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The IMS discussion thread (Read this first!)

Old 09-12-2010, 07:44 PM
Marc Gelefsky
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Default The IMS discussion thread (Read this first!)

Use the search feature before you ask a question, There is a ton of information to be found!
If you do not find what you are looking for, by all means post your question!


This thread is for the discussion of IMS related questions and issues, new threads on this topic may be merged here.

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Old 02-06-2011, 08:53 PM
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RMS and IMS what is it? Lets start with the easier one RMS

RMS= Rear Main Seal. This is a seal that seals the crank. It is known to leak oil. It is located on the rear of the engine (but towards the front of the car, the front of our engines face the rear of the car. So when you open the rear hatch, you are looking at the front of the engine). To get to the seal you must drop the tranny, flywheel, clutch (if not a TIP) to expose the seal. Most times the seal is $20 bucks but takes anywhere from 5-10 hours to replace pending the technicians skills.

Why does it leak? We have two issues that I know of. First and easiest is the original seals were not that great. They were too hard and would actually wear a low spot in the crank allowing oil to pass between the seal and crank. The new seal has quite a bit of changes and has a much softer, almost cloth-like material where it contacts the crank. You can see the difference.

Possible issue #2 is the crank actually being off center. Yes… I know.. WHAT? Yep… Some how some engines wore in and the crank is actually off center. This will cause a leak and if you just put in a new seal it too will leak. Let alone the pre-mature engine failure you may get from the additional wear from vibration. Porsche basically replaced any engines with this issue if they were under warranty. This issue can be fixed by an after market company. To test of the off center crank isn’t hard, it just requires a dial caliper and the know how to use it. I do not know the exact tolerance of wobble.

Special Tools to replace RMS. No special tool are really needed that cannot be home made from common parts found a Lowes. If you do a search on the forum you will find some home made tools to complete the job.

Next is the biggie. IMS… stands for Inter Mediate Shaft. This is a shaft that is located below the crank. It is gear driven off the crank, the IMS then in turn drives the chains that drive the cams that open and close the valves. The part that fails is not the shaft but a bearing on the rear end of the shaft. In the simplest terms the valve train then jumps time and the pistons collide with the valves, many times breaking the piston, then breaking the cylinder/block. Basically when this happen the engine is pretty much done.

What are the warnings signs? You ready for this.. VERY FEW and they are not obvious. I have been told that when it goes, it goes fast. A common explanation is “it sounded like marbles rolling around in a tin coffee can right before it quit” This noise is the shaft bouncing around after the bearing has failed. You have seconds to shut the engine down and hopefully save it. Another clue to pending failure is an oil leak. But the bad thing is the leak is at the exact same location as a RMS leak because the IMS is located right below the RMS… But many times there is a difference. An IMS leak GENERALLY will spew black, burnt oil while an RMS leak will spew caramel color oil.

So what can be done? The RMS is easy. Install the new seal. The IMS is a crapshoot… Many have chosen to install a ceramic bearing; this bearing can be installed with out tearing down the engine. It requires a special bearing puller. I did mine myself on my garage floor. I think it took me 10-12 hours.

What is Porsche doing? Nothing…they are following the law and if you car is still under warranty, you get a new engine.. No hassle, no crying. They fix it. If you are out of warranty… Don’t bother. They will not do much to help you. You can threaten to sue. You can sue… you can cry, you can beg… You will get nowhere. NO WHERE.. Trust me on this one… Don’t even frustraight yourself. But if you are under warranty. They will not give you any hassle at all… The new engines are upgraded. I am not sure what the upgrade is… But they are different.
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Old 03-05-2013, 01:31 PM
AZ Erik
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Default IMS... here's a thought

Whoever ends up making this part (if it's not me) can pay me royalties of the 10's of parts to be sold.

IMS Bearing failures appear to me to be due to engine oil compromising the sealed bearing and forcing the thicker viscosity lube out (somewhere).

The IMS bearing 'rides' in a tube, which for some reason the other end is near the RMS. The RMS leaks, fills the tube with oil, pushes out the lube, nukes the bearing.

Oil doesn't need to be in that tube, actually it's better (saves your *** really) if there isn't oil in the tube to get to the bearing.

Why hasn't anyone made a simple friggin 'oil plug'! Piece of rubber with a whol through it, a bolt, a nut 2 washers and a foot long extension to tighten the bolt/nut., Snug enough to block or mostly limit the amount of oil getting into the tube.

Every IMS bearing story I have read so far has oil in the tube. Stop the oil and the bearing might just last the entire engine life (which oddly can be limited by this bearing failing so it's all still true )

If I get a 996 or have to do a IMS replacement on any pcar, this is on my list of todo's. Does this already exist?

Last edited by AZ Erik; 03-05-2013 at 02:50 PM.
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Old 03-05-2013, 07:32 PM
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what kind of oil are you using? ....IBTL...
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Old 03-06-2013, 09:14 AM
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thermal expansion of the trapped air causes air to escape, when the parts cool there is low pressure in the tube, the low pressure is equalized by air and oil being sucked into the tube

each cycle there is more oil and less air

the oil in the tube is contaminated and can, over time become toxic enough to erode, etch the ***** on the bearing - the softend ***** wear faster, and become rough. the rough ***** catch on the ball cage and begine to distort the holes that hold the ***** in place - the holes become large enough for the ***** to bounce around and bend the cage, the cage slips, the ***** change location and the bearing comes apart - the bolt cannot support the rotational out of balance and shears off - the chains jump and - whip around, vale timing stops and the pistons collide - failed parts cause case damage and oil is dumped out of the damaged area...

