NHTSA was investigating for "rapid coolant loss caused by coolant pipe-fitting failure, allegedly resulting in vehicle disablement and/or loss of vehicle control due to reduced traction for the affected vehicle or following traffic," according to the regulators website. "Most of the leak complaints did not appear to involve complete separation of the fittings and many were detected when the vehicle was parked," said NHTSA's statement.
There were 63 complaints and 336 warranty claims, although the investigation was initiated after ten complaints from customers. There have been no reports of crashes or injuries attributed to rapid coolant loss.
"A safety-related defect has not been identified at this time and further use of agency resources does not appear to be warranted. Accordingly, this investigation is closed. The agency will monitor this issue and reserves the right to take further action if warranted by the circumstances," NHTSA said.
Scroll down for the more technical explanation in NHTSA's official bulletin.
On April 26, 2013, the Office of Defects Investigation (ODI) opened PE13-009 to investigate 10 complaints alleging incidents of sudden coolant loss while traveling on public roadways in certain model year (MY) 2001 through 2007 Porsche 911 vehicles. The complaints alleged that pipe ends joined by epoxy to certain cooling system components may fail suddenly and separate, resulting in large volumes of coolant leakage. The investigation was opened to assess evidence of a design or manufacturing defect in the coolant pipe fittings and any related safety consequences. In response to ODI?s Information Request letter, Porsche identified a manufacturing quality issue with the supplier?s application of adhesive to coolant pipe fittings that resulted in elevated failure rates in approximately 6,800 early production 997 generation vehicles (MY 2007 and early MY 2008). ODI?s analysis of field data showed that the age-adjusted failure rate for these vehicles was approximately six times greater than MY 2001 through 2005 996 generation vehicles and MY 2008 through 2011 997 generation vehicles built after a process improvement for adhesive application was implemented by the supplier. Most of the leak complaints reviewed by ODI did not appear to involve complete separation of the fittings and many were detected when the vehicle was parked. There were no crashes or injuries reported to be related to the alleged defect in any of the subject vehicles. ODI identified two allegations that coolant leakage resulted in loss of control incidents, but neither involved vehicles affected by the assembly process quality issue. A third loss of control allegation involving a vehicle built during the period affected by the supplier process concern is not counted since ODI was unable to contact the owner to confirm the incident. See the full closing resume in the document file for PE13-009 for additional information about the subject cooling system and ODI?s analysis of field data related to the alleged defect. A safety-related defect has not been identified at this time and further use of agency resources does not appear to be warranted. Accordingly, this investigation is closed. The closing of this investigation does not constitute a finding by NHTSA that a safety-related defect does not exist. The agency will monitor this issue and reserves the right to take further action if warranted by the circumstances.