MCi Crusader II 1989 Maintenance Manual page 204

Date
1-1-89
Page
6-5
MC-9 MAINTENANCE MANUAL
equire no additional hardware or plumbing.
All inhibitors become depleted through normal operation.
and additional inhibitor must be added to the coolant as
required to maintain original strength levels.
NOTE: Over-inhibiting antifreeze solutions
can cause silicate dropout. Always follow
the supplier's recommendations on inhibi-
tor usage and handling.
SILICATE DROPOUT
Excessive amounts of chemicals in the engine coolant can
cause silicate dropout. which creates a gel-type deposit that
reduces heat transfer and coolant flow. Silicate dropout may
also occur in coolants using extremely hard water and/or
unusually high operating temperatures.
The gel takes on the color of the coolant solution 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 a gritty. abrasive deposit that can
.cause excessive wear of water pump seals and other cooling
system components.
Ir 1I ,s suspected that a coach cooling system has a gelling
problem I indicated by engine overheating or coach underheat-
Ing1. first try to remove the gel in its "wet" condition. Use an
alkaline cleaner (Nalprep 2001 or equivalent) as directed by the
manufacturer. so that the silica-gel is not allowed to dry. If using
the cleaner once does not correct it. repeat the procedure. If
avu1lab1e. ultrasonics 1s another process that can be used to
remove the gel without aamage to cocling system components.
11 s,I1ca-gel has been allowed to dry inside a coo11ng system
component. removing the gel becomes more difficult. The gel
tends to form in low areas of the cooling system. i.e .. radiator
bottom tank or areas within the engine oil cooler. If gel can be
reached for mechanical cleaning (removal of radiator bottom
tank or "rodding" out a radiator core). then that method can be
used
Finally. dried silica-gel may be removed from a cooling
system component by removing that component from the
coacr, and agitating it in a caustic solution. Extreme care must
be taken when handling such caustic solutions. Safety glasses
and protective gloves should be worn. Do not flush engine
cooling system with caustic solutions because damage can
occur to both metallic and non-metallic compoonents.
The following recommendations are made to prevent silica-
geI formation:
• Use antifreeze that meets GM-6038M formulation which
l!m1ts the amount of silicate to 0.1% maximum.
• Use antifreeze solutions at the concentration required for
freeze protection in your operational area. but do not use more
than 67% antifreeze or less than 30% antifreeze.
• Never use 100% antifreeze for make-up coolant. Mix the
make-up solution at the same concentration as the original fill.
• Use corrosion 1nhIb1tor supplements only as required to
maintain proper system protection. The system should be
·ested to determine the need for additional inhibitor. Test kits
and test strips are commercially available to check engine
coolant for corrosion inh1b1tor strength level. Coolant should be
tested to determine-the need for corrosion inhibitor supple-.
ments and the amount required. Do not use one manufacturer's
test to measure the inhibitor strength level of another manufac-
lurer's product. Always follow the manufacturer's recommended
test procedures. New additives Nalcool 3000 with stabil-aid and
Fleetguard DCA4 have been developed to help prevent silicate
dropout and this may be added to the system when need arises.
• As much as possible. avoid using what can be considered
"hard" water when mixinq with antifreeze.
A list of available antifreeze products that meet GM-6038M
is shown below:
Company
Texaco (1)
BASF Wyandotte (1)
International Harvester
(1 )(5)
Old World Trading Co. (1)
Northern Petro-Chemical (2)
Dow Chemical Canada(3l
Houston Chemical Corp. (4)
111
Generally avadaoie ,n U.S.A
Product
2055 (was JC-04)
241-7
LH. Antifreeze
Full Force Advance
All Weather (NPC 220)
731 .
Security (701
l
(21 Generally avaI1ao1e w1th1n iSO-m,le radius of cn,cago
13) Generally ava11ao1e ,n Canada.
14! Generally available ,n nor!heastern U.S A
151 1 H anttlreeze
in
Canada has high s,llcate con1en1
COOLANT FILTERS - GENERAL
Replaceable elements are available with various chemical
inhibitor systems. Compatibility of the element with other ingre-
dients of the coolant solution cannot always be taken for
granted.
Problems have developed from the use of the magnesium
lower support plate used by some manufacturers in their cool-
ant filters. The magnesium plate w,I1 be attacked by solutions
which will not be detrimental to other metals in the cooling
system. The dissolved magnesium· will be deposited m the
hottest zones of the engine where heat transfer 1s rr:iost critical.
The use of an aluminum or zinc support plate m preference to
magnesium Is recommended to eliminate the potential of this
type of deposit
High chloride coolants will have a detrimental effect on the
water-softening capabilities of systems using ion-exchange
resins. Accumulations of calcium and magnesium ions removed
from the coolant and held captive by the zeolite resin can be
released into the coolant by a regenerative process caused by
high chloride-content solutions.