PeachParts Mercedes-Benz Forum - View Single Post - On a M104 3.2L what is the last pump on the left...?

G-Benz · #2 11-02-2004, 01:18 PM

Assuming "left" staring at the engine...you would be looking at the air pump.

It's only doing it's job in the first few minutes after startup, pumping air into the system to hasten cat warmup so that optimum emissions efficiency can occur quickly. In Europe, the sniffer gets inserted and data analyzed within the first 60 seconds of startup...a far more stringent test than in the US.

In fact, it probably isn't needed for US emissions, except that the missing component would fail the visual portion of the inspection.

When the air pump get old, the most common failure is that the clutch bearings wear out and seize. I believe kits are now available to replace just that, rather than the whole $800+ unit. The bearing are a weird size and can't be procured easily.