IMS Anxiety

The Sky is not Falling

By Robert Moniz, UCR Treasurer (from Provinz February 2014 page 26)

A lot has been written about the Intermediate Shaft (IMS) bearing issue facing the M96/ M97 engine. The negative press found online, and in various car magazines is definitely creating fear, uncertainty and doubt among owners of Boxsters, 911s (non-GT3 or Turbo), between model years 1999 and 2008. First generation Caymans also used an IMS bearing. I’d like to share what I learned when I decided to inspect my 911 C2S (997.1).

My situation, along with anyone else who owns a model year 2006 to 2008, seemed especially frustrating. During this period, Porsche decided to use a bearing with a diameter so large that it cannot be removed from the engine without dismantling the block. Going in, I knew if the bearing was damaged, I’d be facing a long battle in the off-season trying to claim the repair (engine rebuild) under the class action settlement in the US. More on that later. For the previous model years 1999 to 2005.5, the bearing can be removed and replaced with a similar OEM part or an improved higher-performance ceramic bearing.

In evaluating my options, I settled on the following two: Take my chances, and put faith in the fact that very few 997 models have experienced a failed bearing, or use this as an opportunity to drop the transmission, inspect the IMS bearing along with the clutch, flywheel, and rear main seal (RMS) all at the same time. Given my car is tracked almost exclusively, I decided to perform the preventative maintenance. Mechanical peace of mind is very important when you’re exploring limits, lap after lap at the track.

A direct oil feed (DOF) solution from Pedro’s garage in south Florida has been discussed in previous issues of Provinz. Pedro is a great source of technical information for our members, but personally I wasn’t convinced that tapping into the engine’s oil system is something I wanted to do. Especially, when after speaking to Pedro, he informed me they’re working on second generation DOF to address issues with the original design. Instead, my goal was to gain access to the bearing, remove the black plastic seal, and inspect the health of the unit. If all is well, the seal would not be replaced, allowing oil to lubricate the carrier and bearing.

I ran this suggestion by my mechanic, Zoran, owner and operator of Zorotech in Stoney Creek, and he concurred. Zoran has replaced many IMS bearings over the last few years. His observations support the general consensus that infrequently driven cars that sit unused with poorly maintained fluids suffer the highest failures. Zoran recently acquired a 911 (996) with roughly 200,000 km on the odometer. Upon inspecting its IMS bearing, it appeared brand new (image below).

IMS bearing from a 996

An IMS bearing from a 996 – all photos by Robert Moniz

Being a 996, Zoran had the ability to replace the bearing, which he did with an improved ceramic version. For those unfamiliar with ceramic vs. steel bearings, here are some key benefits:

  1. They last 10 to 50 times longer than steel.
  2. They require less lubrication.
  3. They are corrosion-resistant.
  4. They withstand heat better than steel.
  5. They do not conduct and are not susceptible to magnetism.

For more background on ceramic bearings, author Rainy Ling has a great article which can be found at EzineArticles. com/4880482.

It baffles me why Porsche decided to use a bearing in the 2006 to 2008 models that can’t be replaced without tearing the engine completely apart. For a car that’s been combed over and improved upon for over 50 years, this seems short-sighted.

I was pretty anxious on the day of the scheduled service.  Was my car sick? Why didn’t I buy that GT3 when I had the chance? Who knew the 996 was easier to maintain? Before emotions got the better of me, I decided to focus on the positive aspects of deciding to do something about it and not ignoring the potential issue.

When I arrived at the shop, Zoran had already removed some of the parts around the engine and transmission. The cover was off the oil pan and I was amazed at the condition of the oil compartment. Everything looked brand new! It wasn’t long before the transmission was removed, along with the clutch assembly. All of these, including the flywheel were neatly presented on the workbench for inspection.

With 75,000 km, the clutch showed less than 30 percent wear. I bought the car from fellow members Horst and Marie Petermann. It pays to buy a car from someone you know, especially a fellow enthusiast. The pressure plate and flywheel were in great shape as well.

Now came the moment of truth. I could see the dreaded IMS flange cover. Its image burned in my memory from the countless hours of surfing the internet. Sure enough, oil was seeping from its bottom edge. I took comfort in the fact that within the 10,000 km that I’ve owned the car, the oil has been changed 4 or 5 times. Therefore, I knew that bearing wasn’t sitting in rancid (acidic) oil. Knowing Horst and Marie keep their cars meticulously maintained at Mantis in Oakville, I also felt pretty good about the mileage during their ownership.

Within minutes the flange was removed, and we could perform our first test on the bearing—wiggling the small shaft in the centre. Would you believe it felt brand new? Zoran pulled a couple bearings from his inventory to compare the feel. They felt identical to the one that’s trapped in my engine block.

