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IMS bearing .........again


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Hi Pedro from the UK,
I have a 2004 986 3.2 boxster 550 spyder. I have owned it for the last 12,000 miles/4 years. It's a 25,000 full dealer service history miles car, which I love. It has had an IMS bearing failure. I am a time served and experienced engineer with enough wealth of knowledge and experience to put this right. A factory short engine has been ordered and all other damaged parts (mainly related to cylinders 1-3, including the head and valve gear on this side) are being replaced. There will be no compromise of the build. My question is this, until the new short engine arrives, I cannot tell if the factory has built it using the externally replaceable ims bearing, which of course allows me to remove their fitment bearing and install the Pedro DOF kit, preferably the dual row bearing. Or, if it will be supplied with the later/larger ID & OD bearing (mid 2005 on), which would involve splitting the new crankcase to fit the DOF kit. Naturally, I don't really want to split a new engine case open. Yes, I'm aware that I can pop the outward facing seal from the already installed later bearing in the new motor and then fit the remainder of the DOF kit to my new engine. Here's the question, you have given highly informative video's over on this one and I respect your wealth of knowledge. However, IF the new bearing is not of the externally replaceable type, this would mean leaving the inner seal of the new factory bearing (the one facing the front of the engine (oil pump end) in place. In the videos reference is made to oil which finds its way past the inner seal and sits in the hollow sealed cavity of the bore of the ims shaft, only to get cooked and by way of expansion of air in the "tube", get forced back through the ims bearing. Is this going to be a problem since with your kit there will otherwise be a good supply of healthy oil (better by far than using the original lubrication design, namely none)? All the same, does the cooked oil from within the ims shaft compromise the bearing? One final question, the oil supply that your kit uses taps off from the camshaft bearing cap supply? If so, does the "bleed out" of oil used to fire at the inner race/balls of the ims bearing compromise the oil pressure to the cam bearing caps please? I apologise if I appear to be anal about this but need to be sure since I really don't want to do it all over again sometime.
Thank you
Mel.
Hi Mel:
If the engine was rebuilt by Porsche then it will have the larger single row bearing from the 987.
The solution is to pop the outer seal out and install the DOF2 Kit.
If any oil were to make it past the rear seal and into the IMS and became rancid and acidic an then made it back into the bearing it cannot do any damage because it would be immediately washed away by the stream of oil.
The stream of oil is picked up at one of the heads but the valley that feeds it is exclusive to the port and does not rob oil from any other component and the oil pressure regulator keeps the pressure exactly where it needs to be.
Even though the 2004 550 has the highest IMS failure rate of any other Porsche there has never been an IMS bearing failure after the DOF has been installed.
To my knowledge we have sold several hundred DOF2 Kits for 2004 SE 550s.
Happy Boxstering
Pedro

Pedro Bonilla 1998 Boxster 986 - 280,000+ miles: http://www.PedrosGarage.com
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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