Not another IMS thread!

Yup, it is. I pulled the tranny yesterday. I ordered the clutch kit yesterday and the IMS bearing from Raby this morning. All in all not too bad of a job except for the upper trans/engine bolts and clutch slave as noted by everyone so far. But it does help to remove the front trans support early on and tilt the trans down to get better access to the slave and those two bastard bellhousing bolts. That upper bolt was a real bear until I realized I can get it with 3' of extensions from the back of the trans. The good news is nothing was leaking after 60k miles. Just a weeping that had a bunch of clutch dust absorbed onto it. But some clean oil did come out of the bellhousing bolt that goes right below the oil cooler on the pass side. Maybe 4 drops. Question; how do you know if the flywheel is good or not? They are $700 and I don't want to replace it if I don't need to. But I don't want to cheap out and go through this again if I don't have to. Right now it has resistance but I can rotate it back and forth with my hands.

At the shop, they said if the two halves of the flywheel still move -- it's ok -- but can be replaced if the car has a lot of miles, etc. I think you can rotate the halves and the springs should snap them back into position. If the two halves are solid and only rotate as a single mass, or the springs won't snap the halves back into position -- the flywheel should be replaced. I know others will chime in -- probably with better/more precise info.

Thanks for the order.. We'll help you through the IMSR process. Post some pics of the flywheel and we'll see if they look like the wear surface is questionable.. Thats one of the elements to determining if it's ok to reuse or not. This is the busy season (we HATE it) so it might take a day or two for the bearing to ship.. My Parts Manager will be in touch soon.

+1 for James on flywheel what did you clean with, looks minty fresh! nice and dry to start too

OK, here are the pics of the flywheel. The flywheel returns back to center when you rotate either direction, and it does have a fair amount of resistance to rotating from center position. I cleaned the area with a water based detergent called oil eater. I sprayed the oil eater on and used a brass brush to scrub the dirt away. Then I rinsed it all off with a can of carb cleaner. Even though my RMS was not leaking, would I be well advised to change the RMS anyway? I don't know if this is one of those cases of letting sleeping dogs lie or not. From what I have read, off center machining of the case at the RMS is the cause of the leaks. You can't get the seal to work correctly because the crank is not centered in the rear main seal. But I thought mine looked as good as any car I have seen. But if it's a simple and reasonably risk free R&R, then maybe I might be inclined to change it.

In hindsight the trans removal was actually pretty easy. What surprised me was the goofy wrench and socket sizes. Most of my wrenching has been done on Alfa's, BMW's and Mercedes. Those typicall use 10, 13, 17 and 19mm sockets/wrenches for practically everything. The Porsche used 10mm on the belly pan, 13mm on the clutch slave (2), 15mm on the trans supports (6) and 16mm on the bell housing bolts (8). Plus one weird 12 spline 12 mm socket on the bellhousing and a T55 on the flywheel bolts. Oh, you also need an 8mm Allen head on the CV joints and 6mm Allen on the clutch cover. And I had to use all the u-joints I had and some wobble extensions. I don't think I have ever used a 15 or 16mm on anything. And 90% of this job was done with those two sockets.

excellent time to do the 2nd gear detent upgrade http://www.gboxweb.com/detent.html

Just when I thought I knew all the weaknesses of these cars....I discover that 2nd gear pops out. Looks like a reasonably easy fix though.

A Porsche tech tells me the flywheel check involves seeing how far one can rotate the flyweel against the dual mass thingie. I forget though how many degrees of rotation is acceptable and how many is not. Sincerely, Macster.

from TSB 911 (996) 8/02 1360 Dual Mass Flywheel Check procedure http://www.renntech.org/forums/index...-procedurepdf/ Can the dual Mass Flywheel be twisted approx. 15mm in each direction, left/right, and does it return to approximately its initial position? If so it is good. Can the DMF be twisted beyond dim stated above without a noticeable increase in the spring force? Or is it fixed (no rotation?) if so bad

RMS data point FYI When I pulled my trans my RMS was dry I replaced it with the latest upgrade. I got to do that 2 more times until it was dry again. The new encapsulated bolts and IMS seal were fine after the first time.

Thanks Frank, I was a afraid of that. It seems that the RMS seals have the most trouble in cases with alignment issues. And since mine seems to be OK, I might just let it stay put, until my next clutch job.

Oh Boy, The UPS man visited today. And I got two presents.

goodies!!

Wow! Shiny things. DON"T GET THEM DIRTY!!

