996 IMS Issue - How real is it?

[Rod C]

I spent two and a haif years looking at 996's and 90% of the owners had no idea of the issues with these cars but does make a great bargaining tool when its time to negotiate a deal and like most informed buyers of a 996 it was sraight off to have the IMS sorted.

[quasio]

Just as data point - recently did the ims solution car had 135k kms.

ims looks pretty good actually (actually looks new to me), seals intact etc.  ( i haven't removed them) 

no play except for when i put a kind of yaw motion on it but it's super slight. it's also the single row one. 

Spoke to the mechanic (porsche specialist) and they've only done 3 (i think) over the years. A lot of people ask about them, but no one ends up doing it and mentioned they've only seen one failure from a boxster. 

So maybe it's more a US thing, with their harsher climates?

 

[Avon]

Had the IMSB replaced recently at 185k Kms as engine had to be dropped anyway to replace brake lines, get manifold studs and a new AOS.  Original IMSB seemed as good as new.  Replaced it with FVD Brombacher steel bearing.  1999 3.4 C2.  

Original IMSB for sale if you're feeling brave ?

[LS1RX7]

Just as data point - recently did the ims solution car had 135k kms.

ims looks pretty good actually (actually looks new to me), seals intact etc.  ( i haven't removed them) 

no play except for when i put a kind of yaw motion on it but it's super slight. it's also the single row one. 

Spoke to the mechanic (porsche specialist) and they've only done 3 (i think) over the years. A lot of people ask about them, but no one ends up doing it and mentioned they've only seen one failure from a boxster. 

So maybe it's more a US thing, with their harsher climates?

 

When I replaced mine the old bearing appeared fine and seals looked to be intact, however when I removed the bearing a substantial amount of black evil smelling engine oil came out of the intermediate shaft. The bearing felt ok but free spun more freely than you would expect a sealed for life bearing to spin, possibly indicating the original grease has been washed out by the oil that made it into the IMS. While it was still intact the life of the bearing ongoing would be limited now that it was lubricated by the oil that had made it past the seal and would have been deteriorating in the bearing without being replenished. Fortunately for me the bearing hadn't started to fail but I guess it would only be a matter of time. As for possibly only being a US problem, I doubt it. I believe poor design idea that shows itself occasionally regardless of climate. I'll stand by upgrading as a maintenance item for peace of mind.

Just as data point - recently did the ims solution car had 135k kms.

ims looks pretty good actually (actually looks new to me), seals intact etc.  ( i haven't removed them) 

no play except for when i put a kind of yaw motion on it but it's super slight. it's also the single row one. 

Spoke to the mechanic (porsche specialist) and they've only done 3 (i think) over the years. A lot of people ask about them, but no one ends up doing it and mentioned they've only seen one failure from a boxster. 

So maybe it's more a US thing, with their harsher climates?

 

When I replaced mine the old bearing appeared fine and seals looked to be intact, however when I removed the bearing a substantial amount of black evil smelling engine oil came out of the intermediate shaft. The bearing felt ok but free spun more freely than you would expect a sealed for life bearing to spin, possibly indicating the original grease has been washed out by the oil that made it into the IMS. While it was still intact the life of the bearing ongoing would be limited now that it was lubricated

Had the IMSB replaced recently at 185k Kms as engine had to be dropped anyway to replace brake lines, get manifold studs and a new AOS.  Original IMSB seemed as good as new.  Replaced it with FVD Brombacher steel bearing.  1999 3.4 C2.  

Original IMSB for sale if you're feeling brave ?

I'm pretty sure you're being humorous there. Even inserting a new bearing and then removing it without using it will render it defective as the pulling force on the bearing during removal is likely to cause small flat spots on the balls that will quickly increase during use and likely cause a devastating failure. When you install a bearing the forces are applied to the outer shell but when removing you are pulling from the inner collar.

[Avon]

Yes you'd be insane to reinstall the used one!

Here it is.  NSK made in Japan.

 

 

FYI this is the Brombacher bearing.

 https://www.fvd.net/de-en/FVD10590104/intermediate-shaft-ims-repair-kit-m96dual-row.html

[quasio]

Here's my badge of honor.

Interestingly it's an NSK part made in England!.

doesn't spin super freely so i think there's still grease in there.

[dan_189]

Whats the lifetime like on the FVD bearing? 

