IMS center bolt
 

I am about to rr my clutch,RMS and ims. I am making my tooling and my question is does anyone know the thread and size of the center bolt on the original? I need to get the correct coupling nut for my puller.
Thanks, Dave

Mine had an M8 1.0 mm center bolt, it`s a 1999 Boxster. I wouldn`t waste an original dual row bearing at such a low mileage though by pulling it out. Just a thought.

Thanks appreciate the quick response. I’m changing it with low miles mostly due to the clutch..... which leads to the RMS. Which leads to the IMS. I would prefer to remove the inner seal on the IMS bearing but there’s no way to remove without pulling on the inner race which is fine to get it out but not to reuse. Too much stress/damage unseen to comfortably trust it after that. I see videos of guys “tapping” on the inner race driving it in that last 16th inch possibly damaging the bearing. This is done on the way out. I went back and forth on leaving it completely can’t go that either.......

Why remove the inner seal? I removed the outer seal to allow engine oil lubrication and other than that left the original bearing as it was. The car has been running for 2 years since with no problems.

I agree. Removing the inner seal wouldn`t make any further difference.

Wouldn't the oil flow from the inside outward? Keeping the inner seal in blocks the oil flow. Maybe not completely, but it surely restricts it.

The inner seal side of the bearing is in the IM shaft, so the only oil on that side is oil that has passed through the bearing and is trapped in the shaft. The good stuff is on the outside.
The PCA videos with Jake Raby explain in detail what is happening with the IMSB.

So a couple questions, the really crappy oil that comes out when the bearing is pulled is there because of the inner seal causing stagnation or in other words because the inner seal doesn’t allow the oil to flow thru the bearing? Does the Retrofit LN bearing have an inner seal or does it let the oil flow thru or rely on immersion and splash?
I appreciate you guys and your knowledge.........

The original bearing is sealed with grease filled inside. IMS is a tube with about a liter of air trapped inside, since both ends are closed. When the engine warms up, pressure rises within IMS, and after a while air will leak through the bearing`s seals, creating vacuum when the engine cools down and the pressure drops. Eventually this will cause the oil to seep into the IMS, and will fill it, since the entire shaft is submerged in oil. Since it does not circulate so well, and you can`t drain it when replacing engine oil, it will become darker and crappy than the rest of the oil in your engine. So, if you just remove the outer seal, the bearing will get sufficient lubrication from outside. Somewhat depending on the oil level in your crankcase, it will get direct oil from being submerged, from splash, plus oil mist.

As far as I know the retrofit has no seals.

Thank you Homeoboxster, to my surprise the retro kit showed up today and it has one seal, the inner. As of now I think I’m going to inspect in place removing the outer seal, if I have any doubts I’ll replace. I’m having no luck finding the m8 x 1.0 coupling nut for the puller. I contacted LN for a source and was told that they are going to start loaning tooling (2021) for free with purchase from them. I bought from Amazon so as far as tooling I’m SOL but the kit was $200 less expensive and according to Amazon returnable thru 1/31.
Thanks for the help and loan of your knowledge.

A wise course to take IMHO. If eventually you do want to change the bearing see the videos on Youtube by Ben Burner. He made or improvised all the tools necessary, for almost nothing.
https://www.youtube.com/watch?v=UJ5WwbgQejs
From there you can link to his complete series of IMS bearing replacement videos.

Tool kits are often offer in for sale forums.

Thanks Mike, I got the puller/tools figured out, bought the correct tap and drill bit from Amazon delivered next day. Bought a 1/4” coupling nut, drilled and rethreaded to m8x1.0, same for the puller rod..... and red loctited matching bolt in the rod.I’ll let you know

Just now that you spent so much time and effort on making a tool don`t feel obligated to use it ;)

I went in to my 23,250 mile 1998 Box and as the pictures show the dual row bearing was on its way. I pulled the seal on the bearing and found the bearing cage was broken but still in place and the balls just starting to go but races looked good.......there was surprisingly very little metal. When I pulled the bearing there was some in the tube but again very little, used paper towels on a set of magic fingers first with diesel fuel on the towel, I have a borescope and there is now nothing in the tube. I pulled the filter and it was spotless, dropped the oil and pan also spotless. The oil and filter had 500 miles. bought the car with 9100 miles in 2017. the oils been changed 4 times since I've had it with one being at the PDI. every filter has been cut and inspected with each. Did a 5000 mile cross country trip last July and changed the oil before I left and when I got home and inspected that filter as well, all have been spotless.
I know I'll be flamed, but I think I'm going to put it back together. I ordered a LN spin on filter and mag drain plug. I have a filter cutter so I'll change the oil at 50 miles first and inspect the filter, then 500 and then 1000mi. Your thoughts........




