Today we know that the IMS (Intermediate Shaft Bearing) has been a major cause of concern for owners of 986/987 Boxster and 996/997 Carreras. It is generally accepted that far fewer problems are being experienced with the M97 engine, but that said, there have been IMS bearing failures in M97 engines also. Unfortunately, the IMS bearing in the later M97 engines cannot be easily replaced like in the M96; the later M97 requires complete disassembly of the engine for IMS replacement. One of the main concerns relative to these later M97 engines is how the factory’s larger IMS bearing will hold up over the long term when the miles driven get well beyond that of the 100,000 mile mark. The potential for serious engine issues is not something new for those of us that have owned 911’s over the years. For those who have, it is likely you are aware that there have been multiple problem areas with these engines. Oil leaks for all years. The cylinder head studs in the 1975-1989 911’s. The pre 1984 911 mechanical chain tensioner failures, this could cause catastrophic engine damage. A 911 equipped with CIS fuel injection could experience an air-box explosion with the possibility of engine damage. The 993 is affected with premature valve guide wear causing excessive oil consumption resulting in carbon buildup in the secondary air injection (SAI) ports; this could cause a failure to pass the mandatory bi-annual emissions inspection. Relative to these and other potential failures, Porsche, the aftermarket parts business and or knowledgeable technicians have come up with fixes, upgrades or maintenance procedures that can correct these problems or mitigate the likelihood of the problem ever happening.
The same holds true today with respect to the IMS problems. The high quality, composite IMS bearing retrofit available from LN Engineering is a great example. The IMS Guardian from Flat-6 Innovations also provides a means to monitor metal debris in the oil and warn of an impending engine failure. Installing one of these products in your car is likely the best thing you can do for it. It is also important to consider a maintenance schedule that is beneficial for your engine, not necessarily what the manufacturer recommends in that given model year. A general health plan prescription for the IMS bearing might look something like the following:
- Change the engine oil and filter every 3k to 5k miles or once per year, even though you are running synthetic lubricants.
- Utilize boutique type synthetic engine lubricants that have elevated levels of ZDDP (Zinc Dialkyldithiophosphate) additives with a minimum of 1250 PPM.
- Cut the engine oil filter open and inspect it for any metal, plastic (brown) and or rubber (black) debris at every engine oil change.
- If higher quantities of metal debris are found in the oil filter, consult a Porsche Technician, then send a 3 to 4 ounce sample of the used engine oil to a lab for analysis.
- If purchasing a pre-owned Porsche with the M96 or M97 engine, insist on a thorough PPI (Pre-Purchase Inspection) and make sure to review the written service records of the car. Be certain that the service intervals were reasonable. It’s a good idea to inspect the engine oil filter (as noted above) and camshaft deviation values during the PPI.
- When the engine is at full operating temperature, drive with the RPM’s elevated, if possible accelerate to or near engine redline once or more times per driving cycle under full throttle. Only upshift when above 3,000 RPM.
- Install LN Engineering’s magnetic engine drain plug and spin on oil filter which has improved filtration capability.
- Install LN Engineering’s composite IMS retrofit bearing as soon as possible. If the IMS bearing replacement cannot be done in a timely manner, consider the installation of Flat-6 Innovation’s “IMS Guardian kit”. Specific to the later M97 engines, due to the difficulty and cost involved in replacing the IMS bearing, we suggest installing the IMS Guardian to monitor the engine in case an IMS failure develops.
The risk and consequences associated with an IMS bearing failure are serious. Taking these extra steps for service, maintenance and replacement of the IMS bearing or installation of the IMS Guardian will go a long way towards insuring the health of your M96 or M97 engine.
Tony Callas & Tom Prine