Chevrolet 70 1969 Series, Руководство по ремонту

Страница: 207 / 913

BRAKES 5A-14
becomes so laden with dirt, that tapping it against
some solid surface (such as a workbench) will
not remove foreign matter, then a new cleaner
should be installed.
The air cleaner on the tilt cab models is lo­
cated on the back side of the front bumper near
the vacuum power cylinder and is accessible by
tilting cab forward (see fig. 11).
The air cleaner on the conventional models is
located in the left rear corner of the cab, directly
behind the driver's seat. To remove, unfasten nut
and bolt holding cleaner to bracket and pull cleaner
off air hose (see fig. 12).
VACUUM CHECK VALVE
On all vehicles with vacuum power assisted
hydraulic brakes a check valve is used somewhere
in the vacuum line between the engine intake
manifold (gasoline) and the vacuum power cylinder
(see fig. 13).
Purpose of check valve is to seal vacuum in
power cylinder (and in vacuum reserve tank, when
used), assuring sufficient vacuum for at least one
power brake application in case the engine stalls.
Check valve can be tested for leakage by dis­
connecting power cylinder vacuum line from valve
fitting and connecting a vacuum gauge, using a
length of hose between gauge and check valve.
Start engine, run at idle for a few seconds, and
note reading on gauge. Stop engine and observe
rate of vacuum drop. If drop exceeds 1 inch in 15
seconds, leakage must be considered excessive,
and check valve must be repaired or replaced.
There are two basically different type vacuum
check valves used. One is repairable and one is
not. The repairable type has a cast metal body
and is used on all tilt cab model trucks.
The non-repairable type has a sealed plastic body
and is used on all conventional cab models.
Removal and installation of all valves is the
same. Disconnect all lines and hoses and remove
bolts or screws which fasten valve to vehicle.
Discard malfunctioning valves removed from con­
ventional cab models and replace with new valve.
Valves removed from tilt cab models can be
repaired.
Valve on conventional models is located in the
engine compartment and is fastened to a bracket
attached to the fire wall (see fig. 13).
Valve on the tilt cab model is at the front of
the engine and is mounted on a bracket attached to
the frame crossmember on Diesel models. On gas­
oline models, the valve is fastened to a bracket
which is bolted on cab rear support, inside the
channel on left-hand side (see fig. 13).
Figure 13— Vacuum Check Valves Installed
CHEVROLET SERIES 70-80 H EA V Y DUTY TRUCK SH O P M A N U A L