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Matt, Engineer - BEng Hons
Category: Porsche
Satisfied Customers: 21611
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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Do the 2006, 2007 and 2008 Porsche Carrera 911 S models with

Customer Question

Do the 2006, 2007 and 2008 Porsche Carrera 911 S models with the 3.8 engines have the potential for IMS failure? I was told by a Service Manager that the S series with the 3.8 engines do not have the potential for IMS bearing failure.
Submitted: 1 year ago.
Category: Porsche
Customer: replied 1 year ago.
Does the 3.8 engine make a diference
Expert:  Matt replied 1 year ago.


The IMS bearing failure 'issue' can affect any water-cooled car (Boxster/Cayman/911) built from 1998 to 2009. From Aug 2009, the new DFI engines were introduced that were a clean-sheet design and don't have an intermediate shaft as part of their design.

In short, a sealed, ball race bearing is used to support the flywheel end of the intermediate shaft. Over time, the grease in the bearing can dry-out - often aided by excessive running temperatures as some of the bearings are a very tight fit in the casing due to production tolerances. As the bearing is sealed, oil from the engine can't normally enter the housing (although it sometimes does, with the effect that the bearings go on 'forever' ) and the bearing eventually breaks-up leading to catastrophic failure.

It appears that the main reason for the failures - the lack of lubrication as the bearing ages - has never been correctly addressed by Porsche. What Porsche has done is re-spec the bearing several times - single and double row bearings have been used, in several different load ratings. As all of the specified bearings have been nominally strong enough to carry the loads they have to bear (some many times the nominally required rating) but all have been of the same sealed design, the failure rates don't seem to be much different, irrespective of the bearing's spec / manufacture date of the engine.

A small number of engineering shops, have managed to redesign the bearing so it receives plenty of engine oil to both lubricate and cool it - this seems to have effected a cure. Such modified engines (that often have other modifications to the cooling system and cylinder bores) are greatly prized and seem to be more-or-less bullet-proof.

Bear in mind that the number of failures appears to only be a very small percentage of the total number of engines out there. The old adage that bad news gets discussed ad infinitum on forums, whilst good news never gets a mention, is probably very true where these failures are concerned.

Expert:  Matt replied 1 year ago.


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