Chevrolet 10 Series 1970 Service Manual page 362

ENGINE COOLING 6K-2
Upon repeated coolant lo s s , the p ressu re rad iator cap
and seat should be checked fo r sealing ability.
cooling system should be checked fo r loose hose connec­
tions, d efective hoses, gasket leaks, etc.
Coolant System Checks
1. T es t fo r re s tric tio n in the rad iator, by w arm ing the
engine up and then turning the engine o ff and feelin g
the rad iator. The ra d iator should be hot at the top
and w arm at the bottom , with an even tem perature
ris e fro m bottom to top.
indicate clogged sections.
2. W ater pump operation may be checked by running the
engine while squeezing the upper radiator hose.
pressu re surge should be felt.
vent-hole in pump.
NOTE: A d efective head gasket may allow ex­
haust gases to leak into the cooling system .
This is p a rticu la rly damaging to the cooling
system as the gases com bine with the w ater to
fo rm acids which are harm ful to both the ra d ia ­
to r and engine.
3. To check fo r exhaust leaks into the cooling system ,
drain the system until the w ater le v e l stands just
above the top o f the cylin d er head, then disconnect
the upper ra d ia tor hose and rem ove the therm ostat
and fan b elt. Start the engine and quickly a ccelera te
s e v e ra l tim es. At the sam e tim e note any a p p reci­
able w ater ris e o r the appearance of bubbles which
are indicative of exhaust gases leaking into the co o l­
ing system .
Periodic M aintenance
It is the ow n er's resp on sib ility to keep the fr e e z e p r o ­
tection at a le v e l com m ensurate with the area in which
the veh icle w ill be operated.
system p rotection should be maintained at lea st to 0 °F .,
to p rovid e adequate c o rro sio n protection.
solution due to lo ss of coolant fo r any reason or in areas
where tem p eratu res lo w e r than -2 0 ° F. may occu r, a
su fficien t amount of an ethylene g ly c o l base coolant that
m eets GM Specification 1899-M should be used.
In a reas w here a n ti-fr e e z e is not requ ired , adequate
engine system co rro sio n protection may be maintained
by using a co rro s io n inhibitor which m eets a ll re q u ire ­
ments o f GM Specification 1894-M.
E v e ry two yea rs the cooling system should be s e rv ic e d
by flushing with plain w ater, then com pletely r e fille d with
a fre s h solution o f w ater
(perm anent-type) g ly c o l base coolant m eeting GM Speci­
fication 1899-M, and providin g fre e z in g p rotection at
lea st to 0 °F . At this tim e, also add GM Cooling System
Inhibitor and S ealer or equivalent. In addition, C ooling
System Inhibitor and S ealer should be added e v e ry fa ll
th erea fter. GM C ooling
form ation of rust o r scale and is com patible with alum i­
num components.
NOTE: A lcoh ol o r methanol base coolants or
plain w ater a re not
cooling system at any tim e.
Tw o common causes o f co rro s io n a re : (1) a ir su ction --
A ir may be drawn into the system due to low liquid le v e l
in the rad iator, leaky w ater pump o r loose hose connec­
A lso , the
Cold spots in the radiator
Check fo r a plugged
R ega rd less of clim ate,
When adding
and high-quality inhibited
System Inhibitor retards the
recom m ended fo r your
tions; (2) exhaust gas leakage--E xhau st gas may be blown
into the cooling system past the cylin d er head gasket or
through cracks in the cylin der head and block.
Cleaning
A good cleaning solution should be used to loosen the
rust and scale b efo re re v e r s e flushing the cooling s y s ­
tem . T h ere are a number o f cleaning solutions available
and the m anufacturer's instructions with the p a rticu lar
clean er being used should always be follow ed.
An excellen t preparation to use fo r this purpose is GM
C ooling System Cleaner.
cleaning the system applies only when this type clean er
is used.
A
1. Drain the coolin g system including the cylin d er block,
and then close drain plugs.
2. Rem ove therm ostat and rep la ce therm ostat housing.
3. Add the liquid portion (No. 1) of the cooling system
clean er.
4. F ill the cooling system with w ater to a le v e l of about
3 inches below the top of the o v e rflo w pipe.
5. C over the radiator and run the engine at moderate
speed until engine coolant tem peratu re reaches 180
d egrees.
6. R em ove c o v e r fro m rad iator and continue to run the
engine fo r 20 minutes.
7. W hile the engine is s till running, add the powder
portion (No. 2) o f the cooling system clean er and
continue to run the engine fo r 10 minutes.
8. At the end of this tim e, stop the engine, wait a few
minutes and then open the drain cocks. A ls o , rem ove
lo w er hose connection.
CA UTIO N: Be carefu l not to scald your hands.
NOTE: D irt and bugs may be cleaned out o f the
radiator a ir passages by blowing out with a ir
p ressu re fro m the back o f the c o re .
rad iator fins.
Reverse Flushing
R ev e rs e flushing should always be accom plished a fter
the system is thoroughly
Flushing is accom plished through the system in a d ir e c ­
tion opposite to the norm al flow .
w ater to get behind the c o rro s io n deposits and fo rc e
them out.
Radiator
1. R em ove the radiator upper and lo w e r hoses and r e ­
place the rad iator cap.
2. Attach a lead-aw ay hose at the top of the radiator.
3. Attach a new piece of hose to the rad iator outlet
connection and in sert the flushing gun in this hose.
4. Connect the w ater hose o f the flushing gun to a water
outlet and the a ir hose to an a ir line.
5. Turn on the w ater and when the ra d ia tor is fu ll, turn
on the a ir in short blasts, allow ing the ra d ia tor to f ill
between blasts of a ir.
CAUTIO N: Apply
rad iator w ill
6. Continue this flushing until the w ater fro m the lead-
away hose runs clea r.
Radiator Cap
The rad iator cap should be washed with clean w ater and
p ressu re checked at regu lar tune-up in terva ls.
The follow in g direction s fo r
A void boiling.
Do not bend
cleaned as outlined above.
This action causes the
a ir gradually as a clogged
stand only a lim ite d p ressu re.
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