Chevrolet DB90 Series, Service Manual

Page: 93 / 242

SECTION 6K
Cnqine GoolUuf Sy&tem
Information pertinent to truck m odels covered by this supplem ent is the sam e
as explained in ENGINE COOLING SYSTEM (SEC. 6K) in Heavy Duty Truck S erv ice
Manual ST 135-70 and Supplement ST 332-71, except as indicated by the follow ing
inform ation which is eith er new or supplem ental in nature.
R eferen ce should be made to RADIATOR AND SURGE TANK (SEC. 13) in this
supplem ent for inform ation regarding radiator mounting, radiator core and surge
tank and cooling sy stem fille r cap.
NOTE: For cooling sy ste m inform ation related to Cummins Engine that is not
covered in th is supplem ent, r e fe r to appropriate Cumm ins S erv ice P ublication.
COO LIN G SYSTEM GENERAL
MAINTENANCE
A ll v e h icle s covered by th is supplem ent are
equipped with p r e ssu r e type radiator fille r caps.
Most veh icle cooling sy ste m s have a 9 p si
p r e ssu r e cap. T h ese 9-pound p r e ssu r e caps are
stam ped R C -12-9.
Other cooling s y ste m s have either 1 3 -p si, or
1 5 -p si p r e ssu r e cap s. The 13-pound cap is stam ped
eith er R C -12-13 or R C -3 5 -1 3 . Stamping on 15 p si
p r e ssu r e cap is R C -1 5 -1 5 .
COOLING SYSTEM PRESSURE CHECK
S everal types of cooling sy ste m p r e ssu r e
checking d ev ices a re available lo ca lly and manu­
fa c tu r er's in stru ction s should be follow ed for
p roper u se . A typical te s te r is illu strated in fig ­
u re 1 and usual procedure is given below for mak­
ing te st of p r e ssu r e cap and cooling sy stem .
1. T estin g Radiator Cap
CAUTIO N : The radiator cap should
not be removed while the engine is at
normal operating temperature. If it is
necessary to remove the cap while the
engine is hot, fir s t relieve the pressure
in the system by turning the radiator cap
counterclockwise to firs t stop, using cau­
tion not to scald hands. Push down on cap
and turn counterclockwise to remove cap.
a. With radiator fille r cap rem oved, w et the
cap gasket with w ater and w ash off any sedim ent
from sea lin g su rface, then in sta ll cap on te s te r .
b. Pump up p r e s s u r e by operating pump plung­
e r handle. When the p r e ssu r e stam ped on cap is
reached, o b serve te s te r dial and note the rate of
d e cr e a se in p r e ssu r e .
c . The indicator hand on gauge dial should
rem ain within the corresponding p r e ssu r e segm ent
of sc a le for approxim ately 10 secon d s. If p r e ssu r e
cap does not m eet th is requirem ent it should be
rep laced with new cap.
2. T esting Cooling System
a. Tighten all radiator and heater hose clam ps.
A lso , check other connections for leak s at a ir co m ­
p r e s s o r coolant lin e s , etc.
b. F ill cooling sy ste m to le v e l of fille r cap
sea t.
c. Attach te s te r to fille r neck follow ing the
in stru ction s supplied with te ste r .
d. B uild p r e ssu r e up to 20 p s i. (m axim um ).
e. The cooling sy ste m should hold the 20 p si
p r e ssu r e for approxim ately two m inutes. If p r e s ­
su r e drops appreciably in l e s s than two m inutes, a
leak in sy ste m i s indicated.
Figure I—Typical Use
of
Cooling System Tester
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT