Porsche’s IMS Bearing-Identifying The Problem

Porsche IMS Bearing Kit 2

Porsche’s IMS Bearing-Identifying The Problem

So, chances are you’re here because you have a water-cooled Porsche flat 6 and are worried about your IMS bearing. The Porsche IMS Bearing is a scary subject for a lot of Porsche owners; and for good reason, as it can cause catastrophic damage to a very expensive engine. In fact, used and rebuilt engines can be so costly, it can potentially put you “underwater” on the value of the vehicle. The good news is that the aftermarket has identified the problem and has a plethora of solutions in order to rectify this potentially devastating design flaw. Having worked on Porsches for a number of years, we have personally experienced and corrected many problematic IMS bearings with the M96 and M97 engines.

The fact of the matter is that nearly all Porsche 911 and Boxsters from 1997 to 2008 using the M96 and M97 engines, will ultimately fail due to this design flaw. Over the years, Porsche attempted to rectify the problem by changing the bearing’s size and width. Each iteration, however, yielded the same eventual failure. Changing the bearing size, width, or lubrication does not solve the problem, but rather changing the method or type of bearing corrects the problem. This is not a scare tactic, but rather a knowledge that can be used to make a beneficial decision. Delaying the fix potentially exposes you to a catastrophic motor failure that can cost upwards of $15,000.

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Maybe you’re here because you know that the IMS bearing is a problem, but don’t know who to trust, let alone what actually goes wrong. Let’s start off with a simple description of the intermediate shaft and bearing. The intermediate shaft is the link that drives the camshafts via a chain from the crankshaft. It has been a staple on air-cooled six-cylinder Mezger engines used through 1998, however, didn’t reach its notoriety for failure until the water-cooled M96 and M97 engines. This means that from the start of its production in 1998 stretching all the way through 2007, water-cooled flat-six engines and its derivatives are prone to failure of the ball-bearing found in the intermediate shaft. ((More on the issues here.))


To give you the short version, when you hear the term “engine bearing”, this is typically referring to an oil supplied bearing inside the motor. These bearings are forced lubrication by the engine oil pump. The oil removes friction and heat from the bearing surface as it passed through the oil filter and oil cooling systems. Well, the engineers at Porsche decided that the bearing for the Intermediate shaft would consist of a sealed ball bearing similar to a wheel bearing. According to them, it didn’t need supplied oil. Even better; it should last for the life of the engine…

The IMS bearing design was revised by Porsche three separate times between 98-08. For the years between 1999 and some 2000 models, the initial design were ball-bearings lined up in a dual-row configuration. However, due to a cost-cutting design change in later 2000, a single row ball-bearing was used with a significantly reduced load capacity. By 2002, all non-turbo engines switched to this smaller, lower capacity single-row bearing design. Fast forward to 2006, the design was again revised to use a much larger and more robust single row bearing with a similar load rating of the early dual-row bearings. However, this third revision of the intermediate shaft bearing design is not serviceable without engine disassembly. In all revisions, a sealed ball-bearing style was used, rather than allowing for engine oil located in the sump to lubricate and cool the ball-bearing.


Porsche IMS Bearing 1

Ball bearings consist of an enclosed unit housing small steel balls and a lubricant that is permanently sealed inside. As previously stated, the lubricant and steel balls inside an IMS Bearing were intended to last for the entirety of the engines life. While this was the intent of the design, the IMS bearing proved that over time, it would deteriorate. The grease would slowly “seep” and begin to escape from the bearing, causing rapid metal on metal friction from the steel balls riding on the inner race of the bearing. Eventually, the IMS Bearing’s outer race begins to make contact with the IMS flange. ball-bearing bearing both the Intermediate Shaft and the flange itself. From here the metal begins to shred and falls into the engine oil, where it is picked up by the oil pump and forced into the oil supplied bearings and cylinder walls. The result from the circulated metal debris is increased friction on critical engine components while components collide resulting in metal particles traveling throughout the engine and ultimately, valve-train timing becomes compromised. This cascade effect of failures can lead to a costly engine rebuild or in some cases, replacement.

When an IMS failure occurs or more specifically the ball-bearing support fails, the intermediate shaft is damaged beyond the point of being serviceable. Even worse, debris from the failure contaminates the entire engine, requiring a complete teardown and rebuild in order to fully recover from such a failure. In a worst-case scenario, 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 engine. In that case, the engine will not be accepted as a core, requiring the purchase of another core or to pay an ever-increasing core charge from Porsche on top of the cost for the replacement engine. Aside from the proactive approach of replacing the IMS bearing prior to such a failure, prevention, and early detection are some of the steps that can be taken to try to minimize the risk of a costly engine failure.


When will my IMS bearing fail?

There is a lot of debate around this issue. Common sense would dictate that the older the vehicle is and the higher the mileage, the more susceptible it would be to bearing failure. This; however, does not appear to be the case. It seems that bearing failure is just as, if not more likely, to occur on the pristine 20,000-mile collector car as it is the 120,000-mile race beater. There is limited information available but the overall consensus is that lower mileage vehicles with infrequent oil changes or driven in low speed/engine rpm areas, will more commonly suffer a failure than those cars that are driven hard and well-maintained.

Some theories point to the fact that at low engine rpm, the IMS bearing is loaded to the smaller, inner race. During high RPM engine speeds, centrifugal forces shift the load to the outer race of the bearing. This race is slightly more robust and thus can offload the wear more effectively. This is just a theory, but what we can take away from it is the faster you spin the IMS bearing, the less it will wear and the longer it will last. Driving your Porsche more regularly and keeping it in lower gears in order to keep RPM above 2500-3000 is actually a good methodology to follow. This can improve the life of the IMS bearing, until a time where you can have the repair performed.

