My Intermediate Shaft Bearing: Porsche 911 (996) Saga

Garett Pereda

Or: “How I Learned to Stop Worrying and Love the 996”

“How was that?” She looked at me wide-eyed. Expectant. I wiped my glistening forehead, struggled to steady my breathing. “It was good, ”I squeaked, my cracking voice belying my intent to play it cool.

I didn’t want to let on that I liked the car as much as I did, but my mind was racing over the canyon roads I’d just slalomed — already calculating the potential value of my trade. How much of a bath could I afford to take on the negative equity? What about service records? A pre-purchase inspection? What would I tell my wife?

None of that mattered. I wanted the car. A 2002 Porsche 911 Carrera. And at that moment, only a stack of paperwork, money owed on a 2016 Mazda Miata, and a fresh bank loan stood between me and the car-guy holy grail of 911 ownership.

Hello, my name is Garett and I have a problem. The saleswoman gave me a satisfied once-over. I could tell by the curl at the corner of her lips that I was at her mercy. But as we stepped from the 996 and headed toward her office, a kernel of reason popped in my brain, “Has the IMS been addressed?” The woman stopped in her tracks. She turned, slumping her shoulders, avoiding my gaze. “We… don’t have a record on that.” Damn.

Porsche 911 (996) side (photo by Danny Nikkhoo)

For readers who are not as steeped in the Cult of Porsche as those of us who worship the holy pigs of Stuttgart, the 996 generation of the iconic 911 is the least-loved iteration for three primary reasons. First, it marked the end of the air-cooled era for Porsche, as it was the first water-cooled 911 (gasp). Second, it has headlights that aren’t round (seriously). Third, and most significantly, if left unchecked, the engine in this generation 911 has the potential to grenade due to an (arguable) design flaw at the rear of its case. A faulty IMS bearing. Which, in this particular car had been left unchecked.

I looked back toward the 911, fighting a rising desire to follow the saleswoman into her office anyway, to take on the risk, and take on the debt. But in the great struggle between angel and devil on my shoulder, angel won… for now. “Let me sleep on it.”

Fear the Forums

Porsche 911 (996) haunch (photo by Danny Nikkhoo)

But sleep never came. I spent the night scouring the Internet, hoping to justify the purchase I’d already made in my mind. I was going to find evidence that the 996 IMS issue was overblown. That the consequence of failure wasn’t as severe as I’d been led to believe. I was going to quieten Porsche purists the world over who lifted their noses at first sight of the ‘fried-egg 911’! What the hell was an IMS bearing anyway? It sounded like a small part. How bad could it be? And then I clicked on the forums: Rennlist, FLATSIXES, 6SpeedOnline

Have you ever had a toothache, a swollen gland, a pus-laden scab on your knee, and run a WebMD search on your symptoms? Don’t. It doesn’t matter what actually might be ailing you, the Internet will assure you of your terminal cancer. Perusing the forums on the 996 IMS issue is a bit like that. “Don’t buy this car,” they’ll tell you, “It’s only a matter of time.” “Your engine will explode.” “You will die.”

So, considering I couldn’t afford to risk a catastrophic engine failure in a car I was taking a note on, I did the only logical thing any well-educated, reasonably intelligent person would do.

The next day I drove to the dealership and bought the 911.  [Angel 1 : Devil 1]

IMS, Shmi-MS

Porsche 911 (996) front (photo by Danny Nikkhoo)

If you’re a fan of AlphaLuxe, chances are you’re enough of a gearhead to have heard the infamous acronym: “IMS.” Maybe you’ve even gone down the same Porsche pre-purchase rabbit-hole that I did. I feel you, soldier. But I’m willing to bet that many of you, like me, have been fed misinformation about Porsche’s so-called self-destructive engines circa 1999 – 2008.

