Coolant leak, light flashing, fans running!

[MNBoxster]

Originally Posted by porsche986spyder

Sounds like it is a bad thermostat. That would explain why the car think's it is overheating and the fans kick on and the tank starts putting coolant back into the tank. A bad thermostat will send false readings to the cars CPU causing the codes to flash. I would start there.

Hi,

Just FYI... Not really, the 'T'stat (PN# 996.106.125.52) is simply a Valve controlled by a Thermal Spring. It is variable, and not merely an ON/OFF Valve, it meters the Coolant Flow to maintain optimal Engine Temperature.

When the Coolant is Cold, this Spring contracts, closing the Valve, and allowing the Coolant only to circulate through the Engine to build up to operating temperature more quickly.

When the Coolant is Hot, this Spring expands, opening the Valve, and allowing Coolant to circulate through the entire Cooling System Loop - Engine, Transmission (Tiptronic), Radiators, Coolant Reservoir, Heater Core.

It has no temperature sensing capability. It does not communicate with the DME in any way. This is done by the Coolant Temperature Sensor (PN# 996.606.405.01) located on the Left side of the Block by the #4 Cylinder. It is this sensor which supplies a signal to the DME, the Climate Control Unit, and the Dashboard Temperature Gauge.

When a 'T'stat fails, it can fail in either the Open or Closed position (or somewhere in-between. If it fails in the Open position, the Coolant will take a long time to come up to normal Operating Temp (if at all). If it fails in the Closed position, the Coolant in the Engine Block will quickly exceed normal Operating Temp as it is prevented from circulating to the Radiators and shedding it's Heat. Additionally, as the Coolant super-heats, the pressure in the system rises beyond spec which can lead to burst hoses, failed Seals and Gaskets, etc. resulting in a loss of Coolant from any number of sources.

Air in the system can prevent the proper operation of the 'T'stat if an Air Pocket finds it's way to the 'T'stat Housing, preventing the Coolant from reaching the Thermal Spring in the 'T'stat so it cannot be heated to operate the Valve and allow proper Coolant Flow. Hope this helps...

Happy Motoring!... Jim'99