Unloader Valve not hissing when compressor shuts off

by Tom
(South Carolina)

Very old Quincy compressor

Very old Quincy compressor

Recently I had the head of a very old Quincy compressor rebuilt. Once problems with bolts attaching the head were resolved, the compressor works fine with a couple of exceptions.


Now it takes a long time to load and the air drains quickly and recharges slowly.

Once the tank is full and the compressor cuts off the customary hiss is not present.

Could these problems be related? How do I know what unloader valve I need?

This compressor was apparently purchased in the 60's and has not been used in 25-30 years.

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Apr 05, 2018
Unloader?
by: Doug in s.d.ca.

Old Gilbarco? It was hissing before?

Sounds like unloader's stuck partly open. Can't tell from the pic (same one twice).

You've got a leak somewhere. Gotta find it to fix it...
Sure the head's not leaking? Discharge pipe? If none of that, then unloader, probably, but still need to see it, around where the air is coming from.

(Duplicate image removed - Moderator)

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