Never forget that when we replace wheel bearings we do it by weight. Put the recommended weight ( ounces not viscosity) in the bearing. Also, this is partly because the grease will heat and become more liquid. The correct amount of grease will insure that the bearing is always lubricated. If grease has hardened, leaked out, etc you will have less in the hub to lubricate. As is heats and moves around in the hub ( albit not a lot of moving and melting) but it can provide the needed lubrication that is missing until the existing grease warms and moves possibly into the bearing more effectively. Not a guarantee, but it is a possibility.

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red