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Inhibitor Test Procedures
Engine coolant must be tested for
required inhibitor levels at the intervals
shown on the "Coolant Test Intervals"
chart. Test kits and test strips are com-
mercially available to check engine
coolant for nitrite concentration. Inhibitor
levels must be maintained within the
ranges shown on the following chart:
Detroit Diesel
Maintenance Products System
Min.
Max.
PPM
PPM
Boron (B)
1000
1500
Nitrite (NO2)
800
2400
Nitrates (NO3)
1000
2000
Silicon (Si)
50
250
Phosphorous (P)
0
500
pH
8.5
10.5
Selected Products Supplemental Coolant
Additive Values with GM6038-M or
ASTM D 4985 (50/50 Glycol/Water Mixture)
Coolant test strips that measure
glycol and nitrite concentration are
available from authorized Detroit
Diesel service outlets under part
number 23515917. A factory coolant
analysis program is also available
under part number 23508774.
Silicate/Phosphate Dropout
Excessive amounts of chemicals in the
engine coolant can cause additive
dropout, which creates a gel-type or
crystaline deposit that reduces heat
transfer and coolant flow.
The gel takes the color of the
coolant in the wet state, but appears
as a white powdery deposit when dry.
Although silica gel is non-abrasive, it
can pick up solid particles in the
coolant and become gritty, causing
excessive wear of water pump seals
and other cooling system compo-
nents. The wet gel can be removed by
using a non-acid (alkali) type heavy-
®
duty cleaner such as Nalprep
2001
(sodium nitrite/sodium tetraborate),
while the dried silicate requires engine
disassembly and caustic solution or
mechanical cleaning of individual
components.
Phosphate can drop out of solution
and crystallize on heat transfer sur-
faces and water pump seal faces.
Phosphate may be removed by flush-
ing the system with water to redissolve
crystals.
The total amount of chemicals in the
coolant can be controlled to desirable
levels by using the referenced
antifreeze at the needed freeze pro-
tection concentration, adding Detroit
Diesel Maintenance Product inhibitors
and water that meets Detroit Diesel
requirements.
NOTICE:
Failure to use and maintain coolant
and coolant inhibitor mixture at suffi-
cient concentration levels can result
in damage to the cooling system and
its related components. Conversely,
overconcentration of coolant and/or
inhibitor can result in poor heat
transfer, leading to engine overheat,
additive dropout, or both. Always
maintain concentrations at recom-
mended levels.
58
For more detailed coolant recom-
mendations, refer to "Coolant Selec-
tions for Engine Cooling Systems,"
form 7SE298, available from autho-
rized Detroit Diesel service outlets.
H. How to Drain and
Flush the Cooling
System
CAUTION:
Do not remove the pressure control
cap from the radiator or heat
exchanger tank or attempt to drain
the coolant until the engine has
cooled. Once the engine has
cooled, use extreme care when
removing the cap. The sudden
release of pressure from a heated
cooling system can result in a loss
of coolant and possible personal
injury (scalding) from the hot liquid.
NOTICE:
An immersion-type engine block heater
may be installed to improve cold
weather starting. Always disconnect
the electrical connections to the block
heater before draining the coolant.
Failure to disconnect electrical connec-
tions before draining coolant may result
in damage to the block heater element
if the heater is switched on without
coolant in the system.
1. With the engine cool, drain the
previous solution from the engine
and radiator or heat exchanger
tank. Dispose of the solution in an
environmentally responsible man-
ner according to state and/or fed-
eral (EPA) recommendations.
2. Refill the cooling system with
clean, soft water and a good
radiator cleaning compound. If
the engine is warm, fill slowly to
prevent the rapid cooling and dis-
tortion of the metal castings.
3. Start the engine and operate it for
fifteen minutes to circulate the
solution thoroughly.
4. Stop the engine and allow it to
cool.
5. With the engine cool, drain the
cooling system completely.
6. Refill the cooling system with
clean, soft water and operate it
for fifteen minutes.
7. Stop the engine and allow it to
cool.
8. With the engine cool, drain the
cleaner residue from the cooling
system.
9. Refill the system with the proper
mix of antifreeze and clean, soft
water.
10. Entrapped air must be purged
after filling the cooling system. To
do this, allow the engine to
warm-up without the pressure
cap installed. With the transmis-
sion or marine gear in neutral,
increase engine speed above
1000 RPM and add coolant as
required. If a water-jacketed tur-
bocharger is installed, vent the
petcock on the water return line
at the turbocharger until a steady
stream of coolant (no air) is seen.
Then close the petcock.
Install the pressure cap after
the coolant level has stabilized at
the bottom of the radiator or heat
exchanger tank filler neck. Fill the
coolant recovery bottle (if
equipped) to the "Full Cold" level,
or no more than one-quarter of its
volume.
59
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