IMS center bolt

[WhiteyII]

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.......

[Homeoboxter]

Originally Posted by WhiteyII

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?

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?

[elgyqc]

Originally Posted by WhiteyII

.....can you help me understand why low mileage could have contributed to this failure? I don't get it....

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."

[WhiteyII]

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.

[Homeoboxter]

Originally Posted by WhiteyII

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...

[Homeoboxter]

Originally Posted by elgyqc

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.

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.

[JFP in PA]

Originally Posted by Homeoboxter

But for this reason I added a "drain hole" to the IMS where the trapped oil can escape.

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.

[Homeoboxter]

Originally Posted by JFP in PA

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:



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.

[piper6909]

Originally Posted by Homeoboxter

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.

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.

[Homeoboxter]

Originally Posted by piper6909

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 and 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.

[piper6909]

Originally Posted by Homeoboxter

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.

[Homeoboxter]

Originally Posted by piper6909

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.

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

[Gilles]

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

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..
.

[WhiteyII]

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

[Homeoboxter]

Originally Posted by WhiteyII

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:



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

Anyways, I wish you no more surprises with the car

[paulofto]

Originally Posted by Gilles

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

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..
.

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.

[Homeoboxter]

Originally Posted by paulofto

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

[WhiteyII]

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

[piper6909]

Great work, Dave! Congrats!

[WhiteyII]

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