You didn't say what year truck you have. Get and Assembly Manual from the
parts vendors. It has all the models and how it goes together, lines, hoses,
big parts with all pictures/drawings. Not much text, some part numbers. You
have to know what model truck you have, such as 4000 or 6000 series for
2-tons. The Hydro is a seperate unit under cab, sometimes on pass side,other
times just under door on drivers side or even in center area of frame under
cab. Some nice cars like Buicks, Olds, and Cads had a unit that went on
steering column just on engine side of firewall, connected to the brake
pedal with linkage. Not sure if ever used on trucks like that. Was option on
3/4-ton according to guys on list, haven't ever seen one myself. Basically
one brake line from master and two going out of Hydro for front and rear
systems. Big vac line (steel and hose) goes to vac canister and hose comes
out of it for a breather which is usually up in cab back corner. This
breather allows you to hear the "hiss" as you let off the brakes when
driving. There is another master cylinder (slave?) on the hydro unit, the
part that goes bad alot. and big leather diaphragm in canister that also
dries out and leaks causing the system not to work. The brakes will work
manually if Hydro doesn't work, just press harder at pedal.
G. L. Perry
54 Chevy 2-ton (driver)
50 Chevy COE (project)
55 GMC COE (project)
MM Jet Star 3 (tractor)
----- Original Message -----
Sent: Saturday, March 31, 2001 12:33 AM
Subject: [oletrucks] Hydrovac??? I'm confused.
> OK, I think I am thoroughly confused. I found a sketch in my chevy truck
> data book of a "vacuum booster". In this sketch the unit is located
> behind the MC on the driver's side and appears to run on a mechanical
> with the brake pedal. What I have on my 2-ton is actually located on the
> passenger side frame rail and has no mechanical linkages, just vacuum and
> hydraulic lines. What exactly is a hydrovac unit? Is what I have not a
> hydrovac unit? What should one look like? Does someone have a schematic
> the correct line hookups for one of these units? The data book also
> to single and dual line boosters....again I am confused?
> Any responses would be greatly appreciated. I am now thinking that the PO
> may not have even had this unit hooked up correctly at all.
> Thanks Neil
> 46 2-ton.
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959