which ims bearing upgrade

[Jamesp]

Originally Posted by 911monty

James I would argue that Pedro may not be completely correct. While the thermal dynamics of heating and cooling are certainly correct I suspect there is a problem with the gas law. During the cooling cycle there are 2 phases in contact with the bearing, a gas phase and an oil phase. Since fluid flow is always to the path of least resistance then the gas phase must preferentially move through the bearing during heating and cooling cycles before the viscous oil. I suspect this eventually pushes out the grease and causes the seals to fail, then the oil simply equalizes through the bearing by gravity. A sealed bearing could very well be fine if there was a vent hole in the IMS shaft. Just my thoughts.

The seals are never "perfect", they always leak. The Pelican refit kit sent me a non contact bearing that clearly would have allowed gravity to pull oil into the the IMS easily and certainly a worn seal could do the same, so this is a good point. A driving factor even with a good seal on a sealed bearing would be the delta p after running. I vented my IMS shaft on rebuild for precisely the points you make above.