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Coolant Loss on 997 C4 with 105k mls

  • 2006
  • 911 Carrera 4 Cabriolet
105 000
District of Columbia

I have a 2006 Carrera 4, 105,000 miles with a six speed manual.

I haven't had the car that long (have had several 996s prior), maybe two months and 6,000 miles.  I've done a lot of highway driving (several 400+ mile trips) at 75/80 mph since I have had it, and not sure it has been doing this the whole time, with no apparent coolant leak, but I keeping adding Porsche coolant and mixing it with the proper amount of water.  

I took it to the dealer who diagnosed the proplem as a bad expansion tank (even though it was replaced by the previous owner 7 months ago).  The stealership wanted $900 to fix it.   I took it to my regular mechanic (I didn't at first becuase I thought it was covered under a Porsche warranty since it had just been done, but the receipt shows it was done at an indy shop so no warranty).  My mechanic replaced it for $350 (yes, $550 cheaper), but there is no change in the coolant loss.

My mechanic changed the oil at the same time but he says it wasn't foul and noticed nothing unusual such as the oil mixing with coolant.  He did say it looked like there were hairline cracks in the expansion tank due to the other indy shop possibly overfilling it.

There is abslutely no smoke on start up either, either white or gray.  The only other thing I would mention is that when I opened the oil filler resevoir cap (not sure why I did this), there was a little bit of sludge inside near the cap, but I realize there is no oil circualting there... just strange since the oil was just changed.

Any thoughts?  I do have a Fidelity Powertrain warranty that was transfered to me, so in the unfortunate event it is something major, I should be able to have it covered I believe.

One more thing, if the water pump fails on this car, is it catastrophic?  I had an E39 BM5 M5; the water pump failed at exactly 100k miles and it cost $6,500 to fix.

FYI, the previous owner did commuting in this car and it has never been tracked.

Thank you for any assistance!  This is my daily driver so I need it fixed.



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