Testing Vac Pump

[HBP]

I've read a number of threads related to the 2404 code and testing the mechanical vac pump on the rear of the pass side cyl bank, but haven't been able to determine which of the two ports on the pump to connect the vac gauge to?  '08 Cayenne S.  There's a smaller barbed 90 degree fitting with a rubber hose that's pushed on, and there's a larger fitting with a larger plastic vac hose and a connector that has to be squeezed at the base to remove it from the pump.  Any info on which to use would be appreciated.

Edited March 14, 2017 by HBP

[Doug_B_928]

I don't know much about this but I'll chime in given no one has responded to your query.  I hooked a mighty vac to the smaller fitting (mine has a T in the hose that comes off of that fitting with a cap on it that one can pull off to put a vacuum tester on).  I'm not familiar with the code you're getting.  When I put my mityvac on that fitting with the engine idling it read -75psi.  I was looking to see if the vacuum was steady, which it was; I had been told that a fluctuating vacuum indicates a leak. 

[HBP]

Thanks for the reply Doug.  I'd read that the reading on a good pump is supposed to be about 20 in Hg.  When I first tested the small port, I did as you and removed the cap on the T and the gauge switched rapidly between vac and pressure (this gauge reads both).  So I went directly to the fitting on the pump and got the same reading.  Then I checked the large port and got a fairly steady reading of 25 in Hg.  

 

Apologies, there was a keystroke error in my first post, the error code is 2404

Edited March 14, 2017 by HBP

[Doug_B_928]

From what I recall one should test from the little barbed fitting and it should have a vacuum of .5 bar (which I think is about 15 in Hg).  My wife just got home with the car so I put my mityvac on the T for that goes to the smaller fitting on the vacuum pump and I got a reading of 26 in Hg, rock steady. 

[HBP]

Thanks very much for taking the time to do that Doug, good of you and I really appreciate it.

 

Based on your result it looks like a new pump is in order.