Chevrolet DB90 Series, Service Manual

Page: 239 / 242

Sec. 13-233
RADIATOR AND SURGE TANK
IMPORTANT
The cooling sy ste m should be checked when it is cool, but if the cap m ust be
rem oved when the engine is at norm al or above tem perature, a cloth should be
p laced over the cap. The cap should then be rotated counterclockw ise without p r e s s ­
ing downward until the r e lie f position is reached. The p r e ssu r e m ust be allow ed to
escap e com p letely. T his may take som e tim e for a large engine. The cap should
then be d ep r esse d and rotated again counterclockw ise to the rem oval p osition .
R A D IA TO R SHUTTER AIR CYLINDER
V eh icles equipped with radiator sh u tters, u se
an a ir cylinder of type shown in figure 6. The
cylinder is designed with b u ilt-in o v e r -tr a v el
fea tu res and does not require p eriod ic adjustment
or m aintenance.
For a ll other inform ation on sh u tters and
c o n tro ls, refer to RADIATOR AND SURGE TANK
(SEC. 13) page 13-7 of S ervice Manual ST 135-70.
COOLING SYSTEM NOTES AND PRECAUTIONS
1. O verheating is not alw ays caused by a d efective coolin g sy stem ; in co rrect
ignition tim ing, dragging b rakes, under-inflated tir e s , and im proper u se of tr a n s­
m issio n g e a r s can c a u se overheating.
2. Keep w ater pump and fan d rive b elts at proper tension. R efer to ENGINE
COOLING SYSTEM (SEC. 6K).
3. Do not o v e r -fill cooling sy ste m . Expansion of coolant when hot w ill cau se
lo s s of coolant through overflow tube.
4. Do not rem ove radiator f ille r cap when engine is hot. Wait until sy ste m
c o o ls off.
5. Do not pour cold w ater into cooling sy ste m when the engine is hot. Wait
until sy ste m c o o ls off.
6. If coolin g sy ste m req u ires frequent refillin g , check for lea k s.
7. Keep a ll connections tight, and make su re gask et on radiator fille r cap is
in good condition.
8. When fillin g sy ste m with a n ti-fr e e z e solution ALWAYS FOLLOW RECOM­
MENDATIONS of a n ti-fr e e z e m anufacturer.
9. U se only Ethylene G lycol b ase coolant m eeting GM Specification 1899-M . DO
NOT u se G lycol Ether (Methoxy Propanol Type) in T oro-F low II Engines.
10. Drain and flush cooling sy ste m every other yea r, p referab ly at the b egin ­
ning or end of w inter operation.
R efer to next page for "Specifications."
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT