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Liquid Cooled M96 IMS engine retrofit


m96-1Bodymotion has become the “go to place” for liquid cooled 911 engines. Our building of race engines from Boxster/Cayman,996/997 to GT3 Cup engines has given us considerable experience with the term “been there, seen that” Our telephone, web site and e-mail are busy assisting customers from all over the USA and foreign countries. Questions range from those regarding basic stock street Porsches to Club and full pro race cars. They span the gamut from Porsche cars in-warranty through high mileage daily driven street cars. One of the common ailments frequently discussed is the leaking RMS or rear main seal. These leaks have caused quite the stir, especially when performing pre-purchase inspections. We have heard “I have replaced that seal more than once!” from frustrated customers time and time again. The newer replacement seals and the very expensive installation tools help to assure that a repeat failure is not in their future. However, and getting more common, is another often miss-diagnosed engine oil leak, from the same flywheel clutch area. Because of all of the RMS hoopla, the assumption is that the RMS is causing the leak, when in fact, the culprit, may be the new Achilles heel of the liquid cooled engine, the INTERMEDIATE SHAFT BEARING AND SEAL .

m96-2This troubled area is a highly stressed, critical area of the engines reciprocating mass. As such, we are seeing an alarming rate of failure of this bearing and seal. It is necessary to remove the gearbox and clutch to view both the rear main seal and the intermediate shaft flange. Because the intermediate shaft flange is directly below the crank seal, it is often over looked. The seals usually leak when the highly stressed bearing at the end of the shaft begins to fail (flywheel end of the engine). When this bearing begins to fail, oil leaks out of the area. Metal particles from the bearing begin to mix with the engine oil. Noise can be heard, with the engine running, at this end of the engine. If recognized, and repaired before it breaks, you can save the engine. “SAVING THE ENGINE” What on earth does this mean? Quite literally, once this part fails totally, the camshaft chains can no longer keep the precise timing with the crankshaft. This type of failure is tantamount to breaking a timing belt on a 944. Boom! No warning. As the driver watches the engine oil that rapidly pours out onto the pavement, he may scratch his head and wonder what’s next. An appropriate analogy would be similar to the draining of ones wallet after it is towed to the shop. After it fails there is no economical
repair, all of the valves bend, and all of the timing chains get ruined as do most of the timing gears and actuators. It is quite literately cheaper to buy a replacement engine. Replacement engine costs vary, according to model year, displacement, transmission type etc. But, trust me; avoidance is the best route here.

m96-3The best advice is to have the IMS bearing replaced if any metal is found in the engine oil, also if you hear a grinding or whirring sound that has gradually gotten more noticeable. Also, increase your oil change intervals, Synthetic oil 7500 miles for street, 5,000 for occasional track or autocross. Track cars for DE, every other event, Full race cars, every single race. Boxsters, Caymans and 996’s with 3.4 or smaller displacement, we recommend replacement during routine clutch replacement as most of the labor is overlapping. Later 997’s, 2007 and on, have a wider bearing and shaft and are less prone to failure. If you want more technical information on the history of the intermediate shaft troubles, engineering data, and replacement solutions, please visit this web site.

We have performed the IMS upgrade as outlined in this article with excellent results. We believe we have extended the engine life and many Porsche club members’ cars. We have a complete engine here on display that has failed. We also have parts for you to view that we have removed from blown engines.After many updates and revisions, Porsche finally decided to give up on the Intermediate shaft (used in one form or other since 1965). The solution was to direct drive the cams from the crankshaft, just like the GT3 and twin turbo engines. All 2009 and later direct fuel injected Porsche models with boxer style flat six cylinder engines no longer use an intermediate shaft.

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