Quote:
Originally Posted by JFP in PA
A couple of responses:
3) The seal facing the flywheel tends to harden and shrink over time, allowing oil to enter the bearing and wash out the grease. We have seen many bearings, dual and single rows, where the grease was gone, but relatively little oil was in the shaft. We have also seen both with totally flooded shafts, which may be a function of heating and cooling pulling the oil in, but as several of the non-flooded shaft bearings showed considerable degradation, it is the grease getting washed out and poor lubrication that leads to bearing failures.
5) The oil level only normally reaches the bearing level when the engine is not running; people fail to realize how far down the sump level drops with the engine running, particularly if it is running hard. Porsche put oil scavenging pumps in the cylinder heads for a reason: To get the excess oil trapped in the heads back down to the sump to keep the sump oil pump pickup covered. We actually tested this idea many years ago during an engine dyno test by drilling the case on a track car engine and installing barbed fittings with a clear hose in between them so we could see the oil level at various RPM levels. The oil level drops almost immediately after the engine starts and drops way more when the RPM levels go up. Even under modest engine speeds, the oil level is below the IMS bearing, so removing the rear seal allows oil mist in, not liquid oil.
6)2000 and 2001 engines would be either single or dual row IMS bearings. These years are considered a "transitional period" for the bearing designs, requiring pull the flywheel and looking to determine which bearing is in the engine. In spite of all the drivel posted on the internet, build dates on these years are useless; I personally own both a very early 2000 M96 engine car, and one of the very last produced in 2001, both purchased new during the model year. When I retrofitted both with IMS Solutions, I found the 2000 engine was a single row, while the 2001 was a dual row, which is totally contrary to what the internet thinks should be there.
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Thanks for the information, very interesting.
3) As I mentioned my engine had very little oil in the shaft or the bearing and no grease in the bearing which would be explained by the external seal degradation.
5) That is good to know. Have you had experience with bearings that have had the seals removed? I have never seen anything about them failing from lack of lubrication. This would suggest that the mist is enough, or that the sample is not large enough to be meaningful. I will make a point of keeping the oil level at the highest level.
6) I am aware that there is no guaranteed relationship between MY, serial number and bearing. I was speaking in general terms.
Thanks again for your input.