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04TT Coolant Pipe replace...what else while I'm in there?

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I have a new to me '04 TT w 89,000 miles. I spent a good bit of time with a dental mirror trying to see if the coolant pipes were replaced. I just can't see it. Tried for 40 min two seperate occasions. The service records I have on the car show that the starter was replaced and some vaccum lines replaced. July of 2009 @ Newport Auto Center Newport CA. But no sign of the plastic lines being replaced. The previous owner told me after I asked explicetly that they were changed. I can not understand why if they replaced the starter they would not have replaced the lines. At this point I can't tell if they were but does not look like it.

If they are not replaced then I have to have them done right now. No sense ruining another starter and transmission seals or be stranded. The question is this:

What else needs to be replaced while the intake is off and we are in there anyway?

Would appreciate a comprehensive detail as to what should just get done here.


Also this one has trailer hitch. Back at the receiver there is a square plate with four screws. Is the trailer harness socket under that plate? Can I plug a 7 pin plug into it if I remove the square plate? This one has a cd changer back there but service records show that installed update trailer hitch system control. Not sure what that actually means.

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Hi Nylon:

Congratulations on your Cayenne purchase and welcome to Renntech. Be sure to search these forums and you can read up on all the issues and items to cover if and when you replace your coolant pipes -- what else to do while you're in there, etc. (You can also read about some other methods to check exactly what pipes you have installed.)

And for your hitch -- if you become a contributing member you can review the DIY section which has a lot of hitch details, pictures and instructions.

Happy Holidays!

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Thx for the response,

I have searched through the board and found tidbits. The concern is that I don't want to miss anything while in the guts. I have not found a singular thread that compiles the items that should be addressed while under the intake. The plastic to aluminum pipes are the main objective. I have noticed references to other plastics, fitings and T's to freshen up. A group contribution to a single page of "fix these while in there" is what would be ideal.

I am in a frenzy getting things ironed out with this SUV. So many things to resolve quickly. I am so happy to find an invaluable board like this with this kind of information. Being 200 miles from closest dealer service, I will have to do much of the "doable" work. I will certainly become a contributing member. And will research what that means and how it works and what I need to do.


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Hi John! My mechanic suggested doing the water pump while you are in there. I did not because it was already a $2200 job and I knew it had a few more miles. My water pump lasted 128,000 and I'm still nursing it with an occasional splash of coolant until after the holidays when I will replace it. My coolant pipes were replaced around 60,000mi or so. Hope this helps!

Tim in Ft Worth

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Thx Tim,

Records show water pump replaced at 77,000. What will these Cayennes go to? Can I get 200,000 with out huge failures? Figure control arms axle shafts and joints. Engines and transmissions go that far?


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Common issues include front control arm bushings, cardan shaft centre bearing support, water pumps, coolant pipes, ignition coils.

Transmission is solid except for the hydraulic solenoid valve body unit.

Change the valve body unit when transmission starts to do hard shifts.

Recommend changing transmission and drivetrain fluids at half life to extend life of components.

The M48.00 engine had some issues with cylinder scoring and piston slap due to no piston cooling oil jets being fitted.

The turbo M48.50 variant however has the ccoling jets and has proven to be bullet proof.

Edited by bigbuzuki
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Thx again,

I am most interested in what need to be dones while changing plastic pipes to aluminum. I had seen somewhere a mention a while back that there were also two plastic "T"s and some other things that go out as well. Anyone know what they are and where they are? I remember one of those Ts were mentioned to be very difficult I think.


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  • Admin

Thx again,

I am most interested in what need to be dones while changing plastic pipes to aluminum. I had seen somewhere a mention a while back that there were also two plastic "T"s and some other things that go out as well. Anyone know what they are and where they are? I remember one of those Ts were mentioned to be very difficult I think.


There is a written DIY in the DIY Tutorials section here.

And Contributing Members can view the Porsche TSB on this.

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  • 3 weeks later...

Unless you want to change the plugs while you're doing the coolant pipes there isn't much else to do since the starter has already been replaced. Of course, you may be replacing several broken plastic vent tubes, an unfortunate result of doing the coolant pipe job. Been there, done that.

I might have the plugs on hand in case you dismantle the intake and find the pipes already replaced. At least all the work won't be in vain, albeit a little overkill.

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  • 1 year later...

Guy and Gals,


Just reread my post and want to thank all of you for the information.  I seemed to be singular in mind but as I re read I notice more good advice that came to me that I didn't properly acknowledge at the time...so Thanks Again!  So far I am finding an older Cayenne to be a great car / truck ... car to me since I have two 3/4 ton suburbans.  Once they are demystified a bit and re discover that they are still trucks and car machines underneath it all.  So much goodness with incredible weakness.  ie plastic coolant tubes/ Ts in Cayenne.  IMS bearing in the 99-04 911's and a worse ims bearing in 05 + 911s.  Engine wrecking faults, leave you stranded and or very expensive repairs.  Discovering the 911 issues as I am looking to buy an 03-05 911C4.  How can a carmaker make such good vehicles yet make such colossal engineering blunders?

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  • 2 weeks later...

I would take the time and do the two coolant T's on the back of the motor, coolant temp sensors, reservoir and cap, and the thermostat.  That would cover everything and should get you to 200K miles without issue.  The parts are all relatively cheap - about 450 bucks for all of it.  I call that relatively cheap to know that I shouldn't need to touch the coolant system for a good long while.  


Coolant Sensor


Water Pump


Water Pump Gasket


Coolant Reservoir


Res Cap




Thermo Gasket


Thermo Rubber Seal


2 T-hoses


Intake Gasket


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