[Avon]

 

Have just been having useful email discussions with FVD, who confirm that the only options they supply for single row IMSB is the ceramic bearing.  This is NOT the LN Engineering option, but their own supply.

They say in advertisement that 100k kms is the minimum expected life for both options.

 

[Pokiou]

There is a guy on the petrol head forums called POP POP BANG BANG. I've spoken to him about the IMS bearing issue and to be honest it didnt phase him as his done 550,000 on the original bearing. Dual Row, the guy is a F1 engineer and drives his Porsche around the euro roads to deliver last minute parts and so forth. He said that most of if not all the faulty ones are from cars that sit all winter and barely get driven. I'd take and F1 engineers word over a lot of work shops. I understand people freak out about the IMS which is justifiable as its a costly repair/replacement. However, if you're buying a 996 to have it sit in the garage then its more then likely going to seize something and that something is the IMS bearing.

[Peter M]

I reckon its related to engine speed.  At lowish revs the torsional vibration in the IMS causes the balls to skid rather than roll and this causes the bearing to fail.  With the revs up, the vibration reduces and the bearings last. 

[LS1RX7]

I replaced my bearing myself and discovered that the bearings seals had failed and allowed oil to accumulate in the intermediate shaft. When removing the old bearing there was a substantial amount of black evil smelling engine oil that came out of the shaft. The likely scenario is the previous owner kept topping up the oil as the level dropped and due to failed seals in the IMS bearing the oil was gradually filling the shaft and every time you top up the oil you trap the oil that has made it into the shaft. This trapped oil then gets cooked again and again without the being filtered and eventually turns into an acidic, grungy substance. If allowed back into the bearing by a low oil level then it is likely to start to cause damage to the bearing due to poor lubrication and once a bearing suffers damage it will accelerate the deterioration with use ending up in a catastrophic failure.

It makes sense that cars that are driven infrequently suffer the most failures due to half the seal being immersed in oil and the other half allowed to dry while inactive for long periods, as the correct oil level is about halfway up the bearing. An open bearing with no seals such as the LN ceramic allows oil to pass back and forth through the bearing therefore the oil can't get trapped in the shaft and turn into the ugly stuff that came out of my IMS. I believe I was fortunate enough to escape disaster that would probably have been inevitable based on what I found.

[Pork Chops]

996s are a minimum of 13 years old. Likely the car you own has been owned by many before you. How could you possibly know how it's been driven and use this as a basis of a decision. Probably. Probably it won't happen, but if it does it's going to hurt your wallet badly. You insure things that are low probability but with high financial consequences (ie car insurance) so why apply a different logic to this situation? My first hand story is above and it was ugly for the owner. Would totally ruin the ownership experience. I would personally not consider owning one without it being done and consider it a necessary piece of preventative maintenance. It's also not THAT expensive either IMHO. The bill would be small compared to the $$ dropped maintaining those old aircooled cars. In the end it comes down to your temperament and how you see the world. My 2c. Wishing everyone the best of luck 

[LS1RX7]

Agreed, that is why I replaced the bearing in mine as a mater of urgency once purchased. Treat it the same way you would with a timing belt on other vehicles. Cheap peace of mind and makes ownership so much more enjoyable without that "what if" always niggling in the back of your mind.

[firstone]

Not the best thought out design but It's not bore scoring or broken head studs.

It's just a bearing to be replaced.

[Russ]

good article on pelican - http://www.pelicanparts.com/techarticles/Porsche-996-997-Carrera/13-ENGINE-Common_Engine_Carrera_Problems/13-ENGINE-Common_Engine_Carrera_Problems.htm

[Mike737]

Interesting little video which I found the other week. I'm sure it's already been covered on the renn forums before, not sure if on here though.

It makes reference to what @LS1RX7 was talking about with rancid oil inside of the intermediate shaft.

 

[Peter M]

The root cause of the failure isn't related to lubrication. 

If it was you would see similar rates of failure over the three different types of sealed bearings Porsche used over the life of this engine.  Further, you would see similar rates of failure between the Tiptronic and the manual transmission cars.

Also if the lack of lubrication flow/bad oil theory was the true, the commonly used open ceramic replacement bearings wouldn't have to be replaced in the remaining life of the engine either.

 

Irrespective of what you believe the true failure mode to be - TV or Voodoo, I'm with Porks, I'd change the bearing to preferably the plain bearing "IMS Solution" type and put this issue to be bed permanently.