Hey Jake, (and anyone else who professes to know the answers) The flat 6 / lNE bearing kit has arrived and although I have read every IMS thread on the internet, (and the 1 page LNE instructions) I still have a couple of questions. FWIW, the Porsche in question is a 1999 C2 6 speed cabriolet. 1. There are 3 chain tensioners to remove. Two are reasonably easy to access and the third is a bear. Most people are saying you only need to remove the 2 easy ones and the third is "optional" True? 2. The engine needs to be locked at TDC. Finding TDC is not easy. But locking the engine at either TDC or 360 degrees off TDC is easy. I read somewhere that either TDC or 360 off TDC is acceptable, both positions have the cams unloaded. 3. I read in one post just about a year ago that you were developing an installation DVD and the DVD was pretty close to completion. You commented that a DVD would ship with future kits. I did not get a DVD in my box. Does one exist? 4. Someone suggested that it might be easier to replace the slave cylinder bolts with studs and nuts. I can't recall how the slave fits on. I am all for changing bolts to studs and nuts if you think it's an option. I will be feeling a whole lot better about this job if I can just stick the crank lock pin in at TDC or 360 off and pull the two tensioners and GO TO TOWN! I'm ready to get this poor car back on the road. It's been lounging in my garage for too long. Thanks, Doug

I was wondering if the locking pin in and the pulley tick mark lines up with the mark on the engine - is that TDC or can that be BDC also? PS. good question if you need to back out the 3rd tensioner-

First off.. Forget TDC/ BDC per cylinder. Lock the crank at TDC as instructed and don't worry about "why". People over thinking this is the source of issues, because the design of the M96 doesn't matter what cylinder is at TDC or TDC overlap. Sure.. Since you got our bearing, feel fre to call me directly for support. I won't answer the questions of those who don't buy from us, but you did pay for support. Ok, all are created equally, from a 1997 2.5 through a 2008 3.8 By the book you are supposed to pull all 3, practical application tells us that you don't have to. The choice is yours. IT DOES NOT MATTER!!! TDC on cylinder #1 is TDC overlap on cylinder #4. TDC #4 is TDC overlap on cylinder #1. THE PROCESS CAN EQUALLY BE CARRIED OUT IN EITHER POSITION. Lock the crank at the position of TDC and don't worry about if thats #1 or #4. Lock the crank and forget it. Its on my hard drive.. Its partially edited, but is far from being finished. We have revised the procedure 3 times in the past year and have made more tools to lock cams and etc. We can now finish it, but it won't be anytime near term Thats up to you, I am an "internalist" Do it.

Thanks Jake. Fair enough on the support issue. There ia a local independent shop that agreed to loan me a rear main seal driver tool and a clutch alignment tool over the weekend. So the RMS is getting replaced as well. The shop wants to check out the new ceramic IMS bearing, so he asked me to bring it in when I borrow the tools. He was not familiar with the LNE design, but he said they have been doing replacements with the factory stock bearing. Which surprised me since I didn't think Porsche was selling them separately. I might be pulling the bearing Friday. If I can't get to it, can I call on the weekend if I run into trouble? And what is the number I call?

nice job...

OK its showtime! IMS flange pulled, not a drop of oil, tight bearing and rubber for race fully intact. Bearing puller goes on next

Bearing is out! Very simple. takes some force to get the bearing to pop out of the circlip but not bad. Then pop! and its easy from there. Lots of oil poured out from behind. But clean and not burnt smelling. Bearing is tight in its race. zero play. Both sides have perfect seals. This bearing was definitely not a problem at the moment. Tensioners looked good too. No scoring, clean and free. I pulled 2 of the 3. I did not pull the 4-6, and don't think it's necessary EVER. That tensioner is connected to the chain that wraps around the belt pully sprocket (opposite side) If the belt pully is pinned, there is no way you could get movement over there. Now to pull my new bearing and driver from the freezer and install.

That's good to hear.

All done toughest part of the bearing job was the circlip for the double row bearing. you need 3 hands to put it in. Actually the toughest part was replacing the AOS. That's a PITA. Big tip: put the clutch slave on before you connect up the tranny. You have lots of access to the bolts. Takes 2 mins.

Excellent! And you didn't even have to use the support that came with the bearing!

