Written by: Bradley Hayes
Automotive Blogger & Director of Marketing, Autoscope European Car Repair
The Porsche IMS Bearing – Small Component, BIG Problem
Have questions about the infamous Porsche IMS bearing? You’re not alone. By now, most (if not all) Porsche 911 owners have heard about the Porsche IMS bearing issues that have plagued these engines for years. However, if you own or are considering purchasing a 996 or 997 generation Porsche 911 (excluding Turbo models), or a 986 or 987 generation Porsche Boxster, and aren’t already aware of the “IMS bearing upgrade” then we urge you to keep reading because the information you’ll find here could very well save you thousands.
There are countless forum threads and search results on the web regarding this subject, and many either have conflicting information or just seem to confuse the topic even more. Many readers are still left wondering about the real answers to their questions. “What causes IMS bearing failure?” “How can you tell if your Porsche IMS bearing needs to be replaced?” “Can IMS bearing failure be prevented?” “What is the Porsche IMS bearing failure rate?” We’re here to help clear the air and settle the matter for good. No hearsay, no second-hand anecdotes, and no armchair engineering – just the facts. You don’t want a dissertation or more dubious speculation; you want to be informed and you want to know how to safeguard your Porsche from premature catastrophic engine failure caused by a failed IMS bearing. So, without further adieu, here is everything you need to know about the Porsche IMS bearing problem.
First things first, a little basic information is in order before we get down to the nitty-gritty…
What Is the Porsche IMS Bearing?
Failed Porsche IMS Bearing
If you read the words “premature catastrophic engine failure” above, your first thought might have been to wonder exactly how such a relatively small component has the potential to lunch an entire engine, instantaneously, and seemingly with no warning. Without getting too technical, we’ll briefly go over what an IMS bearing is and what its function is.
For starters, “IMS” stands for intermediate shaft. The intermediate shaft is basically a geared shaft that runs through and extends out from the front and rear of the engine. By way of those gears, the function of the intermediate shaft is to use the mechanical rotation of the engine’s crankshaft to indirectly drive the camshafts on either side of the engine. The actual intermediate shaft itself, however, is not the root of the now well-known and infamous 996 and 997 IMS-related “engine problems.” The basic design and use of an intermediate shaft was by no means a new development in the then-radical and new water-cooled “M96” engine developed for the 996. In fact, the intermediate shaft has long been a feature of the horizontally-opposed (also known as a “boxer” configuration) flat-six engines for which the Porsche 911 is so famed, as long as the 911 has existed, in fact. Up to this point in the long timeline of the evolution of the 911, the incorporation of an intermediate shaft on Porsche’s flat-sixes, in both concept and practice, had been tried and true. With the advent of the M96 and the early production runs of the later-revised “M97″ engines, the rub (pun intended) is in the sealed cartridge-style ball-bearings that support the IMS, more simply referred to as the “IMS bearings.”
If Your IMS Bearing Fails, You’re Going to Have a Bad Time
The main weaknesses inherent to the factory-original IMS bearings can be attributed to two glaring deficiencies: 1.) The material the ball-bearings are constructed with is not quite strong enough to withstand the physical and thermal loads exerted upon them, and 2.) the lubrication of the bearings is insufficient.
It has been verifiably documented that some IMS bearings have failed after just 3,000 miles.
More carnage from a failed Porsche IMS bearing.
There can be many contributory reasons for IMS bearing failure and often it is a combination of causes that ultimately results in bearing failure. The exact rate of failure of these IMS bearings is tricky to nail down with any certainty. Claims of which, especially those made by unqualified “experts” or ones found in the myriad forum threads about this topic, can vary drastically, however, reliable sources have reported the failure-rate of some of these original bearings to be estimated as high as an astonishing 10% after an average of just 90,000 miles. Since it has also been verifiably documented that some IMS bearings have failed after just 3,000 miles, while others still have lasted for 200,000 miles or more, the only safe conclusion that can be drawn is that all M96 and some M97 engines in Porsche 911’s (996 or 997), and all Boxsters (986/987) from 1997 through 2008, are at risk of suffering IMS bearing failure at any time, irrespective of mileage.
