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Old 06-18-2007, 06:37 PM   #1
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Coolant leak, light flashing, fans running!

Ok guys, if you have any advice or suggestions let them fly. It started 2 months ago with a coolant leak behind the right rear tire. The tank never drained past the full level. I figured it was overfilled and some came out the overflow (if there is such a thing). There was no moisture in the trunk and no puddles under the carpet. The tank itself is not damaged.

Now, it has been 2 months and maybe 100 miles since then without incident and absolutely no puddles in the garage... until this weekend. The whole tank emptied out similar to before behind the rear tire. Today, I put two cups of water in it expecting it to rush out a bad hose, but it did not leak. The water was not even half full in the tank. I started the car and let it sit for 15 minutes. It ran fine for a while, then the tank started filling with coolant from somewhere else in the system. As it did this, it overflowed itself and started leaking and the thermostat started to near the third temp line (over 180).

I turned it off and summoned the Bently guide and 986 forum search for ideas. Having struck out, I went back to it. Now, with the tank miraculously at the typical fill level, I restarted the car and took it out of the garage thinking it might be the hot single car garage that was making it hot. I drove around the block. As soon as I made the first turn, the red light on the right of the temp started flashing and the fans started running. It ran a little hotter than usual (near the third line), but not getting near the top temp. By the time I made it back home, the fan was running harder.

Am I correct in asuming the light flashes if it is too hot OR if the radiator has no fluids?

I read of leaves or debris sometimes block radiator flow, but my garage queen has no such debris.

Any help is deeply appreciated. I want to avoid the 300 dollar tow fee to porsche if it is something minor that I (or local german repair shop) can handle.

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Old 06-18-2007, 06:48 PM   #2
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open the trunk and see if you have a blue cap that ends in 01, if you have one that ends in 00 theres your problem.
happened to me, emptied out the whole tank behind the tire while driving
btw, te car is only around $17
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Old 06-18-2007, 07:32 PM   #3
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DJ, Cap #44701

Oh well, I thought I had it! Thanks anyway
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Old 06-18-2007, 08:23 PM   #4
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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
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Old 06-20-2007, 05:17 AM   #5
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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?
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Old 06-20-2007, 07:14 AM   #6
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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

Last edited by MNBoxster; 06-20-2007 at 07:32 AM.
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Old 06-20-2007, 08:37 AM   #7
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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.
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Old 06-20-2007, 09:06 AM   #8
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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.
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Old 06-20-2007, 12:43 PM   #9
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I had leaking problem that turned into overheating problem in a 03S. porsche towed it and tested everything and finally said it was the coolng system cap not allowing system to pressurize properly. Air in system, water pump cavitating? No problems since thay gave me a new cap, 10 months.
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Old 06-20-2007, 06:35 PM   #10
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Update:

I ordered the thermostat and it will be in tommorow. The shop pressure tested the coolant system and they said everything was tight. Both porsche and this indy shop agree that air could have gotten in the system, and that the thermostat is the first thing to look at. For my own peace of mind, I am replacing the tank cap and the seals while it is being ripped apart.

I was able to get the coolant to leak while I had the carpet pulled off the trunk and it seemed the tank was sealed because none entered the trunk.

Mere trivia: for those who have never bought coolant from porsche, it costs 55 dollars a gallon
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Old 06-20-2007, 07:09 PM   #11
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I forgot to add, the car is a 2000 model.

Thank you all very much for the help
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Old 06-20-2007, 07:36 PM   #12
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there is cheaper coolant to get, go look at the DIY section , i flushed the system, and the guide is there, as well as what coolant to use that is also approved, and will save you a LOT of money
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Old 06-21-2007, 09:02 AM   #13
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Quote:
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
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Old 06-21-2007, 11:08 AM   #14
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Jim, incredible! It seems like my shop is on the right track then, they said to check the rest of the system, the thermostat needed to be replaced and then they will troubleshoot from there on.

Thanks again guys,

max
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Old 06-21-2007, 11:53 AM   #15
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i agree with jim for the most part. if you weren't overheating before the leak, then your problem is almost certainly air in the system. not sure how to purge it on a boxster. before replacing the t'stat i'd fill/purge the system, and see where the leak is coming from. while it might be leaking from over pressurization, if you weren't having an overheating prob prior to the leak, it's more likely just a heat-responsive leak in the tank/hose/etc.
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Old 06-21-2007, 02:09 PM   #16
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Hey nola,

For work, do you take your car to benson or greff?
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Old 06-21-2007, 08:26 PM   #17
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actually, i should upgrade my info. just moved to birmingham and JUST got the car yesterday, so i don't go to either. but benson's a punk.

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