procedures and any specifications, clearances, or
outlet to the radiator if necessary, and remove the outlet
retaining cap screws. The thermostat can then be
tolerances pertinent to the job.
removed and checked for condition and operation. If it
When you replace a pump, install a new gasket.
is excessively rusted or bent, or if the valve is not
Make sure the mating surfaces are clean and smooth.
tightly closed, the thermostat must be discarded.
The application of sealer to both sides of the gasket is
If the thermostat appears to be in good condition,
often recommended. Then, after refilling the system,
its operation can be tested, as shown in figure 5-11.
the pump should be checked for leaks, noise, and
The thermostat is suspended in a container of water
proper operation.
together with a high-temperature thermometer. Then,
Fan and Belt
by heating the container on a stove or hot plate, the
temperature at which the thermostat begins to open, as
A bent or distorted fan or one with a loose blade
well as the full-open temperature, can be determined.
should be replaced. Where the fan is merely loose on
If the thermostat fails to respond at specified
its mounting, you can tighten it. Loose fan belts can be
temperatures, it should be discarded. Specifications
adjusted for proper tension, usually by shifting the
vary on different vehicles, but on one popular make,
generator on its mounting. A common method for
the opening temperature is 180 to 185F, and the
measuring belt tension is to press down on the belt at a
full-open temperature is 200 to 202F. If the tests are
point midway between the generator and fan pulley;
satisfactory, the thermostat can be reinstalled. A new
then measure the amount of deflection. The amount of
gasket, or gaskets in the case of some V-8 engines,
d e f l e c t i o n w i l l va r y a n d s h o u l d b e s e t t o t h e
should be used and the cap screws tightened to the
m a n u fa c t u r e r 's s p e c i fi c a t i o n . T h e a m o u n t o f
specified torque. Then, the cooling system can be
deflection will depend on whether the belt is new or
filled and the engine operated to check for leaks as well
used and the distance between the pulleys. The normal
as proper thermostat action.
adjustment of the belt is measured between the two
You should now have a good understanding of the
pulleys furthest apart. The belt should have no more
service and repair requirements that pertain to cooling
than one-half deflection between the two pulleys.
systems in general. However, it is good to remember
A belt adjustment that is just tight enough to
that specific procedures or those peculiar to the system
prevent slipping may be considered correct. A belt that
on a particular vehicle will require reference to the
is too tight can cause the generator or alternator
bearing to wear rapidly. A belt that is too loose may
squeak when the engine is accelerating. When a belt is
misaligned, a squeak may occur at idle speed.
Correction can be made by using spacers on the
accessories or by filing brackets. However, if the
squeak is caused by a non-uniform groove or eccentric
pulley, the pulley should be replaced.
Replacement of a defective belt is usually made by
185
loosening the generator mounting bolts and the
generator adjusting arm and moving the generator
closer to the engine. The belt can then be removed over
the fan and a new one installed and adjusted.
Thermostat
There are no repairs or adjustments to be made on
the ordinary thermostat. The unit must be replaced if it
fails to operate properly. The temperature at which the
thermostat opens is very important and should be
t e s t e d w h e n eve r t h e c o o l i n g s y s t e m o p e r a t i n g
temperature indicates the need. To remove the
ASf05011
thermostat, drain the coolant until its level is below the
Figure 5-11.--Testing a thermometer.
thermostat, remove the hose connecting the thermostat
5-14
