Coolant leak, light flashing, fans running!

[nola911]

DJ, Cap #44701

Oh well, I thought I had it! Thanks anyway

[djomlas]

damn, although a good thing that you have 01 cap, too bad it wasnt a cheap $17 fix.
lets just wait what others say, hopefully someone else will have some insight

[nola911]

Ok, the repair shop (not Porsche) says it is a bad thermostat. I do not know enough about the cooling system to make a call, but the guy at the porsche parts desk seems to think otherwise. He cannot say what he thinks it is, but he says that thermostat wont go bad and if it does, it will not have my symptoms.

Anyone?

[MNBoxster]

Hi,

It could very well be a bad 'T'stat, or a leaking Coolant Reservoir, or bad Spring Clamps, or even a leaking Hose.

You'll need to do some investigating to zero-in on the cause.

A leaking Coolant Reservoir won't necessarily leak all the time. Small cracks may open up (expand) when the system is Hot and re-seal (contract) when the system is Cool.

Same thing with a failing Spring Clamp. System Hot (pressurized) the Clamp may allow Fluid/Steam to escape, while Cool (unpressurized), it seals OK. The same goes for leaky Hose(s).

The 'T'stat can be removed and checked by submurging it in Boiling Water. Check that it opens. For accuracy, use a Thermometer and see what temperature it opens at. But, for the 'T'stat, since you need to replace the Gasket, etc. when removing it for a check, on a car with some mileage, it's best to simply replace it altogether.

You can get a System Pressurizer: http://www.tooldiscounter.com/ItemDisplay.cfm?lookup=KDT3700 and pressurize the System Cold. Then you can check around the system while it is pressurized to look for Leaks. The Pressure Tester @ $90+ (possibly cheaper on eBay, Craiglist, etc.) may seem expensive at first, but it will allow you to do most Cooling System R&R yourself, eliminating expensive Shop Time - a worthwhile investment which you can also use on all your other cars as well. Hope this helps...

Happy Motoring!... Jim'99

[steve00s]

I went through several months of this schizophrenic coolant tank behavior. One day I would have a pool of coolant in the trunk and garage floor, a week would go by with things fine and then a pool again. The cracks in the tank were behind and below so you could not visually see them (of course). The hoses are very difficult to get at in the engine compartment as there just is not much room. You do not say what year your car is but if it is older than the tank might be the culprit as Porsche has had many problems with the earlier tanks.

[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.

[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