996 intermediate shaft problems

[rattles]

Intermediate shaft failures seem almost as common as RMS problems but I have not been able to find any information on why they actually fail.

I have a 1999 996 C2 with 30,000 miles, the engine so far has not given any problems.

It would be interesting to know why these fail and if it is just a matter of time and mileage before this happens or is it a result of hard driving, faults in the shaft, shaft bearing failures or as with the RMS, alignment problems in some cases.

If it is a known mechanical problem is it possible to have it fixed before it detonates.

Porsche in Australia have a policy of supplying a replacement engine for I.S. failures at the bargain price of A$27,000 [uS$22000] !!!!!

Lots of questions here but it would be good information for those of us that are owners of early 996's if anyone has the answers.

Thanks.

[White987S]

I think IMS failure is far less common than RMS failure. Just much more painfull and expensive. :angry:

[rattles]

I agree not as common as RMS but on the 1st page of topics today there is one maybe two reports of I.S problems. My friends 99 996 died about a year ago and needed the replacement engine and I have heard about many others here and on the forum.

For such a major and expensive failure I was curious to know why they fail and if there was some sort of fix that could be done before they do.

[Tool Pants]

There is a ball bearing on the back of the engine case. The bearing fails and the shaft is no longer supported. First pic is a 1999 996 C2 with an intact bearing and no problem, and the second is a 2003 Boxster 2.7 with a failed bearing. The balls were literally falling out of the bearing.

This is why the first place to look is in the oil filter - to see if metal silver bits from a failed bearing have been trapped by the filter

[juniinc]

in my opinion ,doesn't really matter if your car is driven hard or babied.

If the car sits for a long period of time then risk can be high,,,

http://www.renntech.org/forums/index.php?s...9981&hl=IMS

[rattles]

There is a ball bearing on the back of the engine case. The bearing fails and the shaft is no longer supported. First pic is a 1999 996 with no problem, and the second is a 2003 Boxster with a failed bearing.

Thanks both for the info. and also the link, I searched for IS not IMS so missed that post.

[996TOULOUSE]

IMS Failures,

I had the IMS fail on my '99 996 just 3 days after I bought it with 80K Kms on the clock ! Since then I have done a lot of research and concluded that cars that have spent long periods inactive are much more prone to this failure. For sure the original design is weak - that's why Porsche have changed it several times over the years, but long periods of inactivity are not good for an engine.

I guess the advise is 'drive it every day' ! That's what I do.

'99 996 C2 Coupé

[rattles]

IMS Failures,

I had the IMS fail on my '99 996 just 3 days after I bought it with 80K Kms on the clock ! Since then I have done a lot of research and concluded that cars that have spent long periods inactive are much more prone to this failure. For sure the original design is weak - that's why Porsche have changed it several times over the years, but long periods of inactivity are not good for an engine.

I guess the advise is 'drive it every day' ! That's what I do.

'99 996 C2 Coupé

Thanks, mine does not get used that often but my friends car that did fail is used every day to get to and from work and has not been tracked. The bearing in the shots that Tool Pants posted looks large enough to do the job but maybe the shaft does not have enough support at other points or there is a lubrication problem for the bearing.

Mine is still going OK so fingers crossed, I was just interested to find out why they were failing and if there had been a fix from Porsche since then.

[Tool Pants]

I can't see how you drive the car having anythng to do with the failure of the intermediate shaft bearing. It is a rotational beaing that permits the shaft to spin. The shaft need to spin in order to operate the camshafts and oil pump. This claim is internet talk, and the same thing is said on the internet about the RMS.

I have been told by Peter Smith and another mechanic that Porsche went from a double to a single ball bearing in 2001. That is the same year Porsche changed the intermediate shaft. That is the year Porsche went from a roller type chain to a tooth type chain. I started Boxstering in 1999 and do not remember intermediate shaft faiures. That happened later.

Next time someone reports a confirmed intermediate shaft failure then make note of the model year and if it is the original engine. I am not claiming that pre-2001 is immune from an intermediated shaft failure.

The other factor in my lay understanding is that the bearing is sealed. If you look at my first picture you can see the black seal. That bearing is exposed to engine oil so I do not know why a sealed bearing is used. This has been noted by Baz Hartech. http://www.pistonheads.com/gassing/topic.a...Shaft%20Warning Hartech also notes that this type of sealed bearing is typically used in a transmission.

I have a Toyota truck and I am on some technical boards. Toyota uses sealed/shielded bearings in some transmissions. This bearing is exposed to gear oil, so why is it sealed? People who rebuild their Toyota transmission and replace a sealed bearing are warned not to remove the seal/shield, or the bearing will not last as long. Hartech on the other hand implies the seals should be removed for a Porsche M96 motor to improve lubrication.

