Combines Air in hydraulic lines

Are you certain its airIJ If it's a noise you're hearing, is it in the cab when driving, and it sounds like a car horn going off just outside for a second ot twoIJ If so, I dont think it's air. My 1680 just started doing this this year and I think, but cannot prove it just yet, that it is the prv on the auxilary pump. Or a problem in the stack valve just outside the cab. If you had air in the hydrostatic system, it should make the machine stall foward motion and then lurch foward as the air escapes.

No its not in the cab, you can only hear it if standing outside. It's something in the hydralicis I know. Sorry for the ignorance but what is a "prv"IJ I just put in a new auxilary pump when I had the hydro rebuilt so I don't know. If you think of anything else let me know, in the meantime I'm gonna call my mechanic and pick his brain. thanx Old Pokey Brad

The prv is the pressure relief valve that sits first in line after the aux pump. If your 1680 is a navistar powered one with the steel lines going all the way to the hydro pump, the prv will be mounted to the plate that the pump is mounted on. What are the symptoms you are experiencingIJ Does the machine act different in any wayIJ When it makes this noise, does the steering go badIJ I'm wondering if when you took the side off the combine to replace the hydro pump, you maybe did'nt get a wire hooked back up on the unload auger switches or maybe bumped one of the adjustments, and the pump is trying to keep the auger pulling in or something.

There's really only one symptom, if it's acting up and I go to raise the header it will stop for a fraction of a second (it stops when you hear the noise) then raises fine. I'm pretty sure it wouldn't have anything to do with what I did to the hydro and pump because it did it last year also. thanx again Brad