Saab SONETT III Service Manual page 43

COOLI NG SYSTEM
Radiator with connections
Draining the cooling system
1. Remove the expansion tank cap.
2. The coolant is first drained off through the drain valve
in the lower part of the radiator. If the cooling system
is to be drained completely, also loosen the two hexa-
gon plugs, located one on each side of the lower part
of the engine block.
3. If the cooling system is to be thoroughly drained, the
heat control on the fresh-air heater should be set at
maximum heating.
Refilling the cooling system
Coolant is poured in through the opening on the expan-
sion tank. The heat control should meanwhile be set at
maximum heating and the bleeder nipples on the heat
exchanger and on the thermostatic housing should be
opened, thus
enabling the system to be filled completely.
When the cooling system has been completely filled,
start the engine and run it at varying speeds for a minute
or so, or until coolant emerges through the open bleeder
nipples on the heat exchanger. When this occurs, close
the nipples.
If necessary, pour additional coolant into the expansion
tank and then replace the cap.
Only clean coolant may be used. Never pour in a large
amount of cold coolant while the engine is hot, as this
could cause the cylinder block to crack.
Check the level in the expansion tank after driving for a
few days, as complete venting is achieved only after the
system has been warmed up and cooled down a few times.
Use a recommended coolant only.
6. Flush the system again with clean water, treating the
engine jacket and radiator separately. This time, flush
against the normal direction of coolant flow, Le. flush
the engine jacket from the cylinder head and down-
wards, and the radiator through the lower connection
pipe and upwards.
Before flushing the system this time, back off the upper
water neck and remove the thermostat.
7. Flush the heater element, also against the normal di-
rection of circulation.
8. Check the function of the tap in the line to the heater
element.
9. Ref it the thermostat, water neck and hoses. Test the
system for leaks. When cleaning the cooling system,
also check that the expansion tank overflow pipe is
not choked up with foreign matter. If the cleaning
method described does not suffice to clear all deposits
from the radiator, take the radiator out of the car and
send it to a specialist.
Pressure testing the cooling system for leaks
It is often difficult to discover leakage in the cooling sys-
tem, as the pressure in the system reaches its full value
only while the car is being driven. One good method is to
put the system under pressure with the aid of a pressure
tester, whereupon the radiator, hoses and seals can be
checked. The maximum permissible pressure is 14 psi
(1 bar, kp/cm 2 ).
The opening pressure of the pressure cap can also be
checked with the pressure tester. See specifications in
chapter 0, concerning opening pressures.
Cleaning the cooling system
The cooling system
is
cleaned in accordance with the
following procedures:
1. Drain off the water.
2. Flush the system with clean water.
3. Fill the system with clean water to which a suitable
commercial solvent has been added. Follow the solvent
manufacture's instructions.
4. Shield the radiator and run the engine until warm.
5. Stop the engine and, after waiting a few minutes, drain
off the water.
Testing the radiator for leaks
If the radiator is removed it can be tested for leaks by
seal ing the pipe connections, submerging it in water and
testing with compressed air at max. 14 psi (1 bar, kp/cm 2 ).
A leaky radiator can be repaired by soldering. Patent
sealers which are added to the cooling water should be
used only in emergencies. These compounds can choke
jackets and pipes and impede circulation. The cells of the
radiator core may at times be so clogged up with dust,
smashed insects, etc., that the air flow is reduced. The
core must then be washed and blown clear with com-
pressed air.
Nov. 1972
SAAB
261-1