air dryer

I have 1978 s series with a 290 cummins .It has a air dryer behind the cab on drivers side that cycles constantly and makes a hammering sound. Is this normal?

No need to post in more than one section.

What brand is the thing? I never heard an air dryer make a noise as you say,had them constantly dump and make the compressor kick on and off... All they needed was servicing. If it's a Bendix AD2 or 4 it may need a fresh desiccant filter element. If it's a CR BrakeMaster they just have a washable steelwool like filter. Not sure about Cycloguard's or if IH used them.
Did you try bypassing the dryer to determine it's the cause of the sound?

1st the air drier cycles via a signal from the governor, the air governor responds to pressure via a line from the "wet tank". Be careful not to blame the drier for problems elsewhere.
What compressor is on the engine? is it a two cyl Bendix or a single cyl Holset?
You can bypass the drier by connecting the two big lines together.
The correct way to diagnois is to check pressures on the res line on the governor and also on the wet tank.
what do the pressure gauges inside the truck show?
The drier should have a check valve in the outlet.
Line can leak along their leinth and make no sound, spray them with soapy water and they will foam along their leinth.
I've had AD-9's where the filter has worked loose or the threads in the base are worn, and the filter will hit the outside cover and make a knocking sound.