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Anybody know why you’re not supposed to use compressed air to blow the dust out
On your dual mass flywheel and no solvents “brakeclean”?

Very interesting. Seems to be the perfect example of IMSB failure in a car that has not been driven enough. I inspected the IMSB on a 2000 Boxster with 115,000 miles on it, I pulled the outer seal and verified the bearing, it was fine. I put a new o-ring on the flange and put it back on, it has been running ever since without problems.
Was there any grease left in the bearing... or oil?
I find your course of action reasonable. With the bearing seals in place it seems to me that very little metal would be circulating.

No there was no grease whatsoever. Hey my tooling worked great..........

Are you saying you found the cage like this after removing the seal? Looks like a perfect cut.

Today I pulled the IMSB flange off the engine that I bought on ebay last Juin (and that just arrived after being stuck at the border) and the bearing is perfect. I removed the outer seal to check it out... turns smoothly and there is no play. Unless closer inspection reveals something I will put a new o-ring on the flange and button it up. The engine is supposed to have just under 99,000 miles on it.

Yes that's what I found when I pulled the seal for inspection. I certainly wasn't expecting
what I found. Anybody know what appears to be a patch/repair is in the photo?
Installed the new bearing, crankcase pan, RMS, flywheel and clutch today, tranny tomorrow.....can you help me understand why low mileage could have contributed to this failure? I don't get it, but glad I didn't like the feel of my clutch, that's why I went in to try and fix that and found what I found. Probably could have gone around the block a couple more times, you think.......





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Weird... My guess is somebody has already tried to pull the bearing out using a bearing puller and one of the arms of the puller broke the casting. This would explain the unusual failure of the bearing, it may have got damaged at the same time. Is it the original?

I don't get it either, but reading on this and other forums it is often said that IMSB problems happen more often in M96 engines that have not been driven a lot and not driven hard. Is there data to back this up? I don't know.

This is from the LN engineering site.

"Remember, not driving your car or worst yet, not driving it like Porsche intended can make the problem worse. Although a greatly debated subject, most experts agree that more frequent oil changes with a quality 5w40 motor oil like Driven DT40 every 6 months or 5,000 miles is a good first step. Secondly, actually driving your Porsche more often and avoiding higher gears to keep the revs above 2500-3000 rpm is another good step to take to improve the life of the ball-bearing in the intermediate shaft. Although there is limited data, the general trend is that lower mileage vehicles with infrequent oil changes or driven light-footed (as in run at low speed/engine rpms) are most likely to suffer a failure rather than those cars that are driven hard and well-maintained."

Like I said bought the car with 9000 miles, it had not been gone into
before this time. The repair history was oil changes and a belt. All done by Barrington
Porsche in Illinois. Yeah I’ve read all of Jakes stuff and I can assure you it’s driven
Like a Porsche and never “lugged” RPM is kept in the 3k area.

Changing oil does not require welding on the crankcase...

One possible explanation might be that the oil that gets trapped inside the IMS and hence in the bearing is overused and dirty as it`s not replaced with the oil changes. Also, the gas that seeps through the bearing during cooling-warm up cycles is crankcase gas, which contains CO2 and other potentially corrosive chemicals coming from burnt gas and oil. Now, if you leave your car unused for years, the bearing sits half way submerged in this dirty oil inside the tube. Being half way exposed to the oil for years may cause an uneven wear pattern which might lead to future failure?

This is just a theory that I just came up with, don`t take it for granted :)
But for this reason I added a "drain hole" to the IMS where the trapped oil can escape.

An additional note: my car had 100k miles and spent 11 years in a garage with the engine seized. The IMSB was original and in a perfect shape. But the oil it was sitting in was black and dirty.

A better and permanent fix would have been to install a plug behind the bearing, as is done in all IMS Solution retrofits. The IMS shaft tube is weak enough without drilling drain holes into it.

Actually I drilled the sprocket through while pinning it to the shaft:

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The idea is that centrifugal force is constantly pulling oil from the tube through this hole while receiving oil from the crankcase through the open end.

While we're on the subject of drilling and modifications; From my research, I believe the best, cheapest, and simplest way to keep fresh oil in the bearing is to tap a hole in the opposite end of the IMS shaft behind the oil pump and remove both seals from the IMSB. This way oil will actually circulate.