This is an example of a sealed bearing from my truck. This the pilot bearing for the transmission. It is inside the flywheel. It is not exposed to any type of oil, but relies upon grease inside the seals for lubrication of the bearing for the life of the bearing.

[Dscott]

So is it reasonable to simply replace this bearing; like when dealing with the RMS?

[whw7]

Is there any difference between Tiptronic and Manual when it comes to IMS problems. Possibly less shock and awe on the engine?

[rattles]

I can't see how you drive the car having anythng to do with the failure of the intermediate shaft bearing. It is a rotational beaing that permits the shaft to spin. The shaft need to spin in order to operate the camshafts and oil pump. This claim is internet talk, and the same thing is said on the internet about the RMS.

I have been told by Peter Smith and another mechanic that Porsche went from a double to a single ball bearing in 2001. That is the same year Porsche changed the intermediate shaft. That is the year Porsche went from a roller type chain to a tooth type chain. I started Boxstering in 1999 and do not remember intermediate shaft faiures. That happened later.

Next time someone reports a confirmed intermediate shaft failure then make note of the model year and if it is the original engine. I am not claiming that pre-2001 is immune from an intermediated shaft failure.

The other factor in my lay understanding is that the bearing is sealed. If you look at my first picture you can see the black seal. That bearing is exposed to engine oil so I do not know why a sealed bearing is used. This has been noted by Baz Hartech. http://www.pistonheads.com/gassing/topic.a...Shaft%20Warning Hartech also notes that this type of sealed bearing is typically used in a transmission.

I have a Toyota truck and I am on some technical boards. Toyota uses sealed/shielded bearings in some transmissions. This bearing is exposed to gear oil, so why is it sealed? People who rebuild their Toyota transmission and replace a sealed bearing are warned not to remove the seal/shield, or the bearing will not last as long. Hartech on the other hand implies the seals should be removed for a Porsche M96 motor to improve lubrication.

This is an example of a sealed bearing from my truck. This the pilot bearing for the transmission. It is inside the flywheel. It is not exposed to any type of oil, but relies upon grease inside the seals for lubrication of the bearing for the life of the bearing.

Thanks for the detailed reply and the link to Hartech's post. The car I mentioned that had the IMS problem was a 1999 model so early cars are not immune. When you consider the various points raised it seems to point to either an alignment or stress problem or maybe just poor quality bearings. I have found enough low quality parts in my 99 model to make me question ''Porsche quality'' so maybe they were cutting costs on the IMS bearings as well.

[1schoir]

Thanks for the detailed reply and the link to Hartech's post. The car I mentioned that had the IMS problem was a 1999 model so early cars are not immune. When you consider the various points raised it seems to point to either an alignment or stress problem or maybe just poor quality bearings. I have found enough low quality parts in my 99 model to make me question ''Porsche quality'' so maybe they were cutting costs on the IMS bearings as well.

It's depressing to think that Porsche would cut costs on a relatively inexpensive internal part of the engine.

Regards, Maurice.

[1999Porsche911]

I think it would be more informative to find out what oil is used in the engines that experience problems like this. The full history of oil use and not just the current brand and weight. IMO, anyone who is worried about failures like bearings and continues to use Mobil's 0W40 or equally inferior oil, is justified in their concerns.

Why some people insist on running the weakest of the oils on the approved list makes no sense to me.

Edited September 23, 2008 by 1999Porsche911

[eDoug]

IMO, anyone who is worried about failures like bearings and continues to use Mobil's 0W40 or equally inferior oil, is justified in their concerns.

My IMS failed with M1 20w-50.

Why some people insist on running the weakest of the oils on the approved list makes no sense to me.

"Weakest" oil? My opinion is that the 0w-40 is probably better for the tight tolerances of these engines. But this is pure conjecture, isn't it? I'm no expert... so I won't pretend to be either.

[White987S]

I think it would be more informative to find out what oil is used in the engines that experience problems like this. The full history of oil use and not just the current brand and weight. IMO, anyone who is worried about failures like bearings and continues to use Mobil's 0W40 or equally inferior oil, is justified in their concerns.

Why some people insist on running the weakest of the oils on the approved list makes no sense to me.

I might agree with some if this. I use Red Line 5W40 in my car. Love it.

I would also like to see some correlation between IMS failure and proper engine brake-in when the car was spanking brand new. I realize this may be impossible to gather. Just another thought.

[eDoug]

I would also like to see some correlation between IMS failure and proper engine brake-in when the car was spanking brand new. I realize this may be impossible to gather. Just another thought.

I wondered about break-in as I just finished my 2,000 miles on the new (reman) engine. I kept it under 4.2k for most of the break-in, generally keeping less than 50% throttle most of the time. I ran it up to the 5k range in the last few hundred miles, and have just started shifting occasionally above 6k... I don't plan to bump the limiter or approach it - I think >6.5k rpms probably provides diminishing power/performance/wear returns.