Motor wird dann sein kaputt!
Once an intermediate shaft bearing fails, options quickly become few and expensive. The absolute best-case scenario (and least likely) is if only the intermediate shaft and bearings need to be replaced, and even that still involves a complete engine removal, inspection, and disassembly.
In the worst-case scenario, IMS bearing failure can disrupt the cam timing causing impact between the pistons and valves, resulting in shattered valves, smashed pistons, and other extensive engine damage. The majority of the time then, your only option is to totally rebuild the engine or replace it in its entirety, at not inconsiderable cost for either.
Pictured: Worst-case Scenario
How to Know If Your Porsche Is at Risk for IMS Bearing Failure
The IMS bearing for these engines went through multiple design revisions from 1999 – ’06, including both single- and dual-row bearing designs, without ever adequately resolving the issue. Eventually, the M96 and M97 engines were replaced by the “9A1″ engine, the first 911-bound engine to completely dispense with the intermediate shaft system altogether in favor of a system that drives the camshafts directly off the crankshaft. That’s great news if you bought a 911 from the 2009 model year or later which has the newer 9A1 engine, but what can you do if you own a 911 with an M96 or M97 engine to prevent IMS bearing failure? And what if you’re looking to buy a pre-owned 911, how can you protect yourself from falling victim to a failed IMS bearing?
A Porsche Expert’s Professional Advice for Preventing or Avoiding Porsche IMS Bearing Failure
In any case, fear not because fortunately there is a solution. And that solution comes from LN Engineering in the form of the “LN IMS bearing retrofit” upgrade. LN Engineering is the largest and most reputable name in the manufacture of Porsche IMS bearing replacement upgrades and they are our exclusive source for the hundreds of IMS bearing upgrades and replacements that we have performed and continue to perform regularly. The design, materials, engineering, and serviceability of the LN IMS Retrofit upgrade virtually eliminates the risk of IMS bearing failure and the consequent gargantuan repair costs.
Advice for Owners
For 911 owners, our recommendation is to find a qualified Porsche repair specialist and have the IMS bearing upgrade performed on your car. We don’t advise rushing out to immediately have it done before putting even one more mile on your engine, necessarily, but it’s probably best to go ahead and do it at the same time another procedure is done, like a clutch replacement, rear main seal, or any other job where there is a lot of overlapping labor involved that you can take advantage of to save money. Planning in this way means you can still enjoy your Porsche without the looming anticipation of imminent engine failure with every squeeze of the throttle. In addition to your own peace of mind, it will preserve the resale value of the car when the time comes to sell. Most savvy prospective buyers won’t even consider purchasing a car that doesn’t have an IMS upgrade in its service history, and if they do, you can and should expect to have to significantly lower the asking price.
Advice for Buyers
For prospective buyers, our advice is to do your homework beforehand, and proper due-diligence when considering any one car. Always ask to see the service history of any pre-owned car you’re considering to buy, but it’s especially critical for someone looking at one of these pre-owned 911’s to ascertain if an IMS upgrade has been performed. If it has, great! If it hasn’t, that doesn’t necessarily mean you should automatically pass on the car but it should be a major consideration to weigh. It’s up to you if you decide to pursue it further and if you do, know that you can reasonably expect a much lower price on the car for having to get the IMS upgrade performed yourself, as well as for the increased risk associated with a car that hasn’t yet had it done. In either case, always find a qualified Porsche specialist to perform a pre-purchase inspection on the car before you buy it. Walk away from any seller that seems hesitant, or flat refuses, to allow a pre-purchase inspection. Suspect, too, is the seller who will agree to a pre-purchase inspection but only on the condition that it is performed by a mechanic or shop of their choosing. And as always, be wary of any deal that seems “too good to be true” because it almost always is.
To learn more about the Porsche IMS bearing upgrade or to have one performed on your Porsche 996, 997, or Boxster, give the European auto repair experts at Autoscope a call or set up an appointment online today!
© 2015 B. Hayes & Autoscope European Car Repair
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