C6 auto gearbox woes

[Orbit Motors]

Evening everyone,

New member here, but the forum has come in use for a few things before as a visitor so I thought it was time I joined in and hopefully help others too.

I took a rather big risk today, and sure enough I got the sharp end of the stick soon after. I purchased a very nice looking 2006 Citroen C6 2.7HDi from an auction. I'm used to buying things at auction so I know the drill. No comebacks, and buyer beware. But luck was not on my side today at all. Soon after taking it for a drive and realising just how much I loved the rixe quality, build quality and general ambience of the C6, the auto gearbox became incredibly lurchy. And at the next set of lights I came to, decided it wouldnt go in to gear ever again.

Got a hand from a couple of passers by who helped push me to a more suitable location, and after a quick look around, I could see a pile of sludge forming on the floor that looks like a mixture of ATF and coolant, and there was a clear hose about a third of an inch in diameter hanging down which was where said mess had come from. All around the gearbox was the same sludge that looked just like what you get when your head gasket goes, so I'm making an educated guess that gear oil and water have mixed somewhere.

Having got the car off the road to a suitable place to keep overnight thanks to a kind gent in a Range Rover, I have done some investigation and it would appear to be that a good place to begin looking would be the hear exchanger / oil cooler that is attached to the box. Are these a common point of failure and how likely is it that I can somehow get this changed and save the box and cooling system by flushing them out? The price and labour for a replacement box is making me feel sick just thinking about it!

If anyone has any other pointers or places to begin looking, please let me know. Really hoping I can save it!

[GiveMeABreak]

Hi and welcome.

David had what looks like the same issue - the gearbox oil cooler failed. Have a read of his blog concerning his C6, what happened on bringing it home and his fix here:

viewtopic.php?p=624799#p624799

[Orbit Motors]

Hi and welcome.

David had what looks like the same issue - the gearbox oil cooler failed. Have a read of his blog concerning his C6, what happened on bringing it home and his fix here:

viewtopic.php?p=624799#p624799

Sounds very much like my issue!

I had an eye watering quote of £2500 for a new box and torque converter (why that would need changing I don't know) from somewhere in Huddersfield, who have a 100 mile radius for work which I just fit in to.

Tried a couple of other places who claim to specialise in auto boxes and they don't want to touch it...

[GiveMeABreak]

The AM6 box is generally very reliable itself. it’s an AISIN Warner transmission and used under various names by many manufacturers. The gearbox cooler is another issue though. I would be focusing on getting that sorted before looking at the box itself. If it’s still faulty afterwards then it may be the hydraulic block, which again are repairable by gearbox specialists. A proper diagnostic with a Lexia is your best bet for troubleshooting though.

[Orbit Motors]

Rather inconveniently my Lexia / Diagbox has stopped working for some reason recently so I need to find out why... it never rains but it pours!

An update on the car however, I slept on it and decided to think with a clear head the next day which the weekend has given me a chance to do. I've decided to persevere and I'm having it recovered to my friend's unit and we are intending on repairing the transmission and the other issues that have since come to light (although I think the garage went a bit overboard with some things so I want to take a look myself anyway).

Are the coolers themselves replaceable with something more reliable or is there a common reason for failure such as incorrect/old antifreeze? And are they seated directly to the box or do they have a gasket of some kind that is prone to failure?

Sorry for all the questions, never dealt with automatics before much at all other than driving them. Just looking forward to getting her fixed up to use as a daily!

[GiveMeABreak]

The official oil cooler / exchanger part is still available. I think another member replaced his with a different type on his C5. Have a look at Elis's post on his oil cooler modification project:

viewtopic.php?t=59465

[Jay-Bruce]

Hi Marc, I love the way you have a link at hand for every previous thread pertinent to the current topic, it's a real skill.

Edit: Should have read page 1 instead of skipping to "Actual Project begins page 4" - this is the ultimate solution for cooling

[jml]

Can I just take this opportunity to give a big thumbs up to the Aisin AM6 box and, just from my perspective, comment on a couple of the frequently raised points.

I have a C8 with the twin turbo 2.2 HDi 173 hp unit, with the AM6 box, like some C6s. Like others, I was a little sceptical about the ‘sealed for life’ claim about the box but only did something about it at around 120,000 miles. Not having a Diagbox at the time, I put it into a well respected autobox specialist to change the oil, however they used the incorrect oil. Nevertheless, the old oil that came out was remarkably clean and uncontaminated so, just based on my experience, I don’t see the need to replace the fluid too frequently. I’m now at 183,000 miles and plan to change the fluid before too long, although the box is performing perfectly at the moment.

When I’ve removed the level, drain and filler plugs they all came out without difficulty.

I tend to use the manual function a fair bit and, living in a hilly area, I frequently downchange manually for engine braking - whether my usage pattern has helped things, I know not !

I’ve read quite a few reports of the failure of the gearbox oil heat exchanger and have a spare one available just in case but, so far, everything about my car has been amazingly reliable. (I just hope that I’m not tempting providence !) I’ve owned it virtually from new and always pampered it and there’s virtually nothing, other than maintenance and reasonable wear and tear items, that my car has needed. I don’t think there are many 14 year old cars with over 180,000 miles that can claim that.

My time with the car may be limited as I have terminal cancer but I’d love to see it past the 200,000 mark

Cheers

Julian

[myglaren]

Very sorry to hear that you have terminal cancer Julian.

[jml]

Very sorry to hear that you have terminal cancer Julian.

Thanks for that, I’m very upbeat about it and determined to fight the bloody thing for as long as possible. Two years ago they said I might only have a few months so I’m doing ok and I’ve got all sorts of targets. 200,000 on the car is one of them

Cheers

Julian

[Jay-Bruce]

I echo Steve's thoughts, I'm really sorry to hear you've caught a one way ticket, but I've got to say kudos for being so upbeat about it.