From the mechanics I've spoken to about the IMS failure, general concensus is that "it just happens." As an engineer, I'd like to disagree with that notion and think everything happens for a reason. But there are far too many complexities involved and not enough hard evidence to support all the conjecture... except maybe the evidence in Porsche's hands. My approach with the new powerplant will be to keep using Mobile "water" or perhaps use a good 5w-40 product. Never run it above 3k when cold (H2O temp >180), or over 4k until the engine is good and hot (>15 minutes driving).

What else can you do??? Everyone has their own ideas - but as for me - I figure you just have to drive 'em like they were meant to be driven: run it often, and run it hard but not abusively.

It doesn't hurt to keep a piggy bank nearby to save up for the worst.

:o

[gandrade1]

I think it would be more informative to find out what oil is used in the engines that experience problems like this. The full history of oil use and not just the current brand and weight. IMO, anyone who is worried about failures like bearings and continues to use Mobil's 0W40 or equally inferior oil, is justified in their concerns.

Why some people insist on running the weakest of the oils on the approved list makes no sense to me.

What is a good oil then? Brand/viscosity ?

Thanks,

Gus

[White987S]

What is a good oil then? Brand/viscosity ?

Thanks,

Gus

Gus, as a contributing member, you have access to the TSB's and in there is a very comp. list of Porsche Approved Oils. Just pick one you like most.

[rattles]

IMO, anyone who is worried about failures like bearings and continues to use Mobil's 0W40 or equally inferior oil, is justified in their concerns.

My IMS failed with M1 20w-50.

Why some people insist on running the weakest of the oils on the approved list makes no sense to me.

"Weakest" oil? My opinion is that the 0w-40 is probably better for the tight tolerances of these engines. But this is pure conjecture, isn't it? I'm no expert... so I won't pretend to be either.

The photos that Tool Pants posted show that the IMS bearing is sealed and has its own lubrication built in so the type of engine oil used should not have an effect on that bearing. I'm no expert either but if a sealed bearing fails makes me think it's either poor quality or it's been overloaded in some way.

Most of the reports that I have read say the IMS failure is immediate, you dont get any warning. Compare that with other ball bearing problems in cars or machinery, usually the faulty bearing will continue to work for a while but gradually gets noisier.

[eDoug]

Most of the reports that I have read say the IMS failure is immediate, you dont get any warning. Compare that with other ball bearing problems in cars or machinery, usually the faulty bearing will continue to work for a while but gradually gets noisier.

From first-hand experience - the "IMS Death Rattle" is not uncommon. I thought it was a water pump, then maybe a belt tensioner/pulley, then it just let loose and dumped 9 qts of M1 20w-50 on the garage floor. The rattle was probably present from the first time I noticed it, until it worsened over the course of 200-300 miles in a week - then it failed.

Edited September 25, 2008 by eDoug

[c70Pete]

Most of the reports that I have read say the IMS failure is immediate, you dont get any warning. Compare that with other ball bearing problems in cars or machinery, usually the faulty bearing will continue to work for a while but gradually gets noisier.

From first-hand experience - the "IMS Death Rattle" is not uncommon. I thought it was a water pump, then maybe a belt tensioner/pulley, then it just let loose and dumped 9 qts of M1 20w-50 on the garage floor. The rattle was probably present from the first time I noticed it, until it worsened over the course of 200-300 miles in a week - then it failed.

Hey Doug,

what exactly did the rattle sound like....? we have a 996 that is making a loud ticking that seems to be coming form the right rear of the car... and it gets faster as the RPM's go higher and doesn't want to go away... is this what your car sounded like?

P.

[togilvie]

deleted

Edited March 29, 2012 by togilvie

[Dharn55]

Togivlie - Where did you get your rebuilt engine. When I googled Strausse I got Strausse USA in costa Mesa and they said they don't rebuild engines, they only use OEM remans.

[c70Pete]

Now, a few weeks preceding this event, an intermittent, muffled clanking noise (hmm... like a nylon screw rattling around in a coffee can?) could be heard when inspecting an idling engine. It was sometimes difficult to hear, and sometimes the noise would cease for periods longer than a day. I do not hear this noise on my rebuilt engine, so perhaps this was the indicator. I monitored (but somewhat disregarded) this noise because it is often trumped by my ticking lifters, automatic fans, etc.

ADVICE: if you hear a similar sound, don't hesitate to take the car to an indie and inquire about this problem and preventive remedies, but note that this clanking is intermittent and is not the same as the periodic ticking noise often encountered in an old hydraulic lifter.

so it was a rattle and not a ticking.... and it did not increase in frequency i.e faster rattling or more tapping as the engine revs increased? hmmm... maybe we have a bad lifter instead?