6.5 diesel serpentine belt

My 6.5 threw it serpentine belt. Water pump, alternator, idler, AC all turn freely. to the passenger side , left of the water pump and crankshaft is a pulley I can't identify. Looks like a vacuum pump.
Anybody know what it is? It does not turn more than 1/8 rotation.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Greetings,
It a vacuum pump. Unfortunately I can't remember if it should turn freely or not, but I don't think it will. The center shaft is connected to a cam lob which moves a piston to pull a vacuum. There is supposed to be a certain amount of synthetic oil inside the cam case and it is possible for a pump to fail (I had to replace mine on my former '95 C1500 with the 6.5L TD)
That's about all I can offer right now - Jonathan

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The pump should turn by hand, but with alternating difficulty as the lobe compresses the spring for the diaphragm. Go to your local parts store and ask to check out a replacement pump for comparison.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.