The remaining step during the inspection was to remove the black plastic cover sealing the bearing. It should be noted that removing this cover is not an official recommendation by Porsche. However, the physics support removing this barrier to allow [clean] oil to lubricate the bearing. Besides, seeing oil seeping from the bearing tells me whatever grease used to be packed in there is long gone.

IMS Article - Picture - Zoran removing bearing cap - Credit = Robert Moniz v2

Zoran removing bearing cap

With extreme care and precision, Zoran used what looked like dental tools to remove the seal. Once removed, the last milestone of relief was felt. No corrosion. Nothing but smooth spinning parts in a film of oil. All that anxiety was now put to rest. This car has a long and happy life ahead of it. High-fives all around!

IMS Article - Picture - Zoran Thumbs Up v2

Bearing is OK, Zoran gives the thumbs up

A quick discussion ensued and we decided to replace the rear main seal (RMS) and clutch plate while we had every- thing apart. Even though the clutch plate was slightly worn, I decided to order a new one because there’s no foreseeable reason to drop the transmission again within the next 100,000 km. The RMS seemed fine, but for $20, it seemed like a no brainer to replace it. The pictures below compare the encased IMS bearing in a 2006 911S with its outer seal, and with it removed.

IMS Article - Image 2a - Bearing v2

IMS bearing with seal and (below) without

IMS Article - Image 2b - Exposed Bearing v2

Here’s a breakdown of the costs incurred:

  • IMS Flange Gasket        $20
  • Clutch Plate                  $300 (optional)
  • RMS                              $20 (optional)
  • Labour                           $534 (6 hours)
  • Peace of Mind              Priceless!

 

Given the financial and sentimental value our objects of desire engender, the minimum outlay of $554 is a small price to pay. Many members pay more than that for a couple oil changes at their dealership of choice. Obviously, prices will vary based on different shops and vehicle situations.

There is an alternative to dropping the transmission to inspect the bearing. Since the IMS’s purpose is to drive the shaft chains, a diagnostic test can be performed to measure variances (if any) between the cam shafts’s timing. A healthy reading would show no difference between the cams. If a difference occurs, then more inspection will be required. This could also be due to another ticking time bomb; the cam chain guides.

I find it interesting that in all the material I came across, I’ve yet to find mention of another key component in the cam shaft timing system—the chain guides. As the IMS turns the chains that spin the cam shafts, the chains ride on a plastic runner. Given the chain is metal, and guide is not (plastic), friction due to old rancid takes its toll over time. The image on the left below shows what a new guide looks like; on the right is one with roughly 150,000 km on it. This is an example of a neglected engine. The [dirty] chain chewed right through the guide. Cars affected by this plastic guide system are model years 1998 to 2002 (3.4L).

I’d be remiss if I didn’t mention another important service item which is often overlooked, the air oil separator. I’m sure many of you have seen puffs of dark smoke leaving the car ahead of you when they step on the throttle. That’s due to oil in the combustion chamber. Dirty oil wears down the membrane in the air-oil separator, resulting in oil going where it shouldn’t. So there’s a common theme here. Change your oil often. It’s very cheap insurance.

Fortunately, my situation didn’t end up in a claim with Porsche Cars Canada. I’m not sure how that would have turned out because the class action settlement in the US is currently limited to US customers. Porsche Cars Canada is handling claims on a case-by-case basis. The US settlement also has the following restrictions:

 

  • Only model years 1999 to 2005 are covered.
  • Age of car limited to 10 years.
  • Non certified pre-owned cars are limited in coverage.
  • Coverage also prorated based on mileage.
IMS Article - Image 4 - Used Cam Chain Guide v2

Worn chain guide from dirty oil – photo by Robert Moniz

IMS Article - Image 3 - New Cam Chain Guide - Credit = ECS Parts

New chain guide – photo courtesy of ECS Parts

 

 

 

 

 

 

 

At the time of writing, 35 percent of UCR’s members have cars with M96/ M97 engines. For those who haven’t addressed the issue, do yourself a favour, and change your oil while you contemplate your next steps.

 

1 thought on “IMS Anxiety”

  1. Hi Robert:
    I enjoyed the article, but I have two points to clarify:
    a) you say: “speaking to Pedro, he informed me they’re working on second generation DOF to address issues with the original design”
    After the patent for the DOF was applied for there have been no other mods on the design because there have never been any issues with the original design.
    What we are working on are alternate oil pickup points that would also allow for pressure/temp monitoring of the oil going to the bearing, but the DOF has not been redesigned.
    b) the only sure-fire way to know the condition of an IMS bearing is by cutting it open.
    There’s no wiggle test that can give you an accurate picture of what’s happening inside.
    I want to finish by saying that although we sell and promote the DOF System we acknowledge that 9 out of 10 cars get mis-diagnosed with an IMS failure.
    Happy Porsche-ing,
    Pedro

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