insite

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.

Flat6 Innovations

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.

inviktus

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!

insite

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.

Cefalu

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.

Flat6 Innovations

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.

Cefalu

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.

perryinva

Any special tools needed for the clutch replacement?

Cefalu

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.

Flat6 Innovations

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 :-)

Cefalu

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.

Flat6 Innovations

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.

insite

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......

Charles Navarro

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.

Cefalu

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.