All Things V6...

[white exec]

Must say, I feel the same way. Two OE (Valeo aluminium) oil coolers have given way here, filling the cooling system with engine oil each time. Enough.

Car now fitted with a Setrab air-oil cooler (radiator), with a sandwich-type take-off in place of the original.
The new cooler is fitted ahead of the main radiators, in the nosecone. Has been on the car for 9 years now.

All the bits, including braided hoses, from here:
http://thinkauto.com
They're in Ashford, Middx.

Maybe worth looking at.

[Stickyfinger]

Is removing the combination pre-warmer/heat exchanger a good thing for David ?...remembering he lives in a place that is cold much of the year ?

How will that effect the boxes performance on a cold morning ?

[white exec]

A thermostatic take-off is listed, if required, to avoid over-cooling.

[Stickyfinger]

But then (my point) the warming of the box oil from the engine on very cold days does not happen.....

[Mandrake]

But then (my point) the warming of the box oil from the engine on very cold days does not happen.....

Except by heat generated by the torque converter ?

An open torque converter generates a LOT of heat, that's one reason to have torque converter lockup in the first place. (The other being fuel economy)

An automatic gearbox can work fine at a lot lower than the nominal 80-100C that they are usually subjected to by piggybacking them onto the engine coolant system. In fact after having first hand experience of a failed Xanita V6 gearbox that was destroyed by overheating, (from a blocked heat exchanger) I would say the "normal" operating temperature is at the very upper limit that the gearbox and oil can withstand over long periods of time! A blocked heat exchanger only raises the oil temperature by about a further 15 degrees but that is enough to burn and blacken the oil over only a few months leading to ultimate failure.

My opinion is a much lower temperature in the 40-60 degree range is more optimal, certainly from the point of view of reducing the stress on the oil, which already has a very hard life in an automatic gearbox. If the cooling system of an auto box was decoupled from the cooling system of the engine and the engineers could choose any operating temperature they liked I guarantee it would be a lot lower than coolant temperature. It's piggybacked onto the coolant system for expediency, nothing more.

Also keep in mind that ATF is very thin even at low temperatures, and that the gearbox still spends a lot of time operating at lower temperatures because despite the heat exchanger helping to warm it up initially it can still take 20-30 minutes of spirited driving (at least on the Xantia V6) for the oil to reach 80+ degrees as the gearbox has a lot of thermal mass relative to how much heat the heat exchanger can put in or remove.

The sump is also designed with a calibrated leak levelling system to compensate for the change in oil volume with temperature. In short the gearbox is perfectly happy operating at say 60 degrees instead of 90 degrees and will thank you for it.

I like Chris's idea a lot - if I was implementing it I would aim for a target temperature of around 40-60 degrees - if the oil temperature is below 40C I would use something like a solenoid to bypass the oil around the cooler and if it went above say 70 degrees I would wire it to bring on the radiator fans for extra cooling.

[Zelandeth]

Failing that, there are better oil to water coolers.

The one on the auto Saab 900s lives in the lower radiator hose between the rad and the engine...have never heard of one failing...

[DHallworth]

Well, I've bitten the bullet. The car isn't here so I can't spend any time looking for a solution and I can't ask other people to do it so I've ordered an oil cooler.

Citroen Glasgow had it in stock on the shelf. Apparently they've sold 4 of them this year.

I managed to get it for £320 + VAT. Still a horrendous amount of money but needs must.

Does anyone know if there's a way to use service box to find out which models of car a part was fitted to? I'm looking for a driveshaft. Part number is 3273WY but am unsure if it's unique to the 3.0 HDi or not.

David.

[white exec]

You do have to ask why they've sold four this year . . .

When my original Valeo aluminium oil cooler failed in the 2.5 (after 6 years and 80k miles) my immediate reaction was to replace it with a new one. Did just that (at around €400; was available only from Citroen), but was shocked to find that this one lasted just 5 years more, and only 5k miles!!

After reading other accounts of similar (and yet another just this week), I decided enough was enough, and I wasn't prepared to undergo a repeat - and all the cleaning out that went with it. In my case, an oil-filled cooling system was all (!) that resulted, not a ruined auto transmission. My guess is that it was inherently poor construction, and an inability to run with even top-notch and scrupulously maintained (Citroen) coolant.

Agree with Simon's comments above. ATF is thin stuff even when cold, and has no need to run at best part of 100ºC. Cars have run with air-oil coolers on their gearboxes for many years, but there are cost savings in fitting these cheap and compact oil-water exchangers. I agree again with Simon that the contribution of heat from the coolant to a cold gearbox is exaggerated; the box is quite able to supply its own heat.

[Stickyfinger]

Gents, thanks for the education on gearbox temps.

I now have to look for a system to fit the Activa.

[DHallworth]

Manuals run at much lower temperatures then auto’s do so personally i wouldn’t bother looking to do anything with my Activa

[xantia_v6]

I now have to look for a system to fit the Activa.

As your activa has neither an engine oil cooler nor transmission cooler, you should not be too worried about coolant contamination...

[RichardW]

Does anyone know if there's a way to use service box to find out which models of car a part was fitted to? I'm looking for a driveshaft. Part number is 3273WY but am unsure if it's unique to the 3.0 HDi or not.

David.

Yes, select a car (any will do) then there is a Search box top right above where the list of parts is - stick the part number in here, then hit search. Under C6 it comes up with:

You can then click on the bit ringed, and it will show you a list of other vehicles, in this case

And then click on C5 which shows

[GiveMeABreak]

Well, I've bitten the bullet. The car isn't here so I can't spend any time looking for a solution and I can't ask other people to do it so I've ordered an oil cooler.

Citroen Glasgow had it in stock on the shelf. Apparently they've sold 4 of them this year.

I managed to get it for £320 + VAT. Still a horrendous amount of money but needs must.

Does anyone know if there's a way to use service box to find out which models of car a part was fitted to? I'm looking for a driveshaft. Part number is 3273WY but am unsure if it's unique to the 3.0 HDi or not.

David.

David, that part is only for the DT20 (3.0 HDi) engines on the C5 X7 and the C6.

[Stickyfinger]

Manuals run at much lower temperatures then auto’s do so personally i wouldn’t bother looking to do anything with my Activa

You can get them hot David

To be honest, I would rather not bother as oil changes are cheaper if I have been "spirited".

[DHallworth]

Well, today has been a day with a little bit of progress...

I managed to source a driveshaft from a breaker in The Netherlands which should hopefully be here whilst the gearbox is being changed so it can be put back in instead of the original one which would be handy.

I've also out that nobody replaces the oil cooler on these gearboxes when they are rebuilt and knowing what carnage takes place when they have failed, there's no way I'm spending £2.5k on a gearbox rebuild and taking a chance on a 2nd hand cooler.

The only place I can find the oil cooler for these cars is from Citroen. What's even more surprising is that the local dealer in Glasgow had one in stock and on the shelf. What's worrying is that one dealer have sold 4 of them this year.

Annoyingly though, they don't stock the o-ring that goes behind it so I've had to order that and will need to go back for it.