Well I’m here, dear reader, to provide you with something I never had: A level-headed approach in defining the problem, quantifying its scope, and determining whether or not you should purchase that hot little M96/M97 Porsche 911 (or Cayman or Boxster) you have your eye on. But first, some definitions…

For help with the technical bits, I phoned my local Porsche expert, Marco Gerace. Marco runs a well-regarded independent Porsche repair shop, TLG Auto, based in North Hollywood. He inherited his trade (and shop) from his father, who started the family-run business over forty years ago. He also builds transmissions for a certain 356-Outlaw coachbuilder named Rod Emory. Needless to say, Marco has some serious P-car street cred.

“IMS,” Marco explained, is short for “intermediate shaft,” and like its name suggests, it’s a “layshaft that’s run off of the crankshaft and it [indirectly] drives the camshaft[s] via chain[s] and gears.” This intermediate shaft design is not unique to the 996. In fact, the IMS is found in all Porsche flat-six engines, from the first 911 in 1963 through the end of the first generation 997 in 2008. So it follows, as Marco affirmed, that the IMS in the 996 is not actually its problem. It’s the bearing that supports it. “That bearing was a weak spot and somewhat prone to failure. The question has always been: Why?”

The IMS bearing in the 996 is sealed with factory grease meant to provide adequate lifetime lubrication but “over time, that seal gets compromised either due to lack of maintenance, or temperature, or contamination in the oil… [and] once that seal was compromised, oil from the motor would get in and wash out that internal lubricant. The problem was that the compromised seal wasn’t sufficiently destroyed to allow proper lubrication, so the bearing would start to eat itself.”

If you’re a current or prospective 996 owner and a masochist or you simply have a prurient desire to see what happens when this bearing “eats itself,” look no further than the forums. There exists, in the darkest reaches of the Internet, a cache of horrifying post-mortem photos of shredded ball bearings that wreaked havoc on unsuspecting owners’ glorious flat-sixes. Doubtless these images have contributed to keeping the market value of the (996) Porsche 911 right around the MSRP of a new Toyota Camry.

Not Just the 996; Not All 996

Porsche 911 (996) cockpit (photo by Danny Nikkhoo)

But let’s clear a few things up right now.

This “fault” is not limited to the much-maligned 996. Sure, this model bears the brunt of the Internet’s animus but the same basic IMS bearing design was present in every M96 and M97 boxer-six that Porsche produced from 1999 – 2008. This means that every Carrera, Cayman, and Boxster produced during this era has the potential to go “boom.” Yes, including the world’s favorite liquid-cooled porker — the M97-based 997.1 (produced from 2005 – 2008).

On the forums, you’ll find much debate about the changes in IMS bearing design from the dual-row ball bearings of MY 1999 (M96), to the single-row design used between 2000 – 2005 (also M96), versus the larger single-row bearing used between 2006 – 2007 (M97). Armchair mechanics praise the relative strength of the factory dual-row and larger single-row designs over the smaller single-row bearing produced between 2000 – 2005. Anecdotally, failure rates appear to occur at a higher frequency for MY 2000 – 2005, which would support this theory. But Marco wasn’t having any of it.

“No… you can’t separate M96 and M97… they are the exact same basic design, with the same style intermediate shaft… they need to be lumped together. In terms of total production number of cars that have failed, you can’t separate the two.”

I asked Marco to estimate the scale of the problem (Porsche Cars North America did not return my request for comment on this point). “I believe the official number [of failures] are about 3% of total production, maybe a little higher, maybe 4 – 5% of total production of all M96 and M97 motors.”

So, liberally, we’re talking 5% of hundreds of thousands of cars produced from the following model ranges:

• MY 1999-2001 996.1 911 (C2, C4, Coupe, Cabriolet, and Targa Variants)
• MY 1999-2004 986 Boxster (Base and S Variants)
• MY 2002-2005 996.2 911 (C2, C4, C4S, Coupe, Cabriolet, and Targa Variants)
• MY 2005-2008 987 Boxster (Base and S Variants)
• MY 2005-2008 987 Cayman (Base and S Variants)
• MY 2005-2008 997.1 911 (C2, C4, C4S, Coupe, Cabriolet, and Targa Variants)

Which means at least 95% of the cars listed above have never, and will never experience IMS bearing failure. So if you’re thinking of purchasing one of these cars without a service record for IMS replacement, know that there is an extremely low likelihood that your IMS will “grenade,” even if your engine was left completely stock. What’s more, it appears that most engines that did fail were of low mileage, and typically were insufficiently pushed to circulate engine oil, contributing to a higher failure rate. This may be another case where it’s better to buy the “driver’s car” over the “garage queen.”