 

    

[Mike737]

 I'd change the bearing to preferably the plain bearing "IMS Solution" type and put this issue to be bed permanently.

The IMS solution is a direct oil feed onto the bearing... so I'm not sure why you'd prefer the solution over just changing bearings after you just said the problem is not lubrication related.

That's one hell of a confusing argument you're making there 

[firstone]

They are all lubricated. 

To my mind the plain bearing is most likely a permanent solution therefore giving you and the next owner more confidence. 

Just like saying I replaced my broken head studs (all 24) in the A/C with the best known solution. 

[dan_189]

The IMS solution is a direct oil feed onto the bearing... so I'm not sure why you'd prefer the solution over just changing bearings after you just said the problem is not lubrication related.

That's one hell of a confusing argument you're making there 

There are two options from LN (among other vendors) but LN is the premium. 

Their IMS 'solution' removes the original bearing and replaces it with a 'plain' bearing - which needs to be oil fed to be lubricated. This is a solution for the lifetime of the engine as there are very few wearing parts. This plain bearing design is used to support the IMS (shaft) in the GT3 and TT engines. However the oil feed needs to come from somewhere so there is an adapter at the oil filter. Your engine bellhousing also needs a hole cut out of it to allow for the supply line to the bearing. 

The retrofit on the other hand replaces the original bearing to one of a similar design but with more robust components and in the case of single row bearings changes it to a dual row with ceramic coated ball bearings. This bearing had a finite life but is a direct replacement and no oil feed is required it is splash lubricated by engine oil. 

So in conclusion, 'solution' is lifetime and more expensive retrofit is cheaper but has a finite lifespan. Depends on your budget and plans for the car for which one you should choose. 

[Peter M]

The IMS solution is a direct oil feed onto the bearing... so I'm not sure why you'd prefer the solution over just changing bearings after you just said the problem is not lubrication related.

That's one hell of a confusing argument you're making there 

Mike,

The point I'm making is that a plain journal bearing copes with the torsional vibration that a bearing with rolling elements sometimes can't endure.

Imagine the wildly varying load at low engine speed that driving the valve train of 3 cylinders places on the shaft that is also compounded by its drive from the crankshaft being highly variable in its rotational accelerations as well.

Forget that plain bearings are often pressure fed, forget lubrication, it's the suitability of bearing type that is my point.

These issues are well known elsewhere in automotive engineering with the Ford DFV valve train reliability challenge probably the most famous example of destructive TV in practice.

 

 

[ANF]

For those with more time on your hands than me..... these guys are well known in the UK of knowing their stuff https://www.hartech.org/

https://www.hartech.org/images/downloads/Hartech Engine Guide (interim).pdf

[Zelrik911]

I dont have a W/C car but read this forum if I see something interesting.

I note that the original IMS bearing is a Japanese NSK, which does seem odd.

But wasnt it the Japanese (Toyota?) that 'helped' design the heads for the Boxster / 996 so they could be manufactured very much cheaper than a traditional flat 6 engine?

Perhaps this is how the NSK IMS bearing arrived and I wouldn't be surprised if that bearing has a has a close relative in 1990s Toyota somewhere.

[dan_189]

I've read a few similar things around Porsche learning to share more parts across models and cost savings around the transition from A/C to W/C as well.

I think the last article I read or video (can't remember) was that it was very expensive to manufacture the 993 compared to the 996. 

[Pokiou]

There are two options from LN (among other vendors) but LN is the premium. 

Their IMS 'solution' removes the original bearing and replaces it with a 'plain' bearing - which needs to be oil fed to be lubricated. This is a solution for the lifetime of the engine as there are very few wearing parts. This plain bearing design is used to support the IMS (shaft) in the GT3 and TT engines. However the oil feed needs to come from somewhere so there is an adapter at the oil filter. Your engine bellhousing also needs a hole cut out of it to allow for the supply line to the bearing. 

The retrofit on the other hand replaces the original bearing to one of a similar design but with more robust components and in the case of single row bearings changes it to a dual row with ceramic coated ball bearings. This bearing had a finite life but is a direct replacement and no oil feed is required it is splash lubricated by engine oil. 

So in conclusion, 'solution' is lifetime and more expensive retrofit is cheaper but has a finite lifespan. Depends on your budget and plans for the car for which one you should choose. 

GT3 and Turbo engines don't have  IMS bearing or an IMS.