quickly, have a weekend away and book it in :) One way of guaranteeing it's done right and back together quickly.

David.

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Re: Simon's new Xantia V6 blog

Post by RichardW »

I put Forte in my HDi as a temporary measure till I could get to the matrix. It was still there when it went to the scrap yard about 75k later; and still sealing the matrix :lol:

Let me know when you want to do it, I'll come and laugh, er, no I mean help!!

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Re: Simon's new Xantia V6 blog

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RichardW wrote: Let me know when you want to do it, I'll come and laugh, er, no I mean help!!
You two together would get the job done in a day, no problem at all :wink:

It's certainly a job that needs assistance.