I know this has been discussed at length, however I can't recall seeing the answer to this. So if you would, please bare with me if it has been asked and answered.
My question about the suction pump is this. Can anyone who has replaced one tell me what the proper function is. Specifically, is it supposed to be checked in one direction on both ports or just the one that flows straight through. This would of course compareing the new to the old. Thanks.

 

Anyone?

 

your talking about the SAP pump right? yea it's only supposed to flow one way. it's just to heat up the 02 sensors/cats faster. and wut engine, the 1.8 and 2.8 piping is diff

 

It's this part I'm refering to.
VW/AUDI P/N 058 133 753 B

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