Was looking at a 2005 today and upon start up, I noticed an air sound. The source was what looks to be an air pump -driver's side, front of engine, runs off drive belt. Is this stock or is it after market for some reason? Truck has a pacbrake exhaust brake if that helps. Any ideas?
Andy

 

As far as I know, Pacbrake has an electric pump, not belt-driven. That sounds like the pump for a Jacobs exhaust brake. Sounds like maybe the previous owner mixed and matched parts to me.

 

Thanks. It is a Jacobs exhaust brake. So that's what it is eh?
Andy

 

Does it look like this?







If so, here's the part #.

 

YES! That's it exactly.

 

It is a vacuum pump. The Jacobs brand runs off vacuum instead of air pressure. Those little vacuum pumps are spendy, make sure it is operating properly before you buy the truck......

 

Are they supposed to be noisy?

 

Call Cummins with the part #.
It's been a few years, but I think the part was less than $150.00.

 

Cummins price is $215.41 + tax.

 

IDK if they are normally noisy or not. How bout it, anyone that runs the Jake, are the vacuum pumps normally noisy??