Rear Main Seal ?

In my hunt I came across a 2002 with 84K miles. Looks clean and has pretty comprehensive records. The Carfax shows it was originally a lease and has always been serviced by a Porsche dealer. The Carfax does show that the RMS was replaced 4 times within the first 20K miles. My question is, why would the RMS leak so often? Is this indicative of a bigger issue, or is it a case of the dealer not doing the work correctly? Otherwise the car looks to have been well maintained.

The original RMS was a POS. The revised seal fixed many of the cars that were habitual leakers. A car with a leaky RMS does not necessarily indicate any other issues; in fact, some people just gave up on the RMS and live with the leak, since it's not exactly trivial to access the RMS.

Check the serial number on the motor to see if it has been replaced. SOP back then was if the RMS leaked 3 times under warranty Porsche replaced the motor (3rd RMS was the charm on our 2001). As I understand it there were 2 cases. The first was that the seal was bad or not installed correctly and the second was a machining defect in the case. In the later case there was nothing you could do as any seal was going to fail. With Jake's revelations about machining issues around the IMS, I wonder if the two aren't related actually... The upside is that most RMS leaks were found early on while warranties were in effect. Now we are seeing them fail simply due to age and milage. If it's last RMS change was 64k+ ago, I wouldn't worry about it unless your PPI finds signs of it leaking.

Do you have a link?

Here's the Carfax info. Four times in 24K miles, not 20, but no mention of a new motor. 03/18/2003 13,886 Sonnen Porsche Mill Valley, CA [phone removed] 15,000 mile service performed Airbag system checked Interior trim checked Rear crankshaft oil seal replaced Tire condition and pressure checked 05/29/2003 15,323 Sonnen Porsche Mill Valley, CA [phone removed] Vehicle serviced 07/01/2003 16,410 Sonnen Porsche Mill Valley, CA [phone removed] Airbag system checked Coolant reservoir replaced Cooling system checked Drivability/performance checked Rear crankshaft oil seal replaced Wipers/washers checked 07/29/2003 Sonnen Porsche Mill Valley, CA [phone removed] Body side molding(s) replaced Exterior trim checked 09/02/2003 17,112 Sonnen Porsche Mill Valley, CA [phone removed] Interior trim checked 09/26/2003 17,125 Sonnen Porsche Mill Valley, CA [phone removed] Reverse light switch replaced 03/18/2004 22,411 Sonnen Porsche Mill Valley, CA [phone removed] Pre-delivery inspection completed Airbag system checked Computer module replaced Rear crankshaft oil seal replaced Safety inspection performed Tire condition and pressure checked Tire(s) replaced 03/19/2004 22,415 California Inspection Station Passed emissions inspection Owner 2 Purchased: 2004 Type: Personal Where: California Est. miles/year: 4,901/yr Est. length owned: 3/20/04 - 2/26/11 (6 yrs. 11 mo.) Low mileage! This owner drove less than the industry average of 15,000 miles per year. Date: Mileage: Source: Comments: 03/20/2004 22,431 California Motor Vehicle Dept. San Francisco, CA Title issued or updated New owner reported Loan or lien reported 08/11/2004 24,747 Sonnen Porsche Mill Valley, CA [phone removed] Airbag system checked Brakes checked Clutch checked Engine checked Engine oil/fluid leak checked Interior trim checked Rear crankshaft oil seal replaced

I say you don't have much to worry about the RMS seal, 20K was a long time ago! Just curious, is this a cab?

No, it's a coupe.

If you check the "Blown Engine" thread you will see an explanation of why the depth placement of the Rea Main Seal is critical but over a surprisingly large acceptable range. Renntech has the best detail on making an effective diy tool to control the depth. If the c/s has a wear mark on it ,a different strategy is required. Ignore any/all of this & more leaks are likely.

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My recollection is -- and this lines up with what gnat had to say -- if an engine exhibits a chronic RMS leak this can be a sign the crankshaft journal to RMS bore is not concentric. But it has been since mid-2002 at least when the RMS in my Boxster engine was replaced for a dealer tech to check the concentricity of the crankshaft journal to RMS bore and if this is found out of spec to replace the engine. The RMS will never stay oil tight and often the engine fails. (Porsche even made a special go/no go gage a tech could use for this. Early on the tech had to check this manually with an inside micrometer.) Another thing is it was SOP even back in mid-2002 to when replacing the RMS to replace the original IMS end flange and its original bolts with new/improved hardware. There was no way to distinguish between an RMS leak, an RMS/IMS end flange/bolt leak, or just an IMS end flange/bolt leak. So both the RMS and IMS end flange and its bolts were replaced. The new IMS end flange has 3-ribbed seal (vs. the single o-ring of the old flange) and the 3 bolts are micro-encapsulated to seal the bolts as they thread into an area which can be under water, err oil. (This was done on my Boxster in mid-2002 and at around 25K miles. Now with over 307K miles the RMS and IMS flange/bolts are still oil tight.) I note in the services listed there was no mentioned of the IMS flange being replaced. If you elect to have the RMS replaced again the tech must/should check the concentricity of the crankshaft journal to the RMS bore in the block. If this is found acceptable he must install the new RMS so its seal rides on a virgin area of the crankshaft journal. As the engine runs the previous seals wore a groove in the journal. If the new seal is installed at one of these positions it will leak. Last but not least the IMS end flange and its bolts should be replaced.

