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I have just finished installation of a new water pump, thermostat and coolant reservoar cap (OEM Porsche parts) in my 996 C2 Targa/Tiptronic 2002 and is now ready to do a vacuum coolant fill mixed to factory specs.


When I read different instructions for manual filling/bleeding coolant system in a 996 equipped with Tiptronic gearbox they instruct:

” On Tiptronic vehicles, the pneumatically triggered coolant shutoff valve (flat-seat valve) must be opened for the bleeding process. The electric switch-over valve must be switched off for this purpose. Triggering can be performed with the Porsche System Tester 2 or by pulling out the Tiptronic control module fuse B-1 with the ignition switched off.” 


I can´t see this comment in any instruction for vacuum coolant fill. So, before i start the process my humble question is:

Is this comment also relevant to a vacuum coolant fill on a Tiptronic car?


If it is, shall the ignition be switched on during filling process?



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Here is how the tranmission cooling works...


Depending on the ATF and water temperature, the electric switch-over valve (2) is activated by the Tiptronic control unit (1) and allows a vacuum to enter the shut-off valve (3), The electric switch-over valve is activated at an ATF temperature > 85°C or water temperature >90°C. The switch-over valve is deactivated again if the ATF temperature falls below 75°C and the water temperature below 80°C.
1- Tiptronic control unit
2 - Electric switch-over valve
3 - Vacuum-controlled shut-off valve
4 - ATF-to-water heat exchanger


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Wow, that´s what I call a quick respons Loren! Thank you.

Just to be sure…my interpretation of your answer is:
The vacuum filling process also require to pull out the fuse B-1 as the electric switch-over valve shall be off so the shut-off valve can be open, as the water temperature surely would be below 80°C when filling. The ignition shall simultaneously be switched off during filling.
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