I have to replace the seal between the PS pump and vacuum pump, Im wondering if anyone has heard of the vacuum pump going bad and making noise kind of like a ticking/ chattering sound? Im pretty sure its not the lift pump or OF valve making noise as I have held the primer button in and pinched off the return line and doesent make a difference in sound. This noise is getting more noticable as the leak gets worse and is real noisy when under the engine while its running, and rolling down the hiway it sounds like piston slap. I lokked at some internal pics of the vac pump and its just a rotary eccentric pump so I dont see how it could make this wierd noise but I guess anythings possible. Ive been chasing this noise for a while now and its starting to get to me so any opinion or comments on my noisy pump theory are welcome.

 

My only thought would be that the 3 vanes inside the pump are somehow sticking in the slots. Then they slap the outside of the housing when centrifical force makes them slide back out. You will understand what I am talking about when you have the pump off and see it. I don't know if this can even happen. Could it be a bad bearing in the pump? Mabey that is why it is leaking.

 

thanks for the response, I didnt think about the vanes maybe sticking. I gotta hunch im gonna have to pull it off and look at it close. maybe get a reman just in case, kinda pricey though but I can always return it or try to find a kit for it and just rebuild it.

 

I think it is more likely the lift pump. I have read that the primer button pump is separate from the cam lobe pump. I have one in the garage, I could disassemble it I suppose. Do you have access to a stethascope? You do know that Cummins sells a seal kit for about $10, right? Part # 4089742. I've replaced the seal on mine 3 or 4 times, but the vac pump is the original.

 

GAmes, thanks for the seal part #. I will give them a call. If you have that many miles on your vac pump then i dont really think mine is bad since I do have good brake response but do have the noise I cant seem to find. I was just wondreing how many people have had the pump go bad and if it got noisy when it did, thanks for the response.