I am theorizing of course - but I have detailed photos of bearing in various stages of degradation and under magnification I would place money on chemical etching being the initial cause of surface breakdown

yes - a 1 mm hole drilled in the tube may prevent all of this
yes - replacing the bearing is a good idea
yes - they can fail - and failure is a biatch
yes - many last a LONG time

why would running them "like you stole it" help?
my theory is that it is a means of getting the car over the normal operating temp and thus pushing some of the old contaminated oil out of the tube...and sucking in some new oil - at some point if temps never exceed a "normal" the oil in the tube never comes out and could be in there for 5-10 years no matter how often you change oil. You have to get the motor hotter and cause the old oil to then exit thought hydraulic pressure and re-create the vacuum that cause the oil to be sucked in there in the first place...this will also allow "fresh" oil to be sucked passed (through) the bearing and give it a tiny bit of lube internally


these are thoughts I have - and my personal research was supportive of this crack induced dream
I hated that this thread was made with the statement above and never allowed to be argued, I am glad it is open for discussion - I will not be discussing it much, I prefer to just replace the damn thing and get over it, live with it and run the "risk" - or sell the car

I sold mine - but not because of was time for me...... I miss it sometimes, but I would NOT trade my current ride for a 996 unless it had 3 letters after the 996 --- something like GT(x)

have fun with this, hope to see some of you around at PCA or other events in the great northwest
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Old 03-06-2013, 02:36 PM
AZ Erik
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My thought being if the factory put in a sealed bearing, and all but the $1500+ LN retrofit also use sealed bearings why allow oil in the first place.

The drilling of the hole is actually a great idea. (Me theorizing as well) If one could drill the hole say 3 inches past the IMSB, this would allow about 2 of inches of 'workspace' to put in a plug. Any and all oil that found it's way into the tube would fall out the bottom, keeping it clean and away from the bearing. It would also alleviate the tube pressure equalization that causes the oil to be sucked in (in theory). I' figure the factory sealed bearing probably had a service life of over 100K at specific loads, if it remained in it's sealed little form.

That said my Roomba also has sealed bearings that should "last 5 years" that lasted all of 6 months.
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Old 04-11-2013, 10:26 AM
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Drive it like you stole it..... someone said. Well, I had a chance to speak with one of Porsche's most respected authorities & race mechanics regarding the 996 RMS & IMS issues. He stated the main issue for these failures are because people are not driving the cars "hard" enough. Usually the driver is too low in the rpms (below 3.5K rpm) when they step on the gas which creates huge stress & pressure. He states driving this car in the city in 5 gear is the a serious issue. In all the years the 996 motors were raced he recalls it had the least number issues or failures... he states it was a very strong motor ever. Keep the rpms higher in the city. When on the hwy 5th & 6th is ok because the speed is constant and little demand but don't slam the gas in 5th or 6th to pass, play in the 4.5K to 6K range. Ps. you won't need PSE now either! Hope this helps.
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Old 07-29-2013, 05:13 PM
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Has anyone done the new ims solution with the oil fitting and no ball bearings???
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Old 08-21-2013, 07:46 AM
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Default hi all very heavy rattle

Hi all im new on here and ive had my 996 c2 coupe for about 10 months now,
It has now developed a heavy rattle a very heavy rattle from the engine the only way I can explain what it sounds like is if someone put a brick inside a moving cement mixer....bang rattle crack etc......
Anyway ims is the suspected cause but my question is,
Is it possible for me to get away with just a ims bearing replacement or is it a strip down of the engine regardless ???
The car wasn't driven since the noise started only very short distance to get her home.
I just cant find a answer anywhere online for my question.
I understand all cases are different but has anyone had a heavy noise and got away with only bearing replacement??

P.S great site!!!!!!
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Old 09-03-2013, 04:06 AM
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oops never mind wrong forum

Last edited by Orion03; 09-03-2013 at 04:09 AM. Reason: wrong forum
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Old 09-28-2013, 10:50 AM
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996 owners beware, if you do not already know Autoweek recently had an editorial that ripped the 996 and Boxster. The cars have had some issues no doubt, but are still fantastic.Mine has given me very little trouble, I can drive to the track use it hard all weekend and drive home in comfort with the a/c on and have no worries. This article is going to hurt the cars resale and reputation.
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Old 09-28-2013, 11:03 AM
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Default IMS Porsche Settlement Class Action Lawsuit

My fellow Porsche lovers for those of you that have IMS issues with your 996 see link
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Old 10-04-2013, 12:16 PM
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I doubt it will affect 996 resale. It is 10 year old news now and the 996 already took the hit. In fact their prices have bumped up a bit in the past year.
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Old 10-18-2013, 11:54 AM
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Since the Class Action was against PCNA, does anyone have any idea why there are ROW cars amongst the list of affected VIN numbers?
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Old 11-19-2013, 10:57 PM
Zanzibar Red 996
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Maybe it's time to do a updated list of the several
Different approaches to
remedying this problem
Which have been presented
since this discussion began.
The most recent attempt is
called "DOF"
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