Identify this part...

Can the 2.3T experts please tell me what this round part is that is attached to the lower right hand side of the valve cover?
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Attachment 16561

This part is missing from my (new to me) 2004 9-5 Arc. I noticed a small oil leak where this part should be and happened to see threaded inserts and figured something should bolt up to this spot. While I was at my local U-pull yards looking for random parts I started looking at motors to see if anything was bolted here and sure enough, this part in the photos is attached to a junk car out there and I need to identify what it is. It must not be a critical part as my engine runs great and I do not throw any codes but I need to know what this is. The small oil leak might be simply coming from the valve cover gasket as this is right at one of those half moon shapes, but I'm just confused as to why the one on my car has been removed.

Please let me know what this is. Thank you!

It's a mechanical vacuum pump and was used on the earlier model years with automatic transmission. I guess Saab figured out it wasn't really needed and later models didn't have it anymore. I can't recall the year they eliminated this part but my 2005 9-5 with AT didn't have it.

If there is a leak where you indicate, replacing the valve cover gasket will most likely fix that.

From the WIS:

To increase the braking effect on Saab 9-5 2.0 and 2.3 with automatic transmission, these cars have been equipped with an additional vacuum pump. The pump provides the brake servo with negative pressure when the engine is unable to supply this fully.

The pump is ring type, mounted on the cylinder head and driven by the camshaft. Since it is connected to the camshaft, the speed of the pump is half that of the engine, and negative pressure is produced continually for the brake system.

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