Radiator Maintenance - GMC G Service Manual

6B2-6 RADIATOR
Off-Vehicle Leak Testing
NOTICE: Do not use boll-out tanks or vats or
other tanks that have been used for copper and
br a ss r a d i a t o r s
aluminum/plastic radiators. The flux, acid, and
caustic cleaners remaining in these tanks will
attack the aluminum and cause radiator failure.
A separate test tank containing clean water is
recommended for servicing aluminum/plastic
radiators.
1. Install test fittings or rubber test caps in the inlet and
outlet necks and seal the oil cooler fittings with metal
plugs to protect the cooler and keep the fluid from
running out (figure 6).
2. Attach the pressure tester and gradually apply air
pressure until 138 kPa (20 psi) is attained. Do not
exceed 138 kPa (20 psi). Check the pressure gage to
see if there is a pressure loss. To ensure that there
Check the outside of the radiator for bent fins or signs of
leakage. Repair leaking radiator cores, but do not seal tem­
porarily with a sealer type antifreeze or coolant additive.
Remove any stones between the fins. Clean loose debris
and road film from the radiator core with a quality grease
solvent and compressed air. Direct the stream of solvent at
the front of the core for more efficient cleaning.
To ensure a thorough cleaning, remove the grille, fan
guard and fan shroud.
Remove the radiator cap and look for plugging and scale
on the inside of the tank. Replace a badly plugged radiator.
Test the radiator and system as described in ENGINE
COOLING (SEC. 6B1).
1. Check the coolant level. If low, add recommended
coolant as required.
2. Check the hose connections and tighten the clamps if
leakage is evident. Replace cracked, stripped or cor­
roded clamps.
3. Check the coolant hoses for spongy or checked
appearance. Replace deteriorated hoses or bursting
could occur, which would result in coolant loss and
extensive engine damage due to overheating.
4. Check the radiator core for leaks and for accumula­
tion of dirt which may obstruct the air passages and
reduce heat transfer.
5. Check the surge tank or recovery tank for leaks.
Plastic tanks may develop cracks from damage by
flying objects. Check metal tanks at the weld seams.
6. Inspect the radiator rubber mountings and bumpers
for deterioration and replace as necessary. Check the
mounting bolts, supports, braces, tie rods and stabi­
lizer rods. Components should be securely refas­
tened in place if mounting bolts are missing, loose or
stripped. Also check for damage to the core, side
flanges and supporting components.
when s e r v i c i n g

RADIATOR MAINTENANCE

are no small leaks, run water over the repair area and
look for bubbles (a mild detergent is helpful.)
If a large water tank is available, submerge the radia­
tor and check for air bubbles.
7. Check for clearance between the fan blades, core
and shroud. Check the fan attaching bolts for tight­
ness and that none are missing. Replace the fan if
any blade is bent. The distance between the blades
and shroud should be equal around the perimeter of
the shroud. Adjust as necessary after any adjustment
has been made to the fan or the fan mounting bracket
and hub.
8. Inspect the filler cap seal for evidence of cracking,
separation or deterioration. Replace as required.
9. To assist in maintaining efficient heat dissipation, an
occasional external flushing with water will remove
the majority of dirt accumulation and foreign matter
from between core fins. Direct water under moderate
pressure from behind the core to force debris out in
the opposite direction of its entry. Direct the water
stream in line with the fins to reduce the possibility of
bending them.
RADIATOR INTERNAL DEPOSITS
A radiator that has a dirty, obstructed core or is leaking
will cause the engine to overheat. A scale deposit inside the
radiator is a result of using hard, high mineral content water
in the cooling system. The effect of heat on the minerals in
the water causes the formation of scale, or hard coating, on
metal surfaces within the radiator, thereby reducing the
transfer of heat. Some hard water will produce a silt-like
deposit which restricts the flow of water. This must be
flushed out at least twice a year— more often if necessary.
SCALE REMOVAL
To remove the hardened scale, a direct chemical action
is necessary. A flushing compound at the specified rate of
30 grams per liter (4 oz. per gallon) of radiator capacity
should be added to the coolant water in the form of a dis­
solved solution while the engine is running. Run the engine
for 15 minutes, then drain the solution and flush the system
with clean water.