I just had my tranny out and replaced the AOS, clutch, PP and bearing. RMS was perfectly dry so I left it alone. By your description your flywheel sounds like it is fine. I would recommend taking a 3M pad and scuffing the mating surface of the flywheel, cleans up the burnished area where the clutch disk has been riding. This will help bed your new disk. As a side note, I didn't do the IMS as I have a replacement engine from Porsche with the revised single row bearing. Replaced by Porsche in 2006.

I finished last night at 11. But I forgot to buy oil so I couldn't fire it up! The moment of truth still awaits. It's a long job but not technical, aside from maybe the bearing R&R. Here are a few tips for those who may want to get intimate with their car 1. R&R the clutch slave when the trans is down. The slave is attached to a flex line so you can drop the trans down for easy access to the bolts. People have talked about spending hours on the slave R&R I spent just a few minutes. 2. You do not need to pull the tensioner for cylinders 4-6. That chain is attached to the opposite end of the crank from the IMS bearing. When you lock the drive pully with a dowel that chain isn't going anywhere. When you pull the tensioner for cylinders 1-3 be prepared for all your oil to drain out if you didn't drain it already. I had just done an oil change and didn't want to drain it, but once I pulled that tensioner, all gone! Incidentally, the independant shop I borrowed the main seal tool from said they don't bother to pull any tensioners at all! Pulling those 2 tensioners is fast and easy insurance. 3. To access the upper bell housing bolts you need about 3 feet of extensions and a good universal. Go with 1/2" drive. 3/8" flexes too much. 4. The axle half shafts are 8mm allen. Break the half shafts loose with a short allen, they are tight. Get a long, say 5" allen to R&R while they are not torqued down, it will go faster. The long allen helps get around the rubber bellows. Use the short allen to torque down. 5. While you are working on the car support the engine bottom with a floor jack. It will make your life way easier to get at all the misc bolts, and facilitate aligning the engine to trans when you are mating it up. I was constantly moving the engine up and down when doing the AOS, RMS and IMS bearing. I also replaced the 4 bolts that connect the case halves. But! the floor jack will not support the engine long term. You need to stick a support under it when you are not working on the car because th ejack will leak down. 6. The AOS is a bitch to get to even with the trans out. It was definitely the hardest part of the job. The two ~1" Dia. hoses are a bear to remove. They do have reusable connectors. But the small coolant lines (yes coolant) lines to the AOS have crimped clamps that I cut off with a big pair of really big pair of wire cutters. Lousy access. I thought the small lines were vapor lines so I got a coolant surprise in the face. The two bigger hoses use O rings. Order them and replace them. I think they are 18X2.5MM. Naturally, my dealer did not have them in stock. 7. The RMS is pretty straightforward. I used the latest one for the Cayenne. I drilled two holes on opposite sides and used screws and hammer claws to pull it out. You need decent sized screws. The small ones I used at first pulled out. 8. The IMS is pretty well documented already. Lock the crank pully, pull the two tensioners, (main and 1-3), pull the flange cover off, screw the hex adapter all the way down on the IMS threaded shaft then thread on the removal tool. The torque needed to remove was not too bad, but felt slightly uncomfortable. So I let the tool sit for 5 seconds, and turned the nut again and it popped and it was home free from there. Put the bearing and driver in the freezer first to shrink. Mine went right in without too much beating. It was a snug fit but not too much so. all in all not too bad

interesting that the indy shop said they dont pull the tensioners- an indy over here told me they dont need to change the oil ( im assuming they dont pull the tensioners either )

Not pulling the tensioners for an IMSR?? Someone is on crack. Take that from the guy that did the first one LN Retrofit! ALL tensioners are dirty, they need to be cleaned if nothing else. Someone did this without changing the oil? Thats horrible! the new bearing will love all that dirty oil while it is going through its initial break in process.

I agree, new oil if anything PS. why do you need to pull the tensioners ( remember there are no stupid questions--- )

haha you absolutely have to remove the tensioners. if you don't, the INSTANT you remove the IMS flange, the entire shaft will pull way over to the right INSIDE the motor. tough to correct.

The tensioners tension the timing chains. The timing chains are linked to the IMS. Not removing the tensioners leaves tension on the IMS. If the IMS is tensioned when the flange is removed it is very easy for the engine's cam timing to be compromised. Not pulling the tensioners is just pure laziness and is more than likely being executed by someone that is making "book time" doing the procedure, working from commission.. To these people working as fast as possible is good for their wallet, but can be very bad for yours. Here we don't have a clock, nothing is done by the hour and it takes as long as it takes... I hate lazy people that don't do their job completely and thoroughly and treat the car like it was their own.