It is also worth noting that none of the GT and Turbo variants of 996 and 997’s produced during this era carry the potential for IMS disaster, because, as Marco pointed out, “they still ran the Mezger motor**, which is the same basic design as the air-cooled motors. They had the same bottom end with the same case, crank and rods as earlier cars.” Which, may be enough of a selling point to justify your doubly expensive purchase of a second-hand 996 Turbo. If I could swing it, I’d have one of those.

[**Editor’s Note: The ‘Mezger motor’ term is a misnomer because Hans Mezger has been designing Porsche engines since 1956. Amongst modern Porsche enthusiasts, the term has become synonymous with the engine fitted to Porsche 911 GT3 cars, before the 991 generation.]

Warning Signs

Porsche 911 (996) dashboard (photo by Danny Nikkhoo)

But what if you own, or are thinking of purchasing one of the affected cars listed above? How would you know if you’re in the unlucky 3 – 5% that fail?

Unfortunately, you won’t… until you do. When the IMS bearing begins to shed, it circulates debris throughout the motor, so “you [can] inspect the [oil] filters, you [can] pull the sump plate down if you’re really questioning things and you can look inside [and] see if there’s any material in there.” And because the IMS drives the camshafts, “you can also check for camshaft deviation values, which are numbers that tell you what the cam timing is actually running at [versus what it should be running at] in relation to the crankshaft.” This measure doesn’t exactly tell you that the bearing is bad, Marco warned, “but it points you in the right direction.”

And if the bearing is bad? “Some people say it’s too late, others say it can be saved. It really depends on how much material the bearing is shedding.”  Which is why, despite the low risk of failure, it’s probably best to address the IMS before it shows any sign of failure.

As the bearing is located near the rear main seal and clutch assembly, it makes sense to address all three service items in one pricey trip to your friendly neighborhood P-car technician. Which, is exactly what I decided to do.

Nearly seven months into 996 ownership, I was as tired of suffering through a worn clutch in L.A. traffic as I was living with the blown-bearing guillotine hanging over my head, so I finally decided to end the madness and address my IMS.

The Solution

My Intermediate Shaft Bearing Porsche 996 Saga side (photo by Danny Nikkhoo)

There are several companies that offer an IMS fix, but the best known and most respected is a firm called LN Engineering in Chicago. LN offers two alternative products to tackle the pesky IMS bearing – “IMS Retrofit” or “IMS Solution.”

The “Retrofit” is cheaper; the factory bearing is swapped for a stronger, re-engineered dual-row bearing. But as Marco described in our pre-procedure consultation, this product has a service life. “I think maybe 50,000 miles and then they suggest you replace [it] again.”

This didn’t thrill me. I wanted to tackle the IMS once and for all, so Marco advocated “The Solution.” This fix “basically turns the IMS roller bearing into a plain bearing.” It removes the rollers and grease, then adds a pressurized oil feed, “[making] it more like a standard main bearing in a crankshaft.” Once installed, this kit “requires no further maintenance until the motor gets rebuilt completely…. It’s a great thing, it just solves the problem.”

Sign me up. And off to Marco my happy little 996 went, about to get a new lease on life.

Plot Twist

Porsche 996 steering wheel (photo by Danny Nikkhoo)

A few days later, I received an ominous call. “Did you get my email?,” Marco asked. He sounded stressed. Uh oh.

