Coolant Still overflowing
 

I am stump I changed my expansion tank I also changed my cap I filled the system with the airlift and checked for leaks all was well. When the car gets up to temperature I see the fluid in the tank expand past the full mark and then leaks out. When the car cools off the coolant ends up being on the low side. The top of the tank is bone dry so why is it overflowing and from where?:mad:

My cap went bad and I replaced it with a new one (.04) and still had a overflow problem too. I did a lot of searching and read that the new caps are not as deep as the old ones. In a side by side comparison they looked the same to me. I tightened down the cap as much as I could by hand then when a tad further with channel locks. That fixed the issue. Hope this works for you.

Another way to check the system is with a pressure test.

Definitely sounds like an air pocket - try lifting the D ring on the expansion valve & leave open for 2-3 days (several heat cycles) and see if the coolant drops even further. Top up as required....

Wouldn't leaving the valve open invite air into the system? Shouldn't the valve release any pressure after it reaches a certain amount in the system?

I left the valve open for a couple of days and I am still having overflow problems. I can hear hissing coming from the relief valve even after I changed the o rings. I am at a loss. The cap is new the tank and valve are also new.

Aftermarket tank or Porsche?

It's an aftermarket but I checked it with airlift and it held the vacuum.

Try pressure testing it to around 18 PSIG and see what happens. I really dislike aftermarket tanks.

Didn't we just have a thread on aftermarket tank issues?

Yup, we did indeed, and the consensus was that they are not worth the money saved. Sometimes there really is no substitute.

^^^ ^^^
Especially when its such a pig to change out.....
Sometimes easy stuff to replace like the ignition switch, drop links, brake pads, fuel filter, etc, etc, you can get away with installing after market or alternative parts, but when the installation can take hours and/or the replacement parts are so important that the well being of the car can be compromised, the genuine Porsche approved bits are the best bet by far.

No Knock off tanks!!
 

I et th knock off tank is the issue - it was for me. If anyone does switch out their tank, I recommend using the vacuum tester on the tank before you install it just to be sure you have a good tank. I simply duct taped all of the hose ports, fit the airlift and applied a vacuum to make sure it held 20 psi vacuum.

After verifying a good tank, removing the recently installed leaky knock off tank and installing a verified good tank, I do not have any leaks, steam, or overflows.

At the end of the day, all is good but I wasted the money on the cheap tank and wasted 3 hours installing and removing it. Not worth it.

I know the knock off tanks are problematic but I did the vacuum test and it held the pressure fine. I even left it overnight and there was no leak. Could it have developed a leak only after the fluid became hot?

You are overlooking the fact that because of the way it is designed, it can hold vacuum, but not necessarily pressure.

I am still fighting a similar issue. Mine (original tank) holds vacuum, but not pressure. Very slow leakdown, when pressured to 19psi, it will lose about a pound after two hours. Still have not found where it is leaking. Can hear it after the car is hot, but can not find it. Have soaked it down with soapy water, still looking!

Go at it scientifically; buy some Uview coolant dye (get the correct type for your color coolant) and add it to the system. Run the car for a day to two, then park it in a dark garage and have a look around using a UV light (Uview also makes an inexpensive UV light flashlight). When you shine the UV light on the leak source, it will light up brightly, showing you exactly where it is leaking.

^ Porsche should use UV coolant dye in their coolants standard.
Park car in garage, turn off lights, look under car with UV light. All set, good night.

JFP, there is no fluid leak. I can hear air leaking at the coolant tank, and steam on the trunk lid. On my 4th 04 cap, too.

It's not steam, it's condensation, and if that's not a leak then what would you call it?

Where would you recomend getting a new Orem tank from? Who has the best deal?