Cefalu: great thread and thanks for posting. I have a question for you (and for Jake, and for anyone else who has done this job): my mechanical experience so far is limited to suspension, brakes, and engine bolt-ons. I've never cracked into any part of the drivetrain beyond fluid changes. In your opinion, is this sufficient background to do this job on jackstands? Does your answer change if the car is on a mid-rise lift instead? I really want to do this myself, but I also don't want a) the car to be up on a rack for 12 weeks, or 2) to get stuck on a bell-housing bolt with the car in pieces around me. Don't worry, I'm not going to hold anyone responsible if I choose to dive in and it goes bad. Just polling for opinions from those in the know. Thanks!

the job really isn't that tough. if you have some mechanical aptitude & experience, you can definitely do this in your garage on jack stands. just get the car good & high & make sure your method of lifting & lowering the transmission goes high enough to reach. just take your time & follow the instructions. you will be a better man for having done it! going SLOW, you can easily knock this out w/ a few hours a day over two weekends. use the opportunity to look around for other issues you can prevent / eliminate / plan for.

OK, success! replaced the oil and filter and fired it up. Perfect running, but it never had an issue aside from a slipping clutch. I cut open the old oil filter and it was perfectly clean. The car runs great. The old clutch was a little grabby and stiff. The new clutch uses a lot less pedal pressure but engages lower on the pedal. I have read here that a stiff clutch pedal is a sign of a worn clutch and I can confirm that observation. Although it is relative so you will need to feel it both ways. I did this job on 4 jack stands I bought from harbor freight. I also used two harbor freight floor jacks. A high lift super heavy floor jack to get the car high enough for the jack stands, and a lightweight aluminum one that fits in low clearance places. I really like the aluminum jack, it's perfect for oil changes. I also bought a cheap harbor freight transmission jack. I have never had one of these harbor freight floor jacks fail, but they are made in China so I would never place myself in a situation where if it did fail I would get hurt. I always assume the seal will blow out. The jack stands are each 5 ton rated and I used 4 of them, one under each jacking point. The car never felt unstable at all, really very solid. My car was on stands for nearly 3 months while I pieced together enough time. I am not a mechanic, nor have I ever worked as a mechanic. But I would say I am mechanically inclined and have done my fair share of wrenching. Mostly on Alfa's. The Porsche is easier in my opinion. This is not a hard job. The tips to making this job easy are to get at the bell housing bolts with 1/2" drive tools with a universal socket. The top bolt is easy to get to once you remove the trans support and tip the trans down. And R&R the slave while the trans is down; the bolt access is no problem then. If you were a beast and pulled two 10 hour days you could knock it out in a weekend. It took me three each two hour days, and one 10 hour day. But I did the RMS, IMS bearing, clutch and AOS. The clutch takes no time because you take it apart anyway. But this is definitely one of those "while you are in there" type of jobs. I did need to replace my clutch and even though I was not experiencing IMS problems I replaced it, and even though my RMS was not leaking, I replaced it, and even though my AOS was not exhibiting any signs of failure I replaced it. I cannot imagine trying to replace the AOS from above, what a nightmare. Someone suggested replacing the clutch throwout bearing arm, but my Porsche dealer did not stock the parts, so I did not change it. Regarding the Chain tensioners, the two that you need to pull are very easy to access and remove. There is no excuse to leave them in place unless you were an idiot or you did not know better. The 3rd tensioner (cyls 4-6) is attached to the opposite side of the intermediate shaft. It cannot exert any loads on the bearing, so there is no point in removing it. Which brings up another point. The opposite end (crank pulley side) of the intermediate shaft is also fixed in a bearing. The intermediate shaft is restrained to a certain degree from moving around from the bearing located at the crank pulley side. So I can see how some indies get away without pulling the tensioners. But considering the downside risk to losing cam timing and how easy the tensioners are to pull, there is absolutely no excuse to not pulling those two tensioners. Maybe it adds 5 minutes to the whole job. THAT SAID, I have a 5 chain motor, not the later 3 chain style. My intake and exhaust cams are locked together with separate chains the 3 chain motors dont have.

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The process is ALL ABOUT following procedure. The system in which the processes are carried out means everything to the level of success that you'll have, as well as fun during the process. Some people want to do things their own way, or create shortcuts. These people try to pull the engine apart before the tool kit arrives "to save time" then they realize that they took the engine apart at the wrong crankshaft position. At this point the job just became 500% more difficult. Those who take their time, follow procedure and exercise common sense end up with results like Cefalu, who did the procedure and never even had to use his support that came with the bearing kit. The success is up to the person doing the procedure. The procedure is proven, at least 50 retrofits are being carried out all over the world every week these days.