Full disclosure: I have not done any such mods to mine, nor have I changed the IMSB. But if I decided to do it, that's the route I'd go.

Yes, I'm aware of the DOF from LNE. While it's good, it's not the simplest nor cheapest. Plus, I'm a bit uneasy about having a pressurized external oil hose. My brother had an Audi with an external oil line. Unbeknownst to him, it ruptured and within seconds of the oil light coming on the engine was toast. The oil was pumped out that quickly.

I personally don`t like the idea of modifying the original oil lines, regardless of being external or internal, by adding a "leak" to the system. Especially by punching a hole right at the oil pump. In general, I don`t think it`s necessary.

I hear ya. The "leak", as you call it, would drip back into the sump. It's the same as all the other oil passages.

Everyone has their own comfort level, and you're certainly not wrong. :cheers:

I meant a leak causing a drop in the oil pressure. An engine oil circulation system is designed such that the oil pump is able to compensate for the oil loss at the bearing/bearing journal clearances. The pump`s capacity is calculated by the engineers such that it can keep up in all circumstances, high temperature, low rpm, low viscosity, partially worn bearings, etc. Here comes the user, and hits a hole with a mallet right into the heart of this delicate system. Most likely the loss is negligible and won`t cause oil starving, still, it sounds super sloppy and unprofessional to me. But it`s just my thinking, it`s totally fine if someone is ok with it :) :cheers:

Since everyone is mentioning their 'personal opinion' here is mine (please ignore if you wish..) :p

But having oil 'inside' the IMS shaft (IMHO) could cause imbalance issues, I first saw this 'technique' when I visited the shop that invented this technique Vertex (..?) and has not convinced at all..
.

Homeoboxster I’m aware oil changes at a dealership wouldn’t.........
My thought is this came right out of the factory with this.
A little history I’m 65 retired from CAT after 26 years as a field tech and 4
Years in the office. I am not a Porsche tech and don’t claim to be but I can
usually handle what comes up. I say this because I’ve seen some amazing things
Come out of factories, I’m not saying the repairs are scrupulous they’re just repairs
Professionally done. I should have said has anyone else ever seen this in
their motors or is this a one off?
Trannys back in, should finish this weekend with my filter adapter and mag
Drain plug arriving tomorrow. I’ll let you know

I also came across a few surprises while rebuilding my engine that had not been touched before me, but the crankcase welded like this? That is there for a reason for sure. Someone made a mistake at the assembly line and fixed it before anyone else would have noticed it? Just for your reference, this is how it looks on mine:

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Probably no one will shed light on what happened here and when... That bearing cage is another mystery to me.. :confused:

Anyways, I wish you no more surprises with the car :cheers:

I wonder about this as well. Does the hollow shaft fill with pressurized oil? If so you now have quite a mass of liquid rotating at relatively high rpm resulting in inertia and perhaps imbalance when the rpm’s decrease and increase. If it doesn’t fill but only partially then you have a liquid being sloshed around that has its own issues like cavitation. I just don’t think the shaft was designed to be an oil journal.

Generally thinking, it`s indeed not a very good idea to fill the IMS with about a quart of oil. But actually this happens every time soon after you turn off the engine if the seals are not perfect any more, or you have an open bearing, because the entire shaft is submerged in engine oil. As for the imbalance: this may have some significance at idle, when the IMS speed is around 4-500 rpm, but once you hit the accelerator pedal the liquid mass is quickly going to move to the periphery and will be perfectly balanced, and will be pressurized. The pressure will even force most of the oil mass out, through the bearing. Think about it as a centrifuge ;)

Sorry it’s been longer than intended......
Car seems to be running perfectly. On initial start up
I ran it to temp and shut down and cut open filter and it was clean
As well as my new magnetic drain plug. New oil and ran it for 50 miles and cut
Open filter, it had one very small piece that stuck to a magnet but just one.
Installed new filter and am going to drive it 500 miles and recheck it all including
Dropping the pan to take a look if all’s clean I’ll run new oil for 1000 miles.
I’ll let you know then. And by the way the clutch that started this all, does indeed
engage lower now and is smooth as can be on take offs. Yay couldn’t be happier!
Also ordered a quickjack 5000slx after all the jacking up I’ve done... gets here Saturday

Great work, Dave! Congrats!

Thank you, good or bad I’ll let you know.....but I will welcome all positive thoughts..... thanks