How can you tell that your Intermediate shaft is going bad?

The first thing to go bad on the bearing is the seal. The original bearing seals were only rated for a maximum temp of 250F. Like any soft rubber silicone based seals, over time, they become hard and begin to break down. This allows engine oil to “wash” the grease out of the bearing. The centrifugal forces then spin away the rest once the seal fully deteriorates. It is at this point that you can begin to find rubber, plastic and metal debris in the oil filter showing initial signs of failure. If you purchase a magnetic drain plug, this will attract the ferrous metallic metals to the plug, and gives an indication of how the deterioration of the bearing is progressing. Magnetic debris from the intermediate shaft bearing can be identified easily, appearing small, like silver glitter. Larger debris than this is indicative of a complete failure.

removing the IMS bearing cap

The next sign of Potential IMS failure is a large oil leak from between the engine and transmission. This is an indicator that the center bearing support stud has failed during operation, resulting in excess oil coming from its location. If this is seen, it is imperative that the vehicle no longer have the engine started or ran. This is what you’ll see right before catastrophic engine damage, but if it has come to this point, it may already be too late.

I just bought my car and don’t know if it’s been done, what can I do in the meantime?

If you know you haven’t had your IMS replaced, you should be doing more frequent oil changes with a high quality, fully synthetic oil, such as the one we use here at Fluid MotorUnion FMU Oil Change. For Porsches where IMS service history is in question, perform the oil change at intervals of every 3,000 miles. During these services, the oil filter should be cut apart and inspected for debris. For monitoring, we recommend an aftermarket magnetic oil drain plug such as Magnetic Drain Plug is good, but won’t help a new car owner who just bought a vehicle with freshly changed oil. Adhering to shorter oil change intervals may assist owners with identifying a failure in its early stages but later models using the single row bearing can fail with little warning. Ultimately, if you don’t know for sure, get it done sooner than later

Replacing the IMS bearing

Porsche did not provide a recommended service interval for these bearings nor provisions for their replacement from the factory. Recently, however, the aftermarket stepped up in a huge way, with a variety of companies offering replacements and “solutions”. Thankfully, the IMS bearing is now serviceable with relatively routine, but labor intensive, preventative maintenance for model years 1997 through 2005 Porsche water-cooled engines, so these costly repairs can be averted.

M97 IMS Bearing (non-removable)

This M97 IMS bearing is non-removable due to the case opening being too small.

However for those who own 2006-2008 Porsche’s, the intermediate shafts that cannot have their bearings replaced without a costly, full engine teardown. What is now recommended is to remove the grease seal from the existing bearing and allow engine oil to freely lubricate the bearing. Because it is still a labor-intensive job to gain access, we suggest only when doing another procedure like a clutch, flywheel, or rear main seal replacement.

M97 non removable IMS Bearing with grease seal removed

This shows the M97 with the grease seal removed for better lubrication.

Now please keep in mind that an intermediate shaft bearing repair procedure should NEVER be carried out if the original bearing has started to fail. If the bearing needs to be cut out of the IMS bearing shaft to separate it, the original bearing has reached the point of failure, and it is too late. If the damage hasn’t spread to other components, at the very least, the engine will have to be fully disassembled and intermediate shaft replaced with new.

For earlier engines that don’t require a full tear down, typical replacement of the IMS bearing takes 10+ hours and again, is best to done while replacing the clutch assembly or any other service that requires transmission removal.

With the transmission removed, we put the engine to TDC and insert the locking tool. We then remove the cam covers to attach the Porsche specific tool to lock the camshafts into place. This avoids the chance of the camshaft to crankshaft timing jumping accidentally while working with the intermediate shafts bearing.

Porsche IMS Bearing Kit special Tool 7

We then remove the engine oil and both banks chain tensioners.
With this stuff out of the way we now have access to the IMS bearing. The flange is separated from the inner IMS bearing race and pulled out with special bearing puller tools. With the bearing removed, the surfaces are cleaned and prepped. The newly upgraded bearing is cautiously pressed into position in with another special tool, and then the flange cap is carefully placed onto it.

Porsche IMS Bearing Kit 1

Now with there being so many IMS repair options currently available, we usually end up using whatever IMS bearing the customer requests. If you are asking our professional opinion, we recommend the EPS Eternal IMS Fix. What really separates their design from the competition, is the ingenious way they get fresh oil to cycle through their bearing design. Using a precise, strategically placed hole that is added to the front cover of the IMS. Removing the Oil Pump and replacing the factory 8MM Allen drive with a slotted 8MM drive will provide a governed oil passage from the pressure side of the oil pump into and through the IMS. This pressurized oil will flow through the intermediate shaft and into the IMS bearing. This maintains a constant, fresh oil flow to the IMS bearing in a simple, cost-effective method. Removing the oil pump cover and gears is obviously required, however, the extra labor is a small price to pay for an IMS bearing with a constant supply of fresh oil!

Replacing the IMS bearing is one of the most important things that you can do to protect the value of your Porsche. With water-cooled engine cores becoming rarer and used engines becoming increasingly expensive, the damage from a failed IMS bearing could have devastating financial repercussions. If you have questions regarding your IMS bearing, give the experts at Fluid MotorUnion a call. We have the knowledge and experience to make sure you know the potential issues associated with Intermediate shaft failure, as well as the ways to ensure you keep the value in your vehicle investment. Our new location right in front of Iron Gate Motor Condos in Naperville and is equipped to handle all of your Porsches needs.

Iron Gate Motor Condos Cartoberfest Motor Plaza

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