Jake, one last question about the cyl 4-6 tensioner. On my Alfa's, the DOHC cam design meant that if you took the timing chain off a cam sprocket, the cam would likely twist out of time due to valve spring spring pressure rotating a cam lobe. But the 996 engine uses hydraulic lifters. Wouldn't the lifter bleed down and release the pressure so the valve spring is not so loaded against the cam lobe? if it does, I would think the risk of the cyls 4-6 cams rotating out of time would be minimal, if at all. Unless of course the lifters bleed down too slowly to release sufficient spring pressure.

Any special tools needed for the clutch replacement?

It depends whether or not the clutch job includes the AOS, IMS RMS or not. A straight clutch job just needs the usual metric assortment of wrenches and 1/4", 3/8" and 1/2" drive sockets. It's not special, but a 6mm Allen for the clutch cover, an 8mm allen for the axles, a T55 Torx on the flywheel bolts (if you remove the flywheel) and a 10mm triple square male socket for one lonely bolt on the bellhousing. Although I read where someone used an allen wrench to remove it. The bellhousing bolts are easily removed with about 3' of 1/2" drive socket extensions and a universal. A torque wrench. And a clutch plate alignment tool. You need to rotate the flywheel bolts 90 to 120 degrees after you reach 19ft lbs of torque. I set each bolt to 19 lbs then I marked each bolt with a sharpie so I knew where to stop rotating. Sharpie.

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This is where experience from other engines isn't beneficial.. If you attend my engine rebuild school you'll learn that at TDC EVERY VALVE in the M96 is "off lobe". The engine was designed in this manner and all camshafts are relaxed at this point. You are "overthinking" the situation, thats why we tell folks to just follow the instructions and don't worry about "why" something is done :-)

Since that's the case, LNE should remove from their directions that you need to remove the cyl 4-6 tensioner. That tensioner alone doubles the IMSR labor. Sometimes CYA serves no beneficial purpose to anyone.

But the problem with that occurs when the owner of a shop that wants to be critical busts our ***** for stating that this can be done with that tensioner in place.. Been there. Its a never ending search for the happy medium of proper instruction without being blamed for cutting corners. The removal of the 3rd tensioner to me is up to the judgment of the person carrying out the procedure. You should see what we have to deal with.

i do know one person who tried this job with the 3rd tensioner in place; he couldn't get the IMS lined up enough to get the flange back on. once he removed the tensioner, all was well. i also know several people who left it in place......

That's why we list it as optional. In the Porsche manual, it shows only two of three being removed. I know at the Porsche dealership locally, they pull all three when doing the IMS Retrofit procedure. You have those rare cases where the timing might have shifted from - 0 - and because of this, the shaft can be loaded in a way as to make removal or re-installation of the bearing and flange difficult or impossible. There are also many shops who don't lock the cams, just pulling the tensioners out at TDC and moving along. Straight from a Porsche tech I was told that you can get away with doing that, but in a small percentage of jobs, the cam timing will jump, requiring you to reset the cam timing. When doing things on the clock and you get paid an certain number of labor hours regardless of how long it takes to do the job, some are willing to cut corners to save some time (and make more money) and take that risk. This is probably one of the most frequent things I get calls about.

OK, I get that. If the cam timing was off before you started, then you may have the cams loaded up which could force the IMS shaft out of position. In cases where you were able to do so, taking a cam timing reading before you started would be a deciding factor as to whether or not the 3rd tensioner should be removed. I see that the LNE instructions do say to take a cam reading first (and when completed), which I did not do because I did not know why or what to do with the data. And my trans was already out. I lucked out because my cam timing was good before I started, probably in part because my bearing had not yet failed. But the LNE instructions I have do say to pull all 3 tensioners. Thanks to you and Jake for developing the ceramic bearing. Now I won't be worrying about that bearing disintegrating every time I hear a new sound from the car. There is no better sports car value out there than a 996 or Boxster with a retrofitted IMS! I can't believe the bang for the buck with my car.

The instructions have to default to the "most complete" way to carry out the procedure. If not there are people standing by to crucify us for not stating "the proper" way to do the job. Lots of geniuses out there that really don't have a clue.. And they are the most opinionated asses on the planet. We have to deal with them all the time.