PREVOST LE MIRAGE XLII BUS SHELLS, Maintenance Manual

Page: 96 / 1260

Section 05: COOLING SYSTEM
PA1564
8
Recommended phosphate free coolants:
•
Prevost #685125;
•
Detroit Diesel “DDC Power Cool” (P/N
23512138);
•
Prestone AF977 (bulk), 72702 (3.78 L),
70119 (205L), 70102 (4L).
5.6 INHIBITORS
A coolant solution, which has insufficient
inhibitors or no inhibitors at all, invites the
formation of rust, scale, sludge and mineral
deposits within the cooling system. These
deposits can cause water pump seal wear and
coat the interior of coolant system passages.
Heat transfer is reduced as deposits build up,
leading to an overheating condition. Continued
operation with this condition can lead to serious
engine damage: liner scuffing, scoring, piston
seizure and cylinder head cracking. These
damages can occur quickly or over a longer
period of time, depending of location and
amount of deposits. Improperly inhibited
coolants can become corrosive enough to "eat
away" coolant passages and seal ring grooves
and cause leaks to develop. Hydrostatic lock
can occur if leak is internal and accumulates on
top of a piston. The result may be a bent
connecting rod. Cavitation erosion may occur in
improperly inhibited coolants. Cavitation erosion
is caused by the implosion of tiny bubbles
against localized surfaces of the system. Such
implosion causes pinpoint pressures high
enough to erode pump impellers, cylinder liners
and cylinder blocks. In extreme cases, their
surfaces are so deeply pitted that they appear to
be spongy, and holes can develop completely
through them.
5.6.1 Inhibitor Test Procedures
Test Kits are commercially available to check
engine coolant for nitrite concentration. Nitrite
concentration is an indication of Supplemental
Coolant Additive (SCA) level. Nitrite must be
maintained within recommended levels. Coolant
must be tested at each oil change to insure that
inhibitor levels are maintained within the ranges
shown hereafter:
NOTE
Above SCA values with Detroit Diesel #7se298
or TMC RP-329 “Type A”. Use Nalco Chemical
Company nitrite test kits (CO-318). A factory
coolant analysis program is available through
Detroit Diesel distributors under part number
23508774.
DDC Fully Formulated Glycol Coolant Limits
-30 -– 50(°F) Freeze Point (°F)
125 -– 500 ppm Boron (ppm)
800 -– 3200 ppm Nitrite (ppm)
200 -– 750 ppm Nitrate (ppm)
50 –- 250 ppm Silicon (ppm)
0 ppm MAX Phosphorus (ppm)
8.0 -– 11.0 pH
40 ppm MAX Chlorides (ppm)
100 ppm MAX Sulfates (ppm)
5.7 COOLANT RECOMMENDATIONS
1. Always use recommended antifreeze,
inhibitor and water at proper concentration
levels. A 50% coolant/water solution is
normally used as factory fill. Antifreeze
concentration over 70% is not recommended
because of poor heat transfer capability,
adverse freeze protection and silicate
dropout. Antifreeze concentration below 30%
offers little freeze, boilover or corrosion
protection.
2. Use only ethylene glycol antifreeze meeting
the Detroit Diesel #7se298 or TMC RP-329
“Type A” formulation.
3. Use an antifreeze solution year-round for
freeze and boil-over protection. Seasonal
changing of coolant from an antifreeze
solution to an inhibitor/water solution is
recommended.
4. Pre-mix coolant makeup solutions at proper
concentrations before adding to the cooling
system.
5. Maintain the prescribed inhibitor strength
levels as required.
6. Do not mix different base inhibitor packages.
7. Always maintain proper coolant level.