| Saving an engine, IMS retrofit |
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Saving an Engine! Removal and replacement of the problematic "dual row" IMS bearing! (a task once believed impossible is now a reality) Story and Photos by Jake Raby
NOTE: The below procedure illustrates one of our three methods of IMS bearing extraction, perfected as of 12/1/09. All IMS bearing kits now sold by Flat 6 Innovations have a proprietary one time use tool available for bearing extraction that is not depicted in the procedure below. This puller is the simplest and most effective method we have found to date to remove an IMS bearing from the M96 engine and it is also the most cost effective. Please bear with us while we complete a comprehensive DVD on the topic of IMS bearing extraction and insertion to be released in late 2012. The below procedure can be used as a reference, but the puller has changed.
For the majority of three years, Charles from LN Engineering and I attempted to come up with a solution for the dual row IMS bearing and had dismissed the possiblity of making a retrofit after several failed attempts at bearing extraction. What prohibited us from applying an "overkill engineered" solution, including ceramic hybrid bearings like those used in LN Engineering's IMS Upgrade or single-row bearing IMS Retrofit kit, was our inability to safely remove a dual row bearing with the intermediate shaft still installed in the engine. The bearing was pressed in and retained with an internal wire lock and every puller that was used to pull the bearing ended up broken in the process, so we had honestly given up on being able to create a preventive or repair for the dual row bearing and then the aforementioned puller came into play and we capitalized on it.
I'll go over the processes of the bearing removal and replacement below and then I'll give a summary of some risks at the end of the pictorial. We'll start with the M96 engine in our customer's Boxster (that agreed to be one of our beta testers) opened up and ready for the IMS retrofit. To keep the article to the point we have begun with the transaxle removed, chain tensioners extracted, flywheel removed and the IMS bearing retainer also removed, exposing the dual row IMS bearing. Using a soft faced mallet, the center stud (bearing support) of the IMS bearing is tapped into the IMS tube to allow for the puller to be inserted. The intermediate shaft is comprised of a hollow tube which is captive, so there is no fear that the stud will fall into the engine's crankcase at any point. The center stud is removed after the IMS bearing is pulled using a magnet. As the center stud is not used in the LN retrofit kit, it does not need to be retained.
Here the center stud has been dislodged and is now held in the IMS tube awaiting retrieval. In this picture, the dual-row bearing is exposed, and does not feature an external circlip as found on single-row bearing intermediate shafts. Note that the IMS bearing is a sealed bearing, compared to the open bearing later featured in this installation.
Here we have inserted the first special tool made by LN Engineering. This bushing helps to support the bearing puller better and removes point loading from the feet of the bearing puller onto the crankcase. Left unsupported, this point loading **could** break the crankcase due to the extreme pressure being applied in a small footprint, especially knowing the casting alloys used to make the crankcase are not the strongest. The LN Engineering tool puts the pressure directly on the end of the intermediate shaft housing which the bearing is retained, eliminating any loading of the case, chains, sprokets, or any other internal parts except the bearing itself. Note the serrations (grooves) machined in the tool- these interlock with the feet of the bearing puller to eliminate slippage of the bearing puller under load.
Here the bearing puller is being initially tightened. Care must be taken to expand the collet as far as it will go as to pre-load it against the i.d. and rear of the inner bearing race, as if it slips, the collet will be damaged and will not successfully extract the bearing. Note how well the feet of the puller engage with the machined grooves in the special tool. We have also modified the bearing puller to have a hex to allow use of a box wrench rather than the wimpy T handle supplied with the puller. Now the bearing is under load, awaiting the bearing to be dislodged. This requires extreme force, more than any of us ever felt comfortable applying directly to the case, hence the importance of the serrated tool provided by LN Engineering! Here the bearing has just been dislodged and is being pulled fairly easily now. What allows the bearing to come out easily now is that the internal wire lock has been deformed, forcing it to compress into the outer race's loc groove, releasing the bearing from the housing. Here the bearing is about 1/2 way out of the IMS tube. Now the bearing is 3/4 the way out of the tube and the puller is removing the bearing like butter. Almost there! Here the bearing has contacted the feet of the puller and is fully removed from the tube and is contained within the tool used to support the bearing puller, also containing the wire lock from falling into the engine during extraction. Extraction of the dual row IMS bearing is now complete! Several knowledgeable Porsche-trained and employed techs said this could not be done, but these pictures don't lie! Here the bearing is attached to the puller and the tool and bearing are removed from the IMS completely! Mission accomplished! Look inside the IMS tube at the nasty oil. Even though the original bearing is sealed, oil does slowly get in, washing out the permanent lube, and fills the IMS with contaminated oil, especially on cars serviced with extended drain intervals. It is our hope that this procedure and these tools can save your engine from complete catastrophe! Now we'll fetch the center stud from the IMS tube and begin cleaning and prepping the area for the LN Engineering dual row bearing IMS Retrofit kit.
Sorry, but no detailed, up close pictures of the dual-row hybrid bearing are available, but photos of the ceramic hybrid bearings used are available on LN Engineering's website.
Here is the best shot of the new bearing. Note that we have removed the outer seal (we leave the inner seal on to limit the amount of oil getting into the IMS while allowing ample lubrication of the bearing, which is how it should have been from the factory). Using a sealed bearing in this environment seems to be a one of the contributing factors to the abundance of IMS failures. The washers pictured will be removed, they were improvised to hold the center stud in place during bearing install. LN Engineering's installation tool actually is countersunk to allow you to hold the center stud in place and drive in the bearing at the same time with a single tool.
...now we'll lubricate the IMS bearing flange seal and install it. Note that this prototype IMS Retrofit kit uses a factory flange which has been modified to work with the billet chromoly center bearing support stud.
Now we'll install the flange retaining bolts.
....and then we'll tighten the center stud and call this a complete job. Now that the installation is complete we will update the RMS, check torque on the fasteners in the bellhouse and then reinstall the flywheel, as well as the transaxle. Typically we invision the installation of a Retrofit kit at the same time as a clutch job, as the majority of the labor is shared between both tasks. This is a task that isn't completed at the present without a degree of risk as there are several things that could occur should the bearing be too difficult, or impossible to remove: 1. When pulling the bearing, the tool can break. 2. In instances where a bearing has failed or is in the process of failing, the bearing could break and the removal process may not be successful, making for a more difficult procedure with risks of introducing foreign object debris into the engine that could cause another component to fail or even facilitate a complete teardown to properly fix the IMS. We honestly believe that in this scenario, had the engine been left alone and continued to have been run, a catastrophic failure would have occurred, requiring a complete teardown, so if the bearing extraction had failed, you wouldn't really be any worse off than you already were! We offer this service as a "preventive" measure for those who want to be part of our R&D program. If you are anywhere in the USA and need a clutch or serious service for your Boxster or 996, contact us about the possiblity of having your engine updated with LN Engineering's Retrofit kit. If your M96 engine has a failed or failing IMS its worth all the risks involved to apply this development. Since the engine is already broken the "risks" are not of much concern as it would have to come apart anyway to repair the bad IMS bearing. Contact us directly with any questions/comments at This e-mail address is being protected from spambots. You need JavaScript enabled to view it Shipping of customer vehicles to our facility is a routine occurrence as we have very few local clients due to our remote location. Click here for details on our IMS Service Jake Raby |