My limited experience with Airtex stems from installing AC-Delco water pumps on American cars. (Airtex makes AC's and Carquest's new water pumps) They lasted a long time. They worked well. They were expensive, when compared to their rebuilt rivals. They are still, as far as I know GM Factory Installed on all new GM cars and trucks. That says a little something, right there. That having been said, I have never heard of one being put on a MB. So, I just don't know how that would work out.
God Bless,
Dave.

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Currently Driving:
1986 Mercedes Benz 560SEL
1994 Lincoln Town Car
1994 Cadillac Deville
1985 Lincoln Town Car- Retired

The Official Car of a Realtor- Lincoln Town Car
The Official Car of the Successful Independent Insurance Agent- Mercedes Benz S Class