I'm not familiar with the 190, but my 85 380SE had a smog pump that was shot. I'm talking totally rusted out, with a bad clutch. As I understand it, this thing is useful during warmup only to pump air into the exhaust (not sure here) to reduce emmissions at the cat converter. It apparantly does zip after warm up. So, lucky as I am to live where emissions testing isn't yet mandatory, I removed it, belt, hoses, and all, plugging up the attached connections at the engine.

The 190 may run something else off the same belt, though, I don't know. If so, and you want to remove the pump only, run a tape over the pulleys and get a 3 belts from the parts store, 1 smaller, 1 the length of the tape, and 1 bigger. Return the 2 that you don't need.

If you'll need it for testing, it's easy to remove and inspect. If the internal vanes aren't beat, you probably have a bad clutch, which works like the A/C compressor clutch (and may be interchangeable too). If it squeels all the time, even when the clutch is 'free-wheeling', then you'll likely need to replace a bearing.

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1986 560SL
2002 Toyota Camry
1993 Lexus