I know there has been a lot of discussion about the quality of third party aftermarket monovalve cartridges. They don't seem to have as strong a return spring as the genuine MB cartridges and suffer poor performance at high RPMs. Mercedes no longer sells the cartridge, but does sell the complete monovalve.

My cartridge that failed was a genuine MB cartridge. I got the Uro repair kit from Rock Auto. When I first put all the new parts in, the monovalve would not snap in the retracted position. I took the rubber part out and soaked it in almost boiling water for a while to make it more pliable. I reassembled it and it has good snap in both directions.

The part number for the Uro kit is 0008350644R.

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Tom Evans
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