Porsche IMS Bearing - Explained

Porsche 911’s and Boxster’s are a rare mix of performance, practicality and quality German engineering. The brand is revered as one of the top quality automotive manufacturers and for that reason, Porsche is loved around the world. Porsche vehicles also maintain incredible resale value compared to their competitors, even when their mileage racks up to 2-3 times that of their direct competitors. With regular maintenance by a Porsche specialist, it is not uncommon to see a modern water-cooled daily-driven 911 on the market with 150,000km or more.

Like all vehicles, 911’s and Boxster’s have their unique maintenance areas to pay close attention to; one of the common areas for Porsche being the Intermediate Shaft Bearing, commonly referred to as the “IMS” bearing.

As Porsche owners, most of us have heard about the IMS bearing, but what is it and why do we need to know what it does? Basically it’s a bearing at the back of the engine that requires removal of the transmission to access. There are several “while you’re in there, let’s replace more” parts, but we don’t want to get into all of them. The main one’s to mention are that a clutch replacement and Rear Main Seal are often combined with the IMS retrofit installation, at minimal additional labour cost.

Most commonly the IMS issue applies to most 1999 to 2005.5 Porsche 911’s and Boxsters with the M96 engine and early M97 engine. Turbo owners need not apply. You don’t have this issue in your cars.

Now back to the IMS bearing. The purpose of the intermediate shaft is to drive the camshafts indirectly off the crankshaft. By using an intermediate shaft, the speed of the chains are reduced, which is better for chain life and the longevity of all components involved. This basic design was used throughout the entire lifespan of the aircooled six-cylinder Mezger Porsche engine used through 1998. The inclusion of an intermediate shaft, which drives the camshafts indirectly off the crankshaft, has become a mainstay of the horizontally-opposed flat 6 engine utilized by Porsche.

The earliest IMS design incorporated a dual-row ball bearing used up until 1999 (and included some 2000 and 2001 Boxster models). Starting in late 1999 Porsche began phasing out the dual row bearing and went to a smaller single row bearing design, with significantly less load capacity. It is highly recommend that all Porsche 911’s from 1999 to 2005.5 have the factory single row bearing replaced with our upgraded IMS bearing.
Starting with the 2006 model year, the design was again revised to use a much larger single row bearing with the same load capacity of the early dual-row IMS bearings.  However, for 2006 to 2008 911 models, the existing IMS bearing does not require replacement, but it may require removal of the factory “grease seal”. This helps the bearing to receive adequate lubrication to ensure long life. Removal of the grease seal requires removal of the transmission and is often done at time of clutch replacement and rear main seal.

In addition to IMS bearing failures, the intermediate shaft can suffer other failures including but not limited to slippage of drive sprockets which can lead to valve timing related failures.
When an IMS failure occurs, the intermediate shaft is likely damaged beyond the point of being serviceable. Moreover, debris from the failure contaminates the entire engine, requiring a complete teardown and rebuild to recover from such a failure. In worst-case scenarios, the camshaft timing can also be thrown off, causing valve to piston contact, and in some cases, even lead to a failure that requires replacement of the entire engine.
What does this mean for you? We don’t want you to even come close to the scenarios listed above, which is why it is extremely important to ensure your Porsche is taken care of by a Porsche expert. Riegel Tuning specializes in IMS bearing inspections and servicing, so you don’t have to worry about an engine failure or even the lesser IMS failure. We take the time to get to know your Porsche and know our stuff when it comes to water-cooled Porsche models. For all your maintenance and technical diagnosis needs, be sure to contact Riegel Tuning’s service department for true peace of mind.

Book your Porsche in with Riegel Tuning today for a complimentary Expert Inspection

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