That's some great info! Thanks guys. I'm going to take a look at another car next Tuesday that hasn't had any such issues reported on Carfax. If it looks clean enough I'll get a PPI done and go from there.

Macster, by the 2002 MY they should have all had the new flange/seal on the IMSB right? Our 01 never had its flange replaced, but it was a triple rib on a dual row bearing.

Yes...Mr. Gnat...?

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I haven't found a specific date for the change to the updated RMS (not IMS), but Pelican states: "The seal has been updated to a 997 "Cayenne-style" part number since the engine was originally introduced, and for the most part the engines no longer leak from this area when this new and improved seal is installed."

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Macster mentioned not seeing a line item for the IMSB flange/seal being replaced which was protocol for any older style flange/seal the first time the dealer pulled the transmission.

Does Macster have the highest mileage Boxter on the forums at 307K miles?? Impressive.

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Maybe. Maybe not. According to some reliable sources what parts were used is not consistent. Some engines could have ended up with the older style end flange seal. FWIW, My "2002" Boxster was built in late 2001 and I believe has the single row bearing based on the end flange but even that is not a given. As one reliable source says, in so many words, you can't really know what's there until you look. There is also the the possibility the end flange is replaced as a preventative measure regardless of whether it has the new seal or the old seal. My car was in for a RMS leak under warranty. From Porsche's point of view the extra part and labor cost of replacing the end flange even if it may not be leaking and even if it is of the newer style is preferrable to even greater extra part and labor cost of having to drop the transmission again and replace the IMS end flange and bolts should the owner bring the car back with an "RMS" leak. The new RMS of course could be leaking so a good 2nd repair (if anything was learned from the 1st not so good repair) would replace this as well. Far and away then the best course of action would be when the car is in for a RMS leak both the RMS and the IMS end flange and bolts are or should be replaced regardless if the end flange is the old style or new style.

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During my trips around the western half of the country I've encountered reports of other high mileage (~300K or more) Boxsters. One report I recall has the car in the southern MO area and is reportedly a 2.5l car with its original clutch. The Springfield MO Porsche dealer SM told me of this car when I was there back in Jan. 2015.

The rear main “seal” is not the problem causing the leaks. The problem is the crankshaft design and consequently the lack of bearing support, chain drive forces, and the weight of the OEM flywheel causing the RMS to leak. Once the crankshaft is checked to assure it is not out of round, you should consider getting the permanent RMS upgrade available at Vertex. They have created the bearing support that eliminates future RMS leaks and reinforces crankshaft support. I had them install this in my 1999 996 and am thrilled. The engine feels more solid and sounds (better) different.

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Do you have a link to this upgrade? I ask because the Vertex RMS page has no mention of this part: https://www.vertexauto.com/porsche-r...r%20mai%20seal And at least one expert (not me)disputes the need/use/value of such a part. #22 -here: https://rennlist.com/forums/996-foru...in-seal-2.html

Balanced or unbalanced DMF impact the crankshaft, it's the weight. I contacted Gilbert at Vertex and he stated that since the product is new they haven't uploaded the information to their website. Being the Holidays he did not give a definitive date about publishing the information at their website.

Interesting idea .If it is necessary, surprising that LN,Jake Raby, Hartech and others never have mentioned developing such a product. There have been other Threads where there has been comment on the huge amount of weight that the rearmost bearing supports because the DMF+clutch assy.weighs 50 pounds. So it is all the more surprising that an upgrade was not developed - until now. At 30pounds, an unbalanced DMF (and many are unbalanced) is a problem that is easily & inexpensively rectified during a rebuild & when fitting this new , reinforced bearing carrier. The other problem is that the DMF is huge heat sink/source for that bearing and the gearbox.

No reason for this "product". Its a band aid for a machining issue from the factory. There's plenty of bearing support. The crank carrier is held in place by two 11mm dowel pins, and also all 24 cylinder head bolts, which thread into it, providing clamping load. It takes more than a 50 pound flywheel assembly to create a problem with this. That as BS created by marketing from those trying to sell a junk lightweight flywheel 15 years ago. The cases where the RMS issues exist were factory mis- machined. I spend my time developing things that are really necessary.

