Case Studies

Porsche IMS Bearing: The Facts Made Simple – How We Can Help!


The Porsche IMS Bearing: The Facts Made Simple
Credits: LN Engineering and Atlantic Motorcar Service

As a late model Porsche owner, you have likely heard the acronym “IMS” but every time you’ve searched on the internet, you’ve come away with more questions than answers.

Our Background
After 35 years of European, and specifically Porsche service, we know a thing or two about this problem. We’ve spent considerable time in the workshop speaking with our technicians and distilling the very best factual information about IMS bearings, their importance and what exactly does go wrong. Below you’ll find the most commonly asked questions regarding the IMS bearing along with a simple easy to understand explanation of the issues!

We hope this will help you have a better overall grasp of what exactly the IMS bearing is, as well as what goes wrong and what is involved to make sure it doesn’t happen to you and your Porsche

What Is An IMS bearing?
IMS stands for ‘Intermediate Shaft’, and the IMS bearing supports the intermediate shaft, on the flywheel end of the motor (See below).

The purpose of the intermediate shaft is to drive the camshafts indirectly off the crankshaft. By using an intermediate shaft, the speeds of the chains are reduced, which is better for the chain life. This basic design was used through the entire lifespan of aircooled six-cylinder Mezger engines used through to 1998. The inclusion of an intermediate shaft which drives the camshafts indirectly off the crankshaft has been a mainstay of the horizontally-opposed flat 6 engine utilized by Porsche.

The same design has been retained with the water-cooled Turbo, GT2 and GT3 models as their engines are based off the same 964 engine case with the same internals as the earlier aircooled engines. Although these engines use an intermediate shaft, with a bearing, they have a fundamentally different design, and are not subject to the same type of failure as the M96 engine.

What Porsche models are prone to IMS failure and would benefit from an IMS upgrade.
– All 996 models (not including: GT and Turbo models)
– All 986 Boxster models.
– 987 Cayman & Boxster models up to engine number 61504715
– 997 3.6 liter with M96/05 up to engine number 6950745

So What Actually Goes Wrong?
There are so many reasons for bearing failure, and usually each failure is due to a combination of factors, not just a single cause.

Spalling, one of the most common of failures, occurs as a result of normal fatigue where the bearing has reached the end of its normal lifespan but this is the most common cause of IMS failure.

Spalling detected in bearings can generally be attributed to a number of factors; a common cause of bearing failure is due to high load and lack of lubrication to the IMS bearing, causing continuous over heating. Dirty, or low quality engine oils will contribute to this failure, as will a low quality filter, improper warm up, or excessive engine revving when cold.

Spalling will ultimately weaken the bearing and fracture it, leaving behind a jagged depression (or a ‘pit’). Once this cycle begins, wear is greatly accelerated and the bearing will fail very quickly.

What Is The Worst Case Scenario?
In worst-case scenarios, the cam timing can also be thrown off, causing valve to piston contact. In that case, the engine will need a full tear down and rebuild.
Check the photos below for what severe failure looks like.

An once of prevention (as in a replacement IMS bearing, BEFORE failure) is worth a pound of cure.
One thing is for sure; once you have experienced an IMS bearing failure, there is NO turning back.
A complete engine disassembly is required to replace the intermediate shaft and in most cases, complete rebuild or engine replacement is your ONLY option.

What Can Be Done To Fix This Common Problem?
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 and minimize the risk of a costly engine failure. With model year 1997 through 2005 engines, the bearing is indeed readily accessible with engine removal.

An IMS bearing replacement is intended to be installed as a pro-active measure in preventative and regular maintenance. Once an engine has suffered a failure, replacement of the intermediate shaft bearing is no longer an option. Installing a replacement IMS bearing in an engine that has already suffered a failure will result in a subsequent failure due to collateral damage, including but not limited to debris contaminating the new bearing.

Are There Any Warning Signs? 
There are three warnings signs which can indicate a bearing is failing; you’ve found metallic debris in the oil filter while carrying out an oil change, which means you actually have to open up and carefully examine the pleats. These may initially appear as fine flecks, rather than large particles.

You may have found that there’s an oil leak located at rear of engine, in the area of the rear main seal.
Or perhaps have started to hear knocking and metallic sounds coming from the rear of the motor.

It’s important as soon as you spot or hear the problem, call us at (207) 882-9969 for some advice.
Please do not drive the car until it has been inspected by a trained Porsche technician, as you could cause catastrophic engine damage and failure.

The Only Correction Is Prevention
An once of prevention (as in a replacement IMS bearing, BEFORE failure) is worth a pound of cure.
If your Porsche qualifies, and the IMS bearing has not been replaced with an update kit in the last 30,000 miles, we strongly advise you do it proactively.
Do not wait, time is engine. Your engine.

Likewise, if your IMS bearing has been replaced 30,000 to 40,000 miles ago, it’s time to do it again, don’t wait until it fails.
The replacement bearings, though very good, and very durable, do wear out, and can fail like their OEM predecessors.

Need More Help?
We hope we’ve been able to shine some light and help you have a better understanding of what exactly an IMS bearing is and what can actually go wrong with them. And more importantly, how to prevent that from occurring! To discuss the best approach for your car, give our service team a call us or email

Questions, or if we can be of help in any way with service on your Audi, BMW, Mercedes, Mini Cooper, Porsche or other European import, please contact us. Our team of Service Specialists is here to help, for even the newest autos! (207) 882-9969.

Knowing, not just “doing,” that’s the Atlantic Motorcar Center way.

The Atlantic Motorcar Center Service Team

Photos of Atlantic Motorcar IMS Bearing Installation – Porsche Boxster

Photos of Classic IMS Bearing Failures


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