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2006 CTT Leaking transmission seal. Preemptive coolant tube replaceme

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Situation: 2006 Cayenne Turbo with 37k miles is leaking ATF from the holes under the bellhousing. Dealer replaced transmission valve body 2-3k miles ago, and I assume fill level is/was correct, but have not checked -- I probably should do that, but based on my prior experience with a fluid change, overfilling the Cayenne trans seems unlikely/difficult -- underfilled seems much more likely. The transmission shifts fine now.

To my knowledge, the coolant tubes/tees are still original/plastic. I have not smelled coolant or received a low coolant message. I'm debating whether I should bite the bullet and get the coolant tubes done at the same time. Based on reading other posts, it seems that when the coolant tubes go, I'll likely have to replace the transmission seal again. I only drive 7k miles/year, so I may be able to get away without this for another 3-5 years (possibly longer than I own the car).

Questions for the brain trust:

1) Anyone had an issue with just the transmission seal that was NOT related to the coolant tubes? Anyone ever heard of an overfill situation blowing out the seal on a Cayenne? Or is it most likely a slow leak of coolant from the tubes?

2) If it was your car/money, would you do the coolant tubes/tees at the same time, or take the gamble on doing all this again?

3) What else would you do while the transmission is out? Any other seals, lines, bushings, etc?

4) Does the transmission need to be drained/opened for the seal repair? Given that the trans valve body was just replaced, filter is new, etc., I'm thinking I should ask the mechanic to leave the filter alone and just top off the fluid if possible. That said, I've got a case of 3309 ready to go, if needed.

5) Appears that others have spent anywhere from $1300-$2500 for the transmission seal alone. Tips or thoughts from those that have been down this road? Is there any potential time/labor savings by doing the trans seal and coolant pipes at the same time?

Thanks for the responses!

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I would think if you plan on keeping your Cayenne for a while then get it done. It is only a matter of time, and miles until if fails. You can now pick the time and place to get the repair done. If you don't it may fail at a very inconvenient time and like you said, it could damage the seal. With the transmission out that is a perfect time to get at the plastic Coolant Tee's from the back side of the engine so I would do them together. If you haven't done the Coolant Pipes themselves, they're a ticking time bomb for a guaranteed failure. Even if you don't plan on keeping it too long it is a selling point for many knowledgeable potential buyers to having it done. If you have a shop do it all though you will probably not get your money back in the short term. I think the Coolant Tee's & Pipes failure is not just based on mileage but exposure time to heat and age have a factor too. Your low mileage for a 2006 helps but your probably not too far away from failure. I did the pipes 5yrs ago on my '06 CTTS as a preventative, and that was before everyone knew about the Coolant Tee's, well a few weeks ago one of my Coolant Tee's went.  Thankfully I was able to drive it home and I'm now finishing up the replacement, including a few vacuum lines on top of the motor which get brittle with age (Porsche did use some real cheap plastic vacuum lines). With the tranny out it is easy to replace your front O2 sensors but with your relatively low mileage I'm not sure I would do them. If they do the seal I think since you have the fluid I would go ahead and do a fluid change, it is a small cost compared to the overall work that would be done. Lot's of good opinions on here and a lot of people with similar experiences to yours so give it a day or so to see what some others say too.  Good luck, when there running good they are fun. And with all of this work done your Cayenne's long term reliability will be much improved.

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Thanks, Hahn. I checked and confirmed the following:

1) Picture at back of engine confirms I still have plastic pipes -- that's what I'd figured, but never confirmed as I've only owned it 10k miles and just assumed it was still plastic given the mileage. I thought maybe I'd get lucky. Oh well...

2) Coolant reservoir is below the low mark in the tank, but I'm not getting a warning light. Not confirmatory as most of my cars have always "consumed" a bit of coolant, but in this case it lends credibility to possible early failure of the pipes.

I agree with your recommendations. Also, my experience with other vehicles and maintenance intervals suggests that my location (Houston - HOT!) and driving style tends to result in earlier than normal replacement cycles. Tires, brakes, and bushings seem to go quicker than most. Makes some sense the pipes could go early too.

I'd planned on doing the pipes myself (someday) to save some money and have the satisfaction of knowing it's done right. But I may just throw cash at this one and be done with it. Too many projects right now.

Thanks again. Other opinions welcome.

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  • 5 weeks later...

I preemptively did the coolant pipes and turbo tees this weekend. Royal PITA. Followed the ECS Tuning writeup for the pipes. Tees are what the are -- you see them once you get back there -- but space is limited. Cable operated hose clamps are the NVP for this job. I went slow and cleaned things up in the engine bay while I worked. Also did the plugs, changed the thermostat and torque arm, and cleaned up the starter. Car runs much better now -- I think I had some vacuum leaks that were giving me minor driveability issues. Happy to have that done, but still have the transmission seal leak. Need to have an independent change that out -- looks like another beast of a job that's best done with a lift. I'm done turning wrenches for a while.

Punchline from my coolant tube replacement: I don't think it was coolant that killed the transmission seal. I think it just failed, or maybe it was from dirt/dust that got washed through the engine valley, but my pipes were not leaking. One of the tees was crusty, but I don't see how leaking tees would get coolant into the bellhousing.

My car came from New Mexico and appears to have been driven on a lot of dusty/muddy roads. Despite only 27000 miles when I bought it, there was a lot of dust/dirt in the engine bay and on the chassis. The engine valley had caked dust build up, but no evidence of coolant. The starter cleaned right up and looked like new -- no corrosion; just dusty. It's weird how the engine design drains the valley through the bellhousing -- seems like the engineers could have routed that around the bellhousing with minimal effort. Oh well.

In any case, looking forward to getting the transmission seal fixed and being done with car repairs for a while.

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Congrats on that repair. It will give you a piece of mind for a while. My ('06 CTTS) was definitely leaking from one of the Coolant Tees' (finished last month). I also did a bunch of the vacuum hoses while I was in there. I wonder if it would have been much easier to get at the upper bell housing bolts while you had everything off but I can understand not wanting to dive into a bigger project. I almost think it would be easier to lower the whole engine/tranny cradle a few inches then pull the tranny.  I lowered the rear of the cradle a couple of inches to get at the Coolant Tee's earlier.  Your right about the Cable operated hose clamp pliers, I ended up braking one and now my Toolbox has 3 different brands so I'll always be ready but may never use them again :).

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