The RMS Fix does not address any issues related to the crank carrier. Instead it directly resolves the crank shaft design problem; the last bearing and the load forces present. Specifically the root cause of the issue with the RMS leak, a design flaw which comes from a combination of a heavy flywheel, the length or load point from the fulcrum lever of the last bearing, the chain (which is placed on this end, unlike the air-cooled crank chain), and the small bearing surface area of bearing number 7. The OEM DM flywheel is heavy and the distance of this 30lb mass from bearing cause excessive rotational radial forces along with the additional load from the IMS chain cause excessive forces on the crankshaft. This combination of design and forces cause premature wear on bearing 7, and under extreme conditions failure. Take a look at the pictures below. The picture on the top shows the bearings found in the M96 (left) and the bearings found in the air-cooled (right). In addition to the size difference there are twice as many lubrication ports. The next picture shows the end of the crankshaft for both the air and M96 engines. With the bearings in place, you’ll see chain gears and the crankshaft end at flywheel. The bearing of the air-cooled sits near the edge of the crankshaft, while the M96 has chain gears beyond the bearing or fulcrum point. Check out the difference in size between the bearings. The air cooled has 30mm of surface area to handle the loads while the M96 bearing has 12mm of surface area. That’s 2 � times smaller surface area to handle an even greater load capacity difference! Imagine the forces on that small bearing, the forces from the IMS chain, and the forces from the flywheel. The first symptom is a vibration to the crank which causes improper sealing of the rear main seal. When the problem gets more severe, there is a twisting or bending of the last crank journal which then provokes the lubrication failure to the last journal and consequently the lack of lubrication to cylinder number 6 rod bearing which is lubricated via the last main bearing number 7. When bearing number 7 is expanded or out of tolerance due to the vibration and twisting of the crankshaft, then the oil pressure will not reach the number 6 rod journal and ultimately fail. The vibration and twisting of the crankshaft on the last bearing causes main bearing number 7 to expand and wear out, or lose its tolerance and then fail to lubricate rod number 6. This problem is caused by the fulcrum distance, the heavy flywheel the additional chain load and the small bearing surface area. The loads that are present are greater than what the last bearing is capable of carrying and theses forces cause premature failure. Check out the picture below that shows the RMS Fix as an additional bearing “Number 8” at the proper point to eliminate the fulcrum lever and increase the last bearing’s surface area to provide proper support. The unsupported excessive weight at the end of the crankshaft is now supported by this new Number 8 bearing with the old bearing. This new Number 8 bearing consequently eliminates rear main bearing seal oil leaks, reduces engine vibration, increases the life of bearing number 7, eliminates the risk of rod bearing number 6 failure from lack of lubrication and most important reduces the consumers’ running costs for maintenance and total engine failure. We are working on adding this information to our website, if you would like even more details, please contact Vertex.

These two cannot be compared. The statement that was made failed to note the differences in crankshaft deign between the two engines. The aircooled engine uses the rear main not only for radial support of the crankshaft; but, also for longitudinal crankshaft support. The M96 does not do this, as it adjusts longitudinal end play, and carries those thrust loads at the center main position of the crankshaft. This changes everything. With thrust control being handled by the center main, via a pair of thrust shims, the task of longitudinal thrust control is removed from the rear main bearing altogether. These are the details that people need to understand concerning the design differences between the two engines, and why this comparison is like comparing apples to grapefruits. The reason these engines lose #6 main bearings (on track) comes from heat saturated through the clutch, that is transmitted through the flywheel (another reason an aluminum flywheel is a bad idea) and then into the crankshaft, impacting the rear main bearing. This creates oil shear, leading to wear- metal generation, which then floods the #6 rod bearing with debris laden, centrifugally delivered oil, which then takes out the #6 main bearing. If indeed the new "number 8 main bearing" is intended to carry load, how is this unit lubricated with oil from the primary oil system?

Rod, Details make the Engineer. Your post reads: "the M96 (left) and the bearings found in the air-cooled (right). " Actually ,the opposite is what you mean ?If so, suggest you fix it I am encouraging you because anything that improves the M96 is welcome. Your explanation is plausible . Suggest you need to work on the rest of the story. 1. If the larger bearing solves the problem, you have test results for that right ? 2. These results would show a substantial reduction in flex and vibration at different sustained engine speeds on a test rig. 3.The same test results would show a reduction in heat in the proximity of the new bearing also. 4.You have comparitive data from 2 identical engines with balanced DMF- 1 with the new bearing ,the other with the stock bearing ?? Without such test results your product is merely an intriguing diy project.I agree ,it would probably do no harm but let's try a more ambitious goal than that? Test data would quickly neutralize most of the dismissive comments from us. All that would remain to validate your product would be long term field/race testing. Without the rigor of debate and testing this is interesting idea is doomed - like grooved oil pump drive shafts and DOF. Let's avoid that? I hope you can continue to develop this idea successfully.We need every upgrade we can get for the M96.

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At minimum. Don't forget UOA before and after to see how that added material effects wear metal levels. Or material type, you can't just expect some scrap piece of 6061 to handle this load, (as a random example) and I'd expect a lot of the same issues with material choice as what I went through for several years with the IMS Solution development. When adding a wear surface, friction can (and most of the times does) increase, so this should be indicative in UOA very clearly. In this region of the engine there's no primary oil pressure delivery, only splash oiling, hence my question about how a supply of fresh oil is supplied to the new bearing, to both cool, and lubricate it. I am always trying to make the machine simpler, by removing parts, and wear surfaces, so hopefully Rod can shed some light on this.

I hope Rod appreciates the value of the advice you are giving.

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Well, I typically charge a lot for that, like 350 bucks an hour.... Isn't this forum a wonderful thing?!

At least the rest of us usually say "Thank you" :-)

I sure do appreciate the pro's that chime in...Thank you!