“No, what’s up?,” I demanded, nervously anticipating that Marco had found metal in my oil filter, that this whole exercise was too little, too late; that I’d owe the better part of thirty grand on a glorified paper weight, and that my wife would kill me.

“Let me re-forward it. Basically it explains why I can’t install the IMS Solution.” When I couldn’t respond, my heart firmly lodged in my throat, Marco qualified, “Don’t worry, it’s a good thing.” It turns out, my 996 had a factory remanufactured motor. Meaning that its original motor went kaput… probably due to an IMS failure!

I called PCNA with VIN and engine serial numbers in-hand to definitively determine the cause of death, and to get an official record of the replacement, but they didn’t have the info in their system. “The work was probably done through an independent shop,” they told me.

But why couldn’t Marco install the Solution on the ‘Re-Man’? “In short,” he wrote, “your engine is equipped with the non-replaceable OEM bearing that’s typically found in the 2006 and later motors.” He’s referring to the 997.1 IMS setup with the larger single-row bearing. But why would that setup be installed onto my 996?

“When Porsche supplied factory ‘Re-Man’ motors they always used the newest components… in this case, the non-replaceable IMS bearing setup. The protocol is to remove the IMS cover and remove the seal from the bearing so that it is no longer a sealed unit and can instead receive splash lubrication.” He assured me, “To date, no engine that I know of that’s had the seal removed has had an IMS bearing failure.”

So I have a factory refreshed 996 engine using 997 components. My motor has less than the 73,000 recorded miles on my odometer, and this surprise turn of events saved me $1,500 in parts and labor. I should play the Lotto.

Ist Fertig

My Intermediate Shaft Bearing Porsche 996 Saga ist fertig (photo by Danny Nikkhoo)

Before going down this IMS journey, I had convinced myself that with over 70,000 miles, my engine was probably fine. I’d thrashed the hell out of it during the seven months of my ownership and never sensed a hint of anything wrong.

But learning that the engine in my 996 had been replaced with a factory Re-Man opened my eyes to the fact that although the likelihood of this fault occurring is small, the gravity of an IMS failure is very high. A Re-Man motor for a 996 costs about as much as I paid for the car, meaning that if the engine had died while I owned it instead of before, I would be looking at a $50,000 Porsche 911 — something that I frankly couldn’t afford.

If you’re thinking about buying an M96 or M97 Porsche, make sure you have a service record for an IMS ‘Retrofit’ or ‘Solution’, or get it done at the start of your ownership. For 3 – 4 grand, it will give you piece of mind and increase the value of your car.

Is the 996 IMS issue overblown? Almost certainly. The Internet has done Porsche no favors in the PR department. Marco put it best, “When you go online… [people are] more likely to share the negative than the positive. So you get 50 people together, and of those 50 people, most of them have had a problem. It seems that there are an overwhelming number of problematic cars. It’s a ‘sky-is-falling’ mentality. But the reality is the sky is not falling… they’re actually very, very good cars. They just have a weak link.”

As a happy owner of a healthy 996, I’m relieved this weak link is something that can be addressed. In my opinion, you can’t have more automotive fun for under $30k, even if you have to shell out a few extra grand to ensure your example lives a long, high-revving life.

Enthusiasts the world over: Raise your glasses, and long live the fried-egg porker!


Author’s Biography

Garett Pereda became a petrolhead the moment the boost in his father’s Porsche 930 first threw him back in his seat when he was four years old. He’s been chasing that rush ever since. After graduating from NYU and Pepperdine Law School, Garett worked as an entertainment attorney at William Morris Endeavor before diving headlong into his life’s work — pursuing a career in television writing. He is a proud member and union captain for the Writers Guild of America, having worked on shows for Netflix, Warner Bros., Blumhouse Productions, Ellen DeGeneres, Lawrence Bender, and others. He lives in Los Angeles with his wife, step-son, and their long-haired cat, Kiku.

About Garett Pereda

Garett Pereda is a contributor on the AlphaLuxe team. View all posts by Garett Pereda →

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