Coolant Leak

[iamtheari]

I know that the topic has been beaten to death, but I am not finding a lot of information that really helps. My 2004 Cayenne Turbo has a moderate coolant leak. From the high mark in the expansion reservoir to the low coolant warning takes about a week of daily driving, but particularly when it is close to full the leak becomes very visible under the car.

The coolant drips down almost entirely on the passenger side of the vehicle. the bulk of the dripping happens about even with the rear of the tire and about 10 inches toward the middle of the car from the inside edge of the tire. Some of it drips on the steering boot and some drips on the axle boot. Most of it drips just behind the steering boot.

There appears to be dampness running down from the expansion reservoir but I cannot localize exactly from where and it is not flowing down in sufficient quantities when I look at it to match the amount of coolant dripping below. Of course, it could leak out when I'm driving down the road, catch in the various pieces of tinware around the engine, and then flow out from there when I'm stopped to look at it.

It only leaks when the car has been running, not when it is sitting cold. I do not have a way to pressurize the system other than by running the engine and there are no auto parts stores within a reasonable distance from which I can borrow a pressure testing tool. (O'Reilly would lend me one but only for 3 days, and there is no way I can get there more than once a week given the distance.) I'd prefer not to buy a $200 tool that I will only use once.

Lots of reading since I noticed the leak has led to the following possible sources:

• Expansion Tank Cap: ruled out because there is so much coolant coming down that it would be visible at the cap, and none is
• Water Pump: unlikely because of the drip coming down at the rear of the engine, but I have a replacement in hand and will do that anyhow as the car has 130k miles
• Expansion Tank: this seems most likely and I have one en route to arrive on Monday
• Coolant Pipes: mine have supposedly been upgraded to the metal ones already, but I will verify that when I replace the purge valve to avoid rough starts after filling the gas tank in hot weather; unlikely as source of this leak because of the amount of the leak, which I have read should either be a lot less with a cooked coolant smell or much, much more and a non-driveable car
• Coolant 'T' at rear of engine: also unlikely for same reason as coolant pipes, but if the leak persists after the pump and tank are replaced I will take a closer look also when I get around to the purge valve job

Did I miss any that I should take a look at? The 'T' seems almost impossible to get an eye on even with the intake removed and that will have to wait until I get to the purge valve job. Right now that's low priority since it only affects the first attempt to start after filling with gas, and seems only to have troubles when it's hot which is no longer much of a risk for the next few months. Better tires and the coolant leak are much higher priority!

I also plan to drain the coolant as part of this task. There seem to be differing opinions on how to re-fill it. Some claim that you have to vacuum-fill the system. Others claim that the engine is self-bleeding so you can simply fill the tank, start the car, drive, and top it up when it's cool. Does anyone have direct experience to say for sure what's required?

Thanks for anyone's input and experience on this. I love the car so far, just have to work out all the quirks.

[914-6Porsche]

I have an 04 T and the T connection was not changed with the pipes and one day it puked all over the place but the beak could be smaller. Your pipes would have failed long before the 130k miles.

[iamtheari]

It looks like I might be one of the lucky ones. I replaced the coolant expansion tank and the moderate leak I had is no longer happening. This was a relatively easy job assuming you have the right tools and do not drop too many of them into the myriad nooks and crannies in and around the Cayenne V8 engine.

[914-6Porsche]

Glad to know what you found. If I have another leak